Abstracts

1. Plenary - Nucleation and Growth of Rationally Designed Complex Micro-Architectures

Joanna Aizenberg jaiz@seas.harvard.edu

Wim L. Noorduin. School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, United States Kavli Institute for Bionano Science and Technology, Harvard University, Cambridge, MA 02138, United States

The emergence of complex nano/microstructures is of fundamental interest, and the ability to program their form has practical ramifications in fields such as optics, catalysis and electronics. We developed carbonate/silica microstructures in a dynamic reaction-diffusion system that allows us to rationally devise schemes for precisely sculpting a great variety of elementary shapes by diffusion of CO2 in a solution of barium chloride and sodium metasilicate. We identify two distinct growth modes and show how continuous and discrete modulations in CO2 concentration, pH and temperature can be used to deterministically switch between different regimes and create a bouquet of hierarchically assembled multiscale microstructures with unprecedented levels of complexity and precision. These results outline a nanotechnology strategy for “collaborating” with self-assembly processes in real time to build arbitrary tectonic architectures.

2. Self-assembly of uniform polyhedral silver nanocrystals

Peidong Yang p_yang@berkeley.edu

Department of Chemistry Materials Sci Division, University of California Berkeley, Lawrence Berkeley National Lab, CA 94720, United States

While polyhedral nanocrystals have been assembled into ordered superstructures, directing their self-assembly into densest packings requires precise control of particle shape, polydispersity, interactions and driving forces. In this talk I will show that a range of highly uniform, nanoscale silver polyhedral can self-assemble into structures that have recently been conjectured as the densest packings of these shapes. When passivated with adsorbing polymer, these nano-polyhedra behave as quasi-hard particles, and assemble into millimeter sized 3D supercrystals under simple gravitational driving force. Excess polymer in solution induces depletion attractions that can stabilize less dense, ordered packings. In the case of octahedra, controlling polymer concentration allows us to tune between the well-known Minkowski lattice, and a novel packing with complex helical motifs. Such large-scale ordered arrangements of Ag nanocrystals provide many possibilities for designing scalable 3D plasmonic metamaterials with applications including chemical and biological sensing, nanophotonics and photocatalysis.

3. Self-assembly and aqueous phase behavior of surfactin: a peptide-based biosurfactant

Tomohiro Imura t-imura@aist.go.jp

Shintaro Ikeda1, Dai Kitamoto 1,2 Research Institute for Inovation in Sustainable Chemistry, National Institute of Advanced Science and Technology (AIST), Central 5-2, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan (2) Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan

Biosurfactants (BSs) are environmentally friendly surfactants that are abundantly produced from renewable resources by microorganisms. They have numerous advantages including mild production conditions, low toxicity, and multifunctionality compared to synthetic surfactants. Among a variety of BSs, we focused on surfactin having a unique cyclic peptide moiety, produced by Bacillus subtilis, because it gives not only high surface activity but also various biological activities. In this study, the linear form of surfactin was synthesized by the hydrolytic cleavage of general surfatin, and the effect of peptide structure on the self-assembly and aqueous phase behavior was investigated by surface tension measurement, the fluorescence-probe method, freeze-fracture transmission electron microscopy (FF-TEM), circular dichroism (CD) spectroscopy, and small angle X-ray scattering (SAXS). Our results clearly demonstrated that the cyclic structure of surfactin plays a critical role in their distinctive self-assembling properties

4. Directed assembly of colloidal crystals by photoinduced thermophoresis

Youngri Kim1 youngri@umich.edu

, Aayush A Shah2, Michael J Solomon1,2. (1) Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109, United States (2) Department of Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI 48109, United States

Methods for reversible assembly of colloids are useful for the fabrication of advanced functional materials and devices. Here we demonstrate assembly of colloids by exploiting photoinduced thermophoresis. Self-assembly of particles into dense crystals is directed by the application of visible or UV light in the vicinity of an indium tin oxide (ITO) coated surface. The assembled colloidal crystals are 3D structures, with crystalline order extending out 10 microns from the surface. We use confocal microscopy to characterize the assembly kinetics and the density of the 3D crystal. We hypothesize that the ITO coating absorbs radiation, thereby generating a flux of heat into the suspension. This heat flux induces a thermal gradient within the solution that drives thermophoretic particle motion. We model the heat flux to estimate temperature gradient profiles, compute theoretical thermophoretic particle velocities, and compare these results to direct measurements of the colloid mobility during the assembly.

5. Magnetic assembly and patterning of general nanoscale materials through nonmagnetic templates

Le He lhe001@ucr.edu

Yadong Yin. Department of Chemistry, University of California, Riverside, Riverside, CA 92507, United States

Applied magnetic field represents an effective tool to rapidly assemble micro- and nanoscale magnetic objects into defined structures. Ordered assembly is typically achieved by using magnetic micro-patterns, for which the downside is that they require advanced microfabrication techniques to produce. Herein we present a general strategy that allows convenient magnetically-driven assembly of nonmagnetic objects in defined locations with high spatial resolution. The process involves immersing a polymer relief pattern in a uniformly magnetized ferrofluid, which modulates the local magnetic fields around the pattern. Nonmagnetic target objects dispersed in the same ferrofluid can then be magnetically assembled at positions defined by the polymer pattern. Our method provides a general yet very effective means to assemble a wide range of nonmagnetic objects with controlled spatial distribution, paving the way towards patterning functional microstructures.

6. Directed co-assembly of heteroaggregating particles into permanent chains of tunable length

Bhuvnesh Bharti1 bbharti@ncsu.edu

Gerhard H. Findenegg2, Orlin D. Velev1. (1) Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27606, United States (2) Stranski Laboratorium, Institut für Chemie, Technische Universität, Berlin, Berlin 10623, Germany

Assembling colloidal particles permanently presents a challenging research topic. Dielectrophoresis (DEP) is a widely used method for assembling charged colloids. However, the DEP induced structures formed by similarly charged particles are temporary and last only as long as the field is present. Here we will report a new class of permanently field-assembled structures from binary mixtures of microspheres of opposite charge with strongly attractive interactions. In the absence of any external directing force, oppositely charged particles form random aggregates. We use DEP as a tool to direct the heteroaggregation of biparticle dispersion and the length of permanent chains depend on the size ratio as well as the number ratio of the two interacting species. By our experiments and the corresponding analysis with a unique combinatorial approach, we derived the assembly rules for the resulting structures (Bharti et al., Sci. Rep., 2012 , 2, 1004).

7. Characterization of Dissolved Organic Matter in Petroleum Process Affected Waters

S. Bhattacharjee

Petroleum extraction involves bringing large volumes of water in close contact with hydrocarbons. Many non-conventional petroleum extraction processes, such as steam flooding (SF) and steam assisted gravity drainage (SAGD) employ high temperatures and pressures, that result in solubilization of a multitude of petroleum hydrocarbons into the process affected water. The goal of this presentation is to describe our ongoing work on identification and characterization of the wastewater stream from some of these upstream petroleum extraction plants. Ion-exchange, membrane, and liquid chromatographic fractionation were used to classify the dissolved organic matter in these waters. Following this, each fraction was characterized using bulk spectroscopic techniques, electrospray ionization mass spectrometry, and peptide array libraries. Collectively, these studies provide considerable insight regarding the aggregation behavior and mobility of these molecules and their aggregates in natural environments.

8. Enhancement of ion transport rates in desalination of brackish water by capacitive deionization

Sotira Yiacoumi1 sotira.yiacoumi@ce.gatech.edu

Ketki Sharma1, Richard Mayes2, Jim Kiggans2, David DePaoli2, Sheng Dai2, Costas Tsouris2. (1) Department of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332, United States (2) Oak Ridge National Laboratory, United States

Desalination of brackish water via capacitive deionization (CDI) is based on the electrosorption of ions by charged electrodes of high surface area. Mesoporous carbon electrodes of 10-nm average pore size were synthesized at Oak Ridge National Laboratory (ORNL). We have investigated the influence of temperature and the effect of application of a low-amplitude, high-frequency, alternating-current (AC) electrical signal on ion transport rates in carbon electrodes. Higher rates of sorption and regeneration were observed when an AC signal was superimposed on a direct current (DC) offset of 1.2 V. Neutron imaging was also employed to quantify the diffusion of ions through mesoporous carbon electrodes during electrosorption. Sequences of neutron images showed enhanced transport of neutron-absorbing ions under the influence of an AC signal. It was found that the rates of ion sorption and release by the carbon electrodes also increase with an increase in the temperature of the solution.

9. Novel antifouling reverse osmosis membranes grafted with biocidal silver nanoparticles and antifouling polymer brushes

Saifur Rahaman1 saifur.rahaman@concordia.ca

Heloise Therien-Aubin2, Christopher Kemper Ober3, Moshe Ben-Sasson4, Menachem Elimelech4. (1) Department of Building, Civil and Environmental Engineering, Concordia University, Montreal, Quebec H3G 1M8, Canada (2) Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada (3) Department of Materials Science and Engineering, Cornell University, Ithaca, NY 14853, United States (4) Department of Chemical and Environmental Engineering, Yale University, New Haven, CT 06511, United States

In order to control the bio-fouling of thin-film composite polyamide reverse osmosis membranes, we have developed novel surface coatings via polyelectrolyte layer-by-layer (LBL) self-assembly, functionalized with biocidal nanoparticles and antifouling polymer brushes. The coatings are prepared with polyelectrolyte [PEI: poly(ethylene imine); PAA: poly(acrylic acid) (PEI/PAA)] LBL films containing PEI coated silver nanoparticles (Ag-PEI), grafted either with hydrophilic [poly(sulfobetaine)] or with low surface energy [poly(dimethylsiloxane), PDMS] polymer brushes. Overall, surface modifications resulted in significant reduction of bacterial cell adhesion without affecting the membrane permeability. In static bacterial adhesion tests with E. coli K12 MG1655, a normalized cell adhesion in the range of only 4 to16% on the modified membrane surfaces is observed. Modified surfaces containing silver nanoparticles are also noted to have strong antimicrobial activity. The membranes containing bilayers of PAA/100% Ag-PEI are observed to achieve over 95% inactivation of bacteria attached to the surface within 1 hour of contact time.

10. Investigations of microbial adhesion to advanced water treatment membrane materials

Teresa L Kirschling teresa.kirschling@nist.gov

Jason P Killgore. Division of Applied Chemicals and Materials, National Institute of Standards and Technology, Boulder, Colorado 80305, United States

Membrane based water purification will be essential for providing potable water from saltwater and wastewater as global water scarcity becomes more pressing. One of the biggest challenges to membrane based water treatment processes is biofouling which causes significant increases in transmembrane pressure drop and decreases in flux. Advanced membrane materials have the potential to decrease biofouling, but systematic studies of microbial adhesion to these new materials have not been performed. The bacterial community structure from a reverse osmosis pilot plant was examined by tagged pyrosequencing of the 16S rDNA gene. The sequencing data was compared to a suite of isolates from the membranes. Atomic force micrcoscopy and the quartz crystal microbalance were used to study the adhesive properties of the isolates. Ultimately these results will aid in the development of biological force microscopy tools for rapidly screening advanced membrane materials.

11. Functionalized carbon nanotubes as a source and precursor for disinfection byproducts

David M Cwiertny1 david-cwiertny@uiowa.edu

Edgard M. Verdugo1, Kelly Genskow2, Ying Han3, Caitlin Krause1, Timothy E. Mattes1, Richard L. Valentine1. (1) Civil and Environmental Engineering, University of Iowa, Iowa City, IA 52242, United States (2) Department of Chemistry, University of Wisconsin, Oshkosh, Oshkosh, WI, United States (3) Harbin Institute of Technology, China

The extensive production and application of carbon nanotubes makes their release into the natural environment, including drinking water sources, inevitable. Here, we consider the role that functionalized carbon nanotubes (CNTs) play in the formation of disinfection byproducts (DBPs) via reaction with chlorine-based disinfectants during simulated water treatment. Notably, we find that aminated CNTs are not only a precursor but also a source of nitrogenous DBPs including N-nitrosodimethylamine (NDMA). Several forms of commercially available aminated CNTs were found to leach NDMA into solution upon dispersion of their dry powders. Further, reaction of these aminated CNTs with hypochlorous acid (HOCl) yields NDMA. Evidence suggests reaction with HOCl also results in a modest degree of chlorine addition to the aminated CNT surface. The implications for such CNT surface modification on both their solution phase stability and toxicity are also addressed.

12. Nanoparticles At Water-Oil Interfaces: From Fundamentals to Pickering Emulsions

Alberto Striolo astriolo@ou.edu

Cuong X. Luu, Jing Yu. School of Chemical, Biological and Materials Engineering, The University of Oklahoma, Norman, OK 73019, United States

The stability of Pickering emulsions is related to structural and dynamical properties of interfacial nanoparticles. Such properties are investigated here by means of DPD simulations. Several nanoparticles are considered, including spherical and elliptical, Janus or homogeneous with different amounts of hydrophilic/hydrophobic surface groups. We focus on (a) the effect of particle properties on self-assembled aggregates structure, and (b) systems of different composition. For example, systems containing both homogeneous and Janus nanoparticles are investigated. For a given composition, simulations are conducted at increasing nanoparticle density. The results are quantified in terms of radial distribution function, hexagonal order parameter, contact angle, and self-diffusion coefficient. At high surface density 'caging' phenomena are observed, where the diffusion of a nanoparticle is hindered by the rigid structure (i.e., cage) formed by surrounding nanoparticles. Cage relaxation and rearrangement are discussed. Implications of such observations on macroscopic observables are discussed.

13. Amphiphilic Janus cylinders at fluid-fluid interfaces

Daeyeon Lee1 daeyeon@seas.upenn.edu

Bum Jun Park1,3, Chang-Hyung Choi2, Sung-Min Kang2, Kwadwo E. Tettey1, Chang-Soo Lee2. (1) Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States (2) Department of Chemical Engineering, Chungnam National University, Republic of Korea (3) Department of Chemical Engineering, Kyung Hee University, Republic of Korea

We study the behavior of amphiphilic Janus cylinders at fluid-fluid interfaces using experimental and theoretical approaches. We observe that high aspect ratio Janus cylinders have two configurations – upright and tilted orientation, whereas Janus cylinders with small aspect ratios adopt only the upright orientation. These configurations are confirmed by numerically calculating and minimizing the attachment energy of each Janus cylinder as a function of the orientation angle and vertical displacement with respect to the interface. Unlike homogenous cylinders which show deterministic assembly behaviours at fluid interfaces, Janus cylinders exhibit a variety of assembly behaviours. We show the origin of such a diversity stems from the attractive capillary interactions between tilted Janus cylinders, which could be explained by the complex interface deformation around each particle. We will also describe our recent results involving the configuration and interactions of asymmetrically hydrophilic cylinders at an air-water interface.

14. Dumbbell particles as a model for colloidal surfactants

Sijia Wang siwang@mines.edu

Fuduo Ma, Ning Wu. Chemical and Biological Engineering, Colorado School of Mines, Golden, Colorado 80401, United States p>

There is an arising interest to study Janus particles as colloidal surfactant because of their high emulsion stability and the amphiphilic properties which mimic molecular surfactants. Compared with spherical Janus particles which studied widely, we found that colloidal dimers show even more rich interfacial behaviors. Two types of dimers (surface anisotropic and bulk anisotropic), both showed adsorption at the oil-water interface through different time. The effects of the aspect ratio and degree of fusion between two lobes on interfacial behaviors were also being investigated. Besides, we also studied the interfacial behaviors of polystyrene-poly(N-isopropylacrylamide) dimers. Since pNiPAM lobe is hydrophilic below LCST and hydrophobic above LCST (its size shrinks during this transition), we created a temperature sensitive colloidal surfactant that changes both geometry and hydrophilicity. By incorporating other polymers, such as poly(acrylic acid), pH-sensitive dimers can be achieved, too. On-demand stabilization or destabilization of the emulsions was also conveniently achieved.

15. Reversible assembly of ion-pair nanoparticles at the oil-water interface

Joelle Frechette jfrechette@jhu.edu

Xiaoqing Hua, Mingxiang Luo, Michael A Bevan. Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland 21218, United States

The driving force for the adsorption of small nanoparticles (5 - 10 nm) at the oil-water interface can be small and is particularly sensitive to the surface chemistry of the particles. We will discuss the reversible interfacial assembly of 5 and 10 nm diameter gold nanoparticles functionalized with stoichiometric ion-pairs.[1] Using titration we will demonstrate that the mechanism for particle desorption from the interface is the electrostatic repulsion between the nanoparticles due to pH-dependent adsorption of hydroxide ions. By controlling electrostatic repulsion we can control both the extent of adsorption at the interface and the separation between particle within the interfacial film. We will also present a simple model to predict the surface coverage of nanoparticles at the oil-water interface. [1] M. Luo, G. Olivier, and J. Frechette, “Electrostatic interactions to modulate the reflective assembly of nanoparticles at the oil-water interface “, Soft Matter, 8, 11923-11932, 2012.

16. Production of controlled particle-stabilized emulsion droplets using rotary membrane emulsification

Mohamed S Manga(1) pre4msm@leeds.ac.uk

Olivier J Cayre1, Richard A Williams1,2, Simon R Biggs1. (1) Institute of Particle Science and Engineering; School of Process, Environmental and Materials Engineering, University of Leeds, Leeds, West Yorkshire LS2 9JT, United Kingdom (2) College of Engineering and Physical Sciences, University of Birmingham, Birmingham, West Midlands B15 2TT, United Kingdom

There is currently a significant interest in the production of stable emulsions using particulate emulsifiers. In such systems, the key design and manufacturing challenge is the production of emulsion droplets with controlled droplet sizes and low polydispersity. One candidate production technique is membrane emulsification. In this process the oil phase is pushed through a porous membrane into the continuous phase containing a dispersion of the colloidal particles. As the droplets grow from the pores the particles adsorb to the oil-water interface and provide colloidal stability to the newly formed interface. In this study it is illustrated that under optimal conditions highly stable, near monodisperse hexadecane and tricaprylin droplets can be achieved with polystyrene and silica particulate emulsifiers, respectively, using a Rotary Membrane Emulsification technique. The effects of numerous mechanical and chemical properties have been investigated to demonstrate the control over the mean droplet size. x

17. Encapsulation of biological material in colloidosomes

Polly Keen pollyhrk@gmail.com

Alexander Routh, Nigel Slater. Department of Chemical Engineering & Biotechnology, University of Cambridge, Cambridge, Cambridgeshire CB23RA, United Kingdom

A self-assembly technique based on Pickering emulsions can be used to create microcapsules called colloidosomes. This method doesn't require high temperatures or harsh chemicals so can be adopted to encapsulate biological material. Microencapsulation of biological material has many promising applications: protection from harsh external conditions; extension of storage time; ease of separation in bioreactors; or as a carrier / delivery system. Colloidosomes encapsulating viable Baker's yeast and lactic acid bacteria have been created. An aqueous suspension of polymer latex particles plus the biological material was emulsified in a continuous phase of sunflower oil. By adding a small amount of ethanol and salt to the oil phase, the latex particles at the surface of the emulsion droplets aggregate to form the colloidosome shells. The encapsulated microbes were metabolically active and protected from harsh external conditions by transport limitation through the colloidosome shell. The method is currently being adapted to encapsulate enzymes.

18. Physical insights into matrix self assembly and mineralization

Jim De Yoreo james.deyoreo@pnnl.gov

Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, United States

Self-assembly of protein matrices and subsequent mineralization is a widespread paradigm in the biological production of hard materials. To understand the physical controls on these processes, we have applied in situ AFM, dynamic force spectroscopy and molecular dynamics. Our results show that conformational transformations play a key role in controlling the pathways and kinetics of matrix assembly. Moreover, the pathway to the final state often passes through transient, less-ordered conformational states. Thus the concept of a folding funnel with kinetic traps used to describe protein folding is also applicable to matrix self-assembly. Analysis ofmatrix mineralization shows that nucleation is promoted through a reduction in the interfacial energy. However, nucleation via an amorphous precursor is observed at supersaturations that are too low to be explained by classical theory. The existence of pre-nucleation clusters is shown to provide a low-barrier pathway to crystallization that circumvents the large barriers to nucleation.

19. Thermodynamics of calcite nucleation on organic surfaces: Classical vs. non-classical pathways

Michael H Nielsen mhnielsen@lbl.gov

Qiaona Hu2,3, Laura M Hamm4, Jonathan R I Lee5, Udo Becker3, Patricia M Dove4, James J De Yoreo2. (1) Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, CA 94720, United States (2) Molecular Foundry, Lawrence Berkeley National Lab, Berkeley, CA 94720, United States (3) Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109, United States (4) Department of Geosciences, Virginia Tech, Blacksburg, VA 24061, United States (5) Physical Sciences Directorate, Lawrence Livermore National Lab, Livermore, CA 94550, United States

Using self-assembled monolayers (SAMs) as simple models for macromolecular matrices and organic films, we address gaps in our understanding of the reaction dynamics and energetics of nucleation by employing a suite of in situ methods to investigate CaCO3 nucleation. We present measurements of calcite nucleation rates on carboxyl-terminated alkanethiol SAMs that exhibit the supersaturation dependence expected from classical theory, and we describe the reduction in effective interfacial energy and corresponding free energy barrier. The results demonstrate that calcite nucleation on these SAMs is described well in purely classical terms. In addition, we present evidence from SAM-templated calcite nucleation that amorphous particles are not precursors to the crystalline phase. Instead, calcite nucleates independently. These results call into question the emerging view of calcite nucleation as a non-classical process. Finally we show how aspects of templated nucleation can be investigated with in situ transmission electron microscopy at nanometer scale and video rates.

20. Phage-assisted growth and characterization of copper sulfide nanostructures

Mohammed S. Zaman1 mzama002@ucr.edu

Krassimir N. Bozhilov2, Elaine D. Haberer1,3. (1) Department of Electrical Engineering, University of California Riverside, Riverside, California 92521, United States (2) Central Facility for Advanced Microscopy and Microanalysis, University of California Riverside, Riverside, California 92521, United States (3) Materials Science and Engineering Program, University of California Riverside, Riverside, California 92521, United States

The growth of crystalline copper sulfide using a viral template was investigated. Non-specific electrostatic attraction between a genetically-modified M13 bacteriophage and copper cations resulted in both bundles of nanowires and individual, high-aspect-ratio nanowires. Polydisperse nanocrystals 2 to 7 nm in size were located along the length of the viral scaffold. The structure of the copper sulfide material was identified as cubic anti-fluorite type Cu1.8S, space group Fm3 ¯m. Strong interband absorption was observed within the ultraviolet to visible range with an onset near 800 nm. Furthermore, free carrier absorption associated with the localized surface plasmon resonance (LSPR) of the copper sulfide nanocrystals was seen in the near infrared (NIR) with maxima near 1100 nm and 3000 nm. Two terminal I-V measurements were used to characterize the resistance of both bundles of nanowires and individual nanowires.

21. Preparation of calcium hydroxyapatite nanoparticles dispersible in water

Azusa Ozaki1 j7212625@ed.tus.ac.jp

Tsutomu Yoshida2, Toshitaka Yasuda2, Takeshi Endo1, Kenichi Sakai3, Masahiko Abe13, Hideki Sakai13. (1) Dept. of Pure and Applied Chemistry, Tokyo University of Science, Noda, Japan (2) Toyo Suisan Kaisha Ltd., Japan (3) Research Institute of Science and Technology, Tokyo University of Science, Noda, Japan

We report the synthesis of ultra-small HAP particles dispersible in water with the aid of citric acid as a chelation agent. We also studied the effects of various reaction conditions (pH, composition, etc.) on the size and morphology of the HAP particles and discuss the formation mechanism of the well dispersed particles.Calcium hydroxide, citrate acid, and phosphoric acid were added to ultrapure water with various compositions. Then KOH was added to this solution for adjusting pH. The obtained suspension was aged in a water bath at 45C for 48h. Highly dispersive HAP suspensions with bluish-white appearance were obtained at pH 7 in the presence of excess citrate ion. The negatively charged Ca2+/citrate chelate contributes to the formation of well dispersed HAP particles by not only suppressing the crystal growth of HAP particles, but also by adsorbing to the surface of HAP to give enough negative charge.

22. Hierarchical Assembly of Nanostructured LiFePO4

Jianxin Zhu jzhu005@ucr.edu

jzhu005@ucr.edu, Anthony M Lira2, Nichola Kinsinger3, Juchen Guo3, David Kisailus13. (1) Materials Science and Engineering Program, University of California, Riverside, Riverside, California 92521, United States (2) Department of Bioengineering, University of California, Riverside, Riverside, CA 92521, United States (3) Department of Chemical and Environmental Engineering, University of California, Riverside, Riverside, CA 92521, United States

We report a new solvothermal system to synthesize LiFePO4 (LFP) nanostructures as Li-ion cathodes. Here, we modify solution conditions that affect nucleation and growth, yielding nanoparticles with controlled size and morphological features. Crystal phase and growth behavior were monitored by powder X-ray diffraction (XRD), Synchrotron X-ray Diffraction, as well as Transmission Electron Microscopy (TEM), while particles morphologies were investigated via Scanning Electron Microscopy (SEM). Crystal growth mechanisms were interpreted based on time studies of the synthesis process. Initially, vivianite (Fe3(PO4)2•8H2O) formed first due to the sequence of adding precursors. Then this metastable phase evolved into prism-like olivine LiFePO4 nanostructures that appear to assemble via oriented attachment of primary particles. With increasing reaction time, an increased solubility leads to a dissolution-recrystallization process (i.e., Ostwald ripening, OR) resulting in evenly distributed LiFePO4 nanorods. Performance studies showed that the hierarchical assembled structures displayed a superior performance compared to the larger, single crystalline nanorods.

23. Self-assembled nanomaterials for application in energy storage and harvesting

Sarah H. Tolbert tolbert@chem.ucla.edu

Department of Chemistry and Biochemistry, UCLA, Los Angeles, CA 90095-1569, United States

Amphiphilic assembly provides a powerful method to create complex nanoscale architectures through low-cost processing routes. Here we examine ways to use assembly to create materials for energy harvesting and storage. We begin by considering semiconducting polymers with applications in organic photovoltaics. Amphiphilic-assembly can be used to control polymer chain conformation and in turn charge carrier mobility in a system of water-soluble polymers that assemble into cylindrical micelles. When paired with amphiphilic fullerene derivatives, we create water-processable polymer/fullerene colloidal assemblies that show unique photophysics. Novel properties include ultra-fast excited-state electron transfer in solution, solution phase photochromism, and the formation of extremely long-lived charge separated species. If time permits, we will also discuss self-assembled nanoporous materials with applications in energy storage, focusing on high capacity batteries and pseudocapacitors. Block-copolymer templating is used to produce inorganic materials that combine high surface area, open porosity, and mechanical flexibility, all properties that facilitate electrochemical performance.

24. Controlling the Morphology of Self-Assembled Colloidal Pattern by Ion Addition

Satoshi Watanabe nabe@cheme.kyoto-u.ac.jp

Junya Suzuki, Yuichiro Arai, Minoru Miyahara. Department of Chemical Engineering, Kyoto University, Kyoto, Kyoto 615-8510, Japan

Bottom-up self-organization approaches are promising for fabricating higher-order patterned surfaces composed of submicron particles. We have been studying the evaporation-induced self-assembly process of colloidal particles, and reported horizontal stripe, grid, and cluster array pattern formation on a completely hydrophilic substrate. In the present study, we examined the effects of ion concentration on the morphology of resultant particulate films. In a low ion concentration region (~10-5 M), stripes formed vertical to the contact line, which would be due to the fingering instability of the tip of the meniscus. However, under a specific condition, a triangle pattern formed in a high ion concentration region (10-3 M). The requirement for the triangle formation was found out to be the use of a mica substrate and lithium (or sodium) ion. These findings will enable easy control of the colloidal pattern just by adding a small amount of ions.

25. Controlling nanoemulsion rheology using polymer-surfactant self-assembly

Matthew E Helgeson helgeson@engineering.ucsb.edu

Juntae Kim, Yongxiang Gao. Department of Chemical Engineering, UC Santa Barbara, Santa Barbara, CA 93106, United States

We present a new scheme for imparting thermoreversible viscoelasticity to oil-in-water nanoemulsions based on polymer-surfactant self-assembly in solution. Specifically, bridging of polymer-induced micelles in the aqueous phase give rise to a transient network of interdroplet bridges without compromising colloidal stability. Characterization of the structure, dynamics, and rheological properties over a broad range of material chemistries and compositions suggests rules for controlling the resulting viscoelasticity. Remarkably, the linear viscoelasticity of these systems exhibits time-temperature superposition, which is purely driven by dynamics without noticeable structure changes. This allows quantification of an activation energy for network formation, which is correlated with the viscoelastic properties across a number of parameters, including polymer and surfactant concentration as well as droplet size. However, a complex dependence of the activation energy on fluid composition distinguishes these novel viscoelastic nanoemulsions from other types of transient gels, and we reconcile their behavior with established mechanisms of polymer-surfactant complexation.

26. "Raft" formation by block copolymer rod micelles in aqueous solution

Georgios Rizis g4georgios@gmail.com

Theo GM van de Ven12, Adi Eisenberg1,2. (1) Department of Chemistry, McGill University, Montreal, Quebec H3A 2A7, Canada (2) Centre for Self-Assembled Chemical Structures (CSACS), Canada

Block copolymers can yield a wide range of morphologies in selective solvents depending on self-assembly conditions; however, changing the micelle morphology after preparation can be challenging due to slow dynamics of the system, for example, in pure water. This study describes a set of morphological transitions observed in aqueous samples of poly(ethylene oxide)-block-polycaprolactone (PEO-b-PCL), which result in the formation of micron-sized fringed lamellae or “rafts”. The phenomenon is hierarchical and occurs in three steps: spherical micelle formation by the self-assembly of PEO-b-PCL chains in water; association of spheres in one dimension which yields rods; and spontaneous alignment of these rods, which coalesce to form lamellae, in a process analogous to raft formation from logs. Detailed features of this mechanism, including control strategies, are described.

27. Controlling structure and stability of unilamellar vesicles by admixture of amphiphilic copolymers

Michael Gradzielski michael.gradzielski@tu-berlin.de

Katharina Bressel1, Michael1, Jeremie Gumme1,2, Theyencheri Narayanan2. (1) Institut fuer Chemie, Stranski-Laboratorium, Technische Universitaet Berlin, Berlin, Germany (2) ESRF, Grenoble, France

Unilamellar vesicles are interesting self-assembled aggregates that may form spontaneously when mixing cationic or zwitterionic with anionic surfactants. In our experiments the fast formation process was studied by coupling the stopped-flow technique to high-flux SANS/SAXS instruments, allowing to obtain detailed structural information with a time-resolution of 5-50 ms. This was done on a model system composed of perfluorinated anionic and zwitterionic hydrocarbon surfactant, showing that it proceeds via a disk-like intermediate state, yielding very monodisperse unilamellar vesicles. However, these vesicles age rather quickly afterwards. Based on detailed knowledge of the formation process it was possible to manipulate it by admixing amphiphilic copolymers. This leads to larger and very monodisperse vesicles, which now in addition are long-time stable. Accordingly by this shaping approach one can obtain unilamellar vesicles with tunable radii in the range of 20-70 nm and with polydispersity indices of 0.04-0.06, which are attractive for a number of applications.

28. Making Silicon Water Friendly for Biosensing and Biolabelling Applications

J. Justin Gooding justin.gooding@unsw.edu.au

Simone Ciampi, Ying Zhu, Bakul Gupta, Xiaoyu Cheng, Moinul H Choudhury, Bin Guan, Peter J Reece, Katharina Gaus. School of Chemistry and Australian Centre for NanoMedicine, The University of New South Wales, Sydney, NSW 2052, Australia

This presentation focuses on the modification of flat and porous silicon surface via both hydrosilylation of alkenes and alkynes for biophotonic, bioelectrochemical and biomaterials applications. Initially the modification, protection of silicon from oxidation and the characterisation of the organic monolayers will be discussed. The application of flat and porous silicon (PSi) photonic crystals for the capture of mammalian cells followed by monitoring of the release of proteins from these cells will discussed. Then, the synthesis of and applications of silicon quantum dots will be presented. Finally, the modification of flat silicon for applications in electrochemistry using a passivating self-assembled monolayer derived from an alkene will be reported. The modification of silicon electrodes with dialkynes followed by the subsequent modification with redox active species using click chemistry will be discussed. These electrodes are shown to be highly stable and resistant to oxidation and are used in developing switchable surfaces.

29. Development of Novel Analytical Methods Based on Silver Nanoparticles

Danke Xu xudanke@nju.edu.cn

State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China

Silver nanoparticles (AgNPs) have played a significant role in current biotechnology, owing to their unique physical and chemical properties. Recently, several novel electrochemical and optical detection methods based on AgNPs have been developed in our lab in which analytical sensitivity have been further improved. An ultrasensitive EC detection method based on silver aggregate tag and DPV was developed to assay DNA arrays, in which hybridization-induced tags were successfully applied to bind with the DNA target via sandwich hybridization format and offer amplified readout. AgNPs have been applied to a microgap DNA sensor by measuring the changing electrical conductivity. In addition, a stripping approach based on AgNPs has been reported to assay proteins via screen printed electrode (SPE). We report on modified AgNPs with multifunctional oligonucleotides for metal-enhanced ?uorescence(MEF). An ultrasensitive fluorescent detection for protein IgE by combining aptamer that specifically recognizes IgE with the AgNP hybrid probes has been developed.

30. Metal Organic Frameworks as Nitric Oxide Producing Biocatalysts

Melissa M. Reynolds Melissa.Reynolds@ColoState.edu

Jacqueline L. Harding. Department of Chemistry, Colorado State University, United States

The use of nitric oxide (NO)-releasing materials to improve the hemocompatibility of acute medical devices has been well established. Longer term use has been limited by finite storage capacities. In this presentation, a new approach to producing NO will be discussed. Specifically, metal organic frameworks are used as catalysts to facilitate the release NO from S-nitrosothiol (RSNO) substrates. Several structurally diverse RSNOs have been investigated, leading to different kinetic release profiles based upon their structural features. Using this approach the development of MOF materials with tailorable release rates and much longer clinical lifetimes than any other currently available NO biomaterial may provide the requisite NO dosages to lead to long term devices.

31. Evaluation of membrane composition for fabrication of ion channel–functionalized sensors

Maria F Mendoza mfm12@email.arizona.edu

Mark T Agasid, L Kofi Bright, S Scott Saavedra, Craig A Aspinwall. Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States

Ion channel (IC) functionalized sensors provide a new paradigm in label-free, biomimetic sensing of otherwise difficult to detect analytes. IC activation is readily detected via electrophysiology, providing a simple, rapid and label-free approach for assessing analyte/ligand activity in complex samples. Unfortunately, long-term monitoring using IC-functionalized sensors is limited by the inherent instability of natural and artificial lipid bilayers. Identification of membranes with sufficiently low conductance that facilitate reconstitution of functional ICs is of critical importance for realizing IC derived sensing platforms. We have investigated the electrical properties and protein compatibility of black lipid membranes (BLMs) prepared using a range of lipids and cholesterol, as well as binary and ternary mixtures of lipids. Using this approach we observed deviations from ideality in electrical properties that were consistent with the physical/chemical properties of domain formation within the BLM when binary and ternary mixtures were studied compared to BLMs composed of pure lipids.

32. Electrolyte negative differential resistance (NDR) in glass nanopores and its sensing applications

Long Luo long.luo@chem.utah.edu

Henry S White. Chemistry, University of Utah, Salt Lake city, Utah 84108, United States

Negative differential resistance (NDR) is an important electrical phenomenon in which current decreases as the voltage is increased. Various NDR behaviors have been observed in solid-state devices, among which the Esaki or tunnel diode is especially well-known. In this talk, we present a solution-phase chemical analogue of solid-state NDR devices that has potential applications in single-molecule chemical sensing. We produced NDR by placing a higher and a lower concentration KCl solution inside and outside a nanopore, respectively. A steep NDR switch is obtained in the current-voltage curve, indicating a bistability between a high conductivity state and a low conductivity state. The critical potential where conductivity switches and NDR occurs is determined by the surface charge density. Experimental results indicate that the NDR switching potential changes 10 mV in response to a change of ~ 200 surface charges.

33. Conversion of solar into chemical energy on plasmonic metal nanostructures

linic@umich.edu

Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109, United States

We will show that composite photo-catalysts combing plasmonic metallic nanoparticles of noble metals and semiconductor nanostructures exhibit improved photo-chemical activity compared to conventional photo-catalytic materials.1,2 We will also show that plasmonic silver nanoparticles, optically excited with low intensity visible light, exhibit direct photo-catalytic activity. We will discuss underlying mechanisms associated with these phenomena.2,3,4 We propose that this new family of photo-catalysts could prove useful for many heterogeneous catalytic processes that cannot be activated using conventional thermal processes on metals or photo-catalytic processes on semiconductors. I will show an example of such a process.5
1. D. B. Ingram, S. Linic, JACS, 133, 5202, 2011
2. Suljo Linic, Phillip Christopher and David B., Nature Materials, 10 , 911, 2011.
3. Ingram P. Christopher, H. Xin, S. Linic, Nature Chemistry, 3, 467, 2011.
4. P. Christopher, H. Xin, M. Andiappan, S. Linic, Nature Materials , 11, 1044, 2012.
5. Andiappan Marimuthu, Science, accepted for publication .

34. Carbon nanotube membrane supported nanoparticle catalysts for water treatment

Chongzheng Na chongzheng.na@gmail.com

Haitao Wang. University of Notre Dame, Notre Dame, Indiana 46556, United States

The application of nanomaterials in water treatment faces a prohibitive challenge. Because nanomaterials do not settle well, processes employing them run the risk of releasing them in finished water. To provide a viable solution to this challenge, we designed and fabricated 3-D carbon nanotube (CNT) membranes by growing CNT forests on stainless steel mesh supports. We further affixed gold nanoparticles on CNTs and demonstrated the function of the nanocomposite in the catalytic degradation of 4-nitrophenol.

34. Carbon nanotube membrane supported nanoparticle catalysts for water treatment

Chongzheng Na chongzheng.na@gmail.com

Haitao Wang. University of Notre Dame, Notre Dame, Indiana 46556, United States

The surface structures of catalysts have in some instances a large impact on their catalytic properties. On the other hand, historically, mild reactions are not considered to be surface structure sensitive. In this work we report on our observation that both the size and the shape of Pt nanoparticles strongly affect the selectivity of glycerol oxidation, a reaction that can proceed at room temperature and under atmospheric pressures. In a series of experiment using Pt/SiO2 catalysts with average particle sizes varying from 3.9 to 6.2nm, it was determined that selectivity toward primary carbon oxidation increases as the proportion of larger particles increases. Aside from this size effect, supported tetrahedral Pt and cuboctahedral Pt also exhibit different selectivity and kinetic behavior from the regular Pt catalysts. Further characterization of the catalysts and their detailed kinetic behavior is currently under way.

36. Bulk synthesis of catalytic nanomotors - colloidal dimers

Sijia Wang alsophila22@gmail.com

Fuduo Ma, Ning Wu. Chemical and Biological Engineering, Colorado School of Mines, Golden, Colorado 80401, United States

Pt-coated Janus spheres have shown self-propelling behavior in hydrogen peroxide. But they are usually produced by template-assisted method and the geometry of these motors is trivial. By utilizing the surface anisotropy of the two lobes (which can be confirmed by dye and metal NPs attachment), colloidal dimers with only one lobe coated by platinum can be synthesized in large quantities. This type of dimers can show much stronger propulsion than Janus spheres in hydrogen peroxide solutions. Both linear and rotational movements were observed which should due to the position of the bubble generation. Our method offers more opportunities to study the geometry effect, such as the degree of fusion, the size ratio between the two lobes or even trimers with only one lobe having Pt coated, on the propulsion mechanism. We also found other interesting moving behaviors of Pt coated dimers when specific salt was added into the system.

37. Mesoporous oxides supported Pt nanoparticles as a bifunctional catalyst and their catalytic reaction Studies

Kwangjin An akj007@berkeley.edu

Department of Chemistry, University of California at Berkeley, Berkeley, CA 94720-1460, United StatesChemical Sciences and Materials Sciences Divisions, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States

Recent advances of colloidal chemistry provide a novel method to generate both metal nanoparticles and mesoporous materials with controlled structures. There are two different strategies to prepare ordered mesoporous oxides: soft-templating (cooperative assembly) and hard-templating (nanocasting) approaches. Since heterogeneous catalysts are prepared by nanoparticles deposited on oxide supports, oxide-metal interfaces have attracted much attention as an important catalytic site. Herein, mesoporous SiO2, Al2O3, TiO2, Nb2O5, and Ta2O5 were synthesized through a soft-templating approach. The Pt nanoparticles supported on the mesoporous oxides were evaluated in the hydrogenation reaction of furfural to study the effect of catalyst supports on selectivity. Mesoporous oxides of Co3O4, NiO, MnO2, and Fe2O3, were prepared through the nanocasting approach as well. Carbon monoxide (CO) oxidation reactions with different partial pressures of CO and O2 were used to investigate catalytic activity of the mesoporous oxides with and without Pt nanoparticles.

38. Nanomaterials via colloidal assembly for application in energy storage and magnetoelectrics

Sarah H. Tolbert tolbert@chem.ucla.edu

Department of Chemistry and Biochemistry, UCLA, Los Angeles, CA 90095-1569, United States

Colloids can form the foundation for a broad range of nanostructured materials. In this talk we explore two systems produced using solution synthesized nanocrystals. We begin with materials for energy storage, focusing on pseudocapacitors. By producing materials with controlled porosity and high surface area, systems can be optimized for applications requiring a combination of electrical connectivity, electrolyte access to the pore volume, and the presence of surface redox sites. Here, we specifically examine porous pseudocapacitors built from nanocrystal building-blocks. We demonstrate general methods for templating colloids into porous materials and give specific examples in energy storage where this architecture produces fast redox kinetics. We next turn to nanomagnetics, focusing on magnetoelectric systems, which are materials that couple ferroelectricity with magnetism. We find that strain engineering of Ni nanocrystals can be used to create systems where the net magnetization can be turned on and off through application of an electric field.

39. Fabrication of Micelle-Like Nanoreactor for Catalysis

Qiao Zhang (1) qiao.zhang@berkeley.edu

Xingzhong Shu1, Dean Toste1, Gabor A. Somorjai1,2, Paul Alivisatos1,2. (1) Chemistry, University of California, Berkeley, Berkeley, CA 94720, United States (2) Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States

In this presentation, we present the fabrication of micelle-like inorganic structure and its application in organic catalysis. Through a templated approach, metal oxide hollow structure with hydrophilic interior and hydrophobic exterior has been successfully fabricated. Thanks to the unique hydrophilic/hydrophobic interface, the structure has been successfully utilized as a nanoreactor for organic reactions and shows superior performance to normal nanoreactor systems.

40. Biomimetic synthesis of platinum multiple-twinned nanowire network with high electrocatalytic activity and durability

Lingyan Ruan ruanlingyan@ucla.edu

Enbo Zhu, Zhaoyang Lin, Yu Chen, Yu Huang. Department of Materials Sciences and Engineering, University of California, Los Angeles, CA, United States

Control on the production of 1D nanomaterials as efficient electrocatalysts is highly demanding yet challenging. Here, we report a platinum multiple-twinned nanowire network (Pt MTNN) structure synthesized through biomimetic control with specific peptides. The PtMTNN possesses diameters as thin as ~ 2 nm, and polycrystalline structures with segments connected by twin planes. Mechanistic investigation revealed that the PtMTNN forms by attachments of quasispherical particles mediated by peptides. The presence of twin planes and grain boundaries in PtMTNN allowed for increased activity (more than 2 times higher) for methanol oxidation reaction compared to commercial Pt/C catalyst. The PtMTNN also showed a higher electrochemical surface area (ECSA) (80.75 m2/g), and enhanced specific activity (0.139 mA/cm2) and mass activity (0.112 mA/ug) in oxygen reduction reaction. In addition, the PtMTNN showed improved electrochemical durability under repeated cyclic voltammetry scans.

41. Monodisperse PtCu@Cu Nanocrystals and Their Conversion to Hollow-PtCu Nanostructures for Methanol Oxidation

Xiaoqing Huang hxq006@gmail.com

Department of Material Science and Engineering, UCLA, Los Angeles, California 90095, United States

In this work, we report a facile one-pot strategy to the highly monodisperse and hexagonal shaped bimetallic Pt-Cu nanocrystals having only Cu core coated with PtCu alloy (designated as PtCu@Cu nanocrystals). The selective use of FeCl3 is critical to the synthesis of PtCu@Cu nanocrystals. The PtCu@Cu nanocrystals can be deposited on commercial carbon black evenly and the Cu core in the PtCu@Cu was selectively etched. The resulting hollow-PtCu/C is a high-performance electro-catalyst for the methanol oxidation. It has been demon-strated that these hollow-PtCu/C had an high metha-nol oxidation specific activity and mass activity, which are better than those of commercial Pt/C (E-TEK, 20 wt% Pt) catalysts. The hollow-PtCu/C also exhibited better tolerance to the poisoning and more stable than the Pt/C catalyst in the methanol oxidation condition. The results reported herein suggest that superior catalysts can be developed by engineering the structure and composition of the nanocrystals.

42. Orienting Shaped Metal Nanoparticles within Polymer Thin-Film Nanocomposites

Bo Gao bgao@ucsd.edu

Chaitanya Murthy, Yahya Alvi, David Rosen, Gaurav Arya, Andrea Tao. Department of Nanoengineering, University of California, San Diego, La Jolla, CA 92093, United States

In the fabrication of nanocomposites, the controlled organization of nanoparticles (NPs) into hierarchically ordered structures plays a critical role in materials function. We demonstrate that polymer-grafted colloidal metal NPs undergo spontaneous self-assembly within a polymer matrix. Phase separation of NPs into string-like superstructures enables the formation of nanojunctions between neighboring NPs. Inter-NP orientations within these nanojunctions are well-defined and can be tuned through parameters such as NP shape and grafted polymer chain length. We further explore the kinetics of NP assembly within polymer phases by monitoring the evolution of these dynamic NP superstructures during the assembly process.

43. Self-propelling particles programmed to 'dance' and collect oil on water

Rachita Sharma rsharma3@ncsu.edu

Lisa D'Costa1, Suk Tai Chang2, Orlin D. Velev1. (1) Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695-7905, United States (2) School of Chemical Engineering and Materials Science, Chung-Ang University, Seoul, Republic of Korea

We will present gel-based particles that are composed of an ethanol infused hydrogel, and exhibit a remarkable pulsating motion in water over long duration [1]. The asymmetric release of ethanol generates a cycle of Marangoni-effect driven flows followed by interruption of the ethanol transport to the air-water interface, resulting in periodic propulsion of the particle. We have modeled the pulse interval and distance propelled by these gel-boats, and demonstrated that they can be programmed to move in complex trajectories. We will also present a new method for simultaneous disruption and collection of oil films on water using such autonomously propelling particles. These particles may find applications for cleaning up oil spills in environmental remediation. This work is an initial step in the design of prototypes of devices capable of performing complex functions such as drug delivery, sensing. [1] R. Sharma, S. T. Chang, O. D. Velev, Langmuir, 28, 10128-10135 (2012)

44. Experimental and Sensitivity Analysis on the Mobility of Aluminium Oxide Nanoparticles in Saturated Sand

Heather J Shipley heather.shipley@utsa.edu

Tanzina Rahman. Civil and Environmental Engineering, University of Texas at San Antonio, San Antonio, TX 78249, United States

The need to develop a deeper understanding of the nature, fate and behavior of nanoparticles in the environment is driven by the increased use of engineered nanoparticles in consumer products. In this study, the mobility of two sizes of aluminium oxide nanoparticles in saturated sand was investigated under different experimental conditions. The filtration of these particles showed significant dependence on several factors such as ionic strength (0-100mM), flow rate (849-2546µL/min), nanoparticle concentration (50-400 mg/L), nanoparticle size, aggregation tendency, solution pH and the method of preparation of the nanoparticles. Diffusion was found to be the predominant mechanism for nanoparticle contact with the sand surface. The ~200nm particles were less mobile likely due to straining whereas the ~80nm particles underwent blocking. The use of sensitivity analysis on modelled experimental results and the single collector contact efficiency equation will also be discussed to determine the relative importance of specific parameters.

45. Effects of natural organic matter, surface water, and ground water on the fate and transport of graphene oxide nanoparticles in saturated porous media

Jacob D Lanphere jlanp001@ucr.edu

Sharon L Walker, Corey Luth, Brandon Rogers. Department of Chemical and Environmental Engineering, University of California, Riverside, Riverside, California 92521, United States

We characterized the mobility and deposition of selected precious metal nanoparticles (e.g. silver) on various types of of surfaces (such as silica) over a wide range of pH and ionic strength conditions, including seawater and freshwater. In general, the nanoparticles were found to be highly mobile under these conditions with little or no deposition.

46. Mobility of precious metal nanoparticles in the environment

Beng Joo Reginald Thio1 reginaldthio@sutd.edu.sg

Mahmoud A Mahmoud3, Arturo A Keller2. (1) Engineering Product Development, Singapore University of Technology and Design, Singapore (2) Bren School of Environmental Science and Management, University of California, Santa Barbara, United States (3) Department of Chemistry and Biochemistry, Georgia Institute of Technology, United States

Recently widespread studies of graphene oxide have been growing due to its potential application in electrochemical devices. However, to date there is little known regarding the behavior of these particles once released into aquatic environments. Therefore, an in depth study regarding the stability and transport of graphene oxide nanoparticles (GONPs) under conditions simulating different aqueous environments was conducted in saturated porous media. The electrokinetic properties and hydrodynamic diameters of GONPs as a function of natural organic matter (NOM) presence and water sources (surface and ground) were determined. Results suggest NOM and water sources affect the stability of GONPs at higher ionic strength (IS) conditions. Finally, the transport study was performed through a packed bed column and preliminary results from breakthrough curves and column dissections suggest that GONP transport is decreased at higher IS and in the presence of Mg+2 and Ca+2 ions which are ubiquitous in ground and surface waters.

47. Carbon nanoparticles mobilize hydrophobic organic contaminants in groundwater: Linking aggregation properties and contaminant-mobilizing capabilities

Wei Chen chenwei@nankai.edu.cn

John Fortner2, Mason Tomson3. (1) College of Environmental Science and Engineering, Nankai University, China (2) Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, United States (3) Department of Civil and Environmental Engineering, Rice University, United States

We found that carbon nanoparticles (e.g., nC60) in aquatic environments can significantly mobilize hydrophobic organic contaminants by serving as a contaminant carrier. The capability of carbon nanoparticles to enhance contaminant transport is far greater than that of natural colloids (e.g., dissolved organic matter), and likely attributable to the unique porous structures of carbon nanoparticles that result in both enhanced adsorption affinity and desorption irreversibility of contaminants. Interestingly, different nC60 samples prepared with different methods (e.g., solvent exchange from toluene or tetrahydrofuran; long-term stirring or sonication; alternating detailed aggregation formation processes by involving a secondary solvent; etc.) exhibit vastly different contaminant-mobilizing capabilities, likely due to the differences in aggregation properties (e.g., pore volume and pore geometry) among the samples, as controlled by the specific water chemistry and detailed aggregation formation routes. The unique morphology-dependent contaminant-mobilizing capability should be fully understood for the risk assessment of engineered carbonaceous nanomaterials.

48. Clogging by colloid deposits: Fluid velocity, ionic strength, and fractal dimension

Eric J Roth eric.roth@ucdenver.edu

David C Mays. Department of Civil Engineering, University of Colorado Denver, Denver, Colorado 80204, United States

Environmental aspects of colloids are a major research area, particularly with regard to contaminant transport. In contrast, less attention has been given to clogging by colloid deposits, which is important for granular media filtration, aquifer storage/recovery, and groundwater remediation. Evidence suggests that clogging correlates with colloid deposit morphology, which can be quantified as a fractal dimension. Using static light scattering measurements in a flow column of index matched porous media, deposit fractal dimension can be quantified. This presentation will report how clogging and deposit fractal dimension correlate with flow velocity and ionic strength, supporting the broader goal of developing a model linking permeability to colloidal and environmental characteristics.

48. Clogging by colloid deposits: Fluid velocity, ionic strength, and fractal dimension

Eric J Roth eric.roth@ucdenver.edu

David C Mays. Department of Civil Engineering, University of Colorado Denver, Denver, Colorado 80204, United States

Environmental aspects of colloids are a major research area, particularly with regard to contaminant transport. In contrast, less attention has been given to clogging by colloid deposits, which is important for granular media filtration, aquifer storage/recovery, and groundwater remediation. Evidence suggests that clogging correlates with colloid deposit morphology, which can be quantified as a fractal dimension. Using static light scattering measurements in a flow column of index matched porous media, deposit fractal dimension can be quantified. This presentation will report how clogging and deposit fractal dimension correlate with flow velocity and ionic strength, supporting the broader goal of developing a model linking permeability to colloidal and environmental characteristics.

49. Nanofluidics: Wetting and spreading phenomena

Darsh Wasan wasan@iit.edu

Alex Nikolov. Chemical and Biological Engineering, Illinois Institute of Technology, Chicago, Illinois 60616, United States

Suspensions of nanometer-sized particles in liquids (nanofluids) are used in a variety of technological applications and biological systems. For example, their spreading and adhesion behavior on solid surfaces can yield materials with desirable structural and optical properties. The wetting and spreading phenomena of nanofluids have been pursued by us both experimentally and theoretically in recent years. This lecture will review the progress made in the wetting and spreading of nanofluids over solid surfaces with an emphasis on the complex interactions between the particles in the nanofluid and with the solid substrate, as well as the spreading of their nanofluidic films containing nanoparticles on hydrophilic surfaces driven by the structural film tension gradient. In addition, this talk will highlight potential applications including cleaning contaminated hard surfaces, and accelerating recovery of hydrocarbon and stimulation of fluids from oil and gas reservoirs.

50. Experimental investigation of dynamic contact angle and capillary rise in tubes with circular and non-circular cross-sectional shapes

Mohammad Heshmati mheshmat@uwyo.edu

Mohammad Piri. Department of Chemical and Petroleum Engineering, University of Wyoming, Laramie, Wyoming 82071, United States

The kinetics of capillary rise in borosilicate glass tubes of different sizes and cross sectional shapes were studied using various fluid systems. We focused on the direct measurement of dynamic contact angle and its impact on rise. We investigated this relationship for a wide range of invading fluid density and viscosity. For circular tubes, the measured dynamic contact angles were used with the Washburn equation resulting in a significantly-improved agreement with the experimentally-measured rise vs. time data. We show that this approach is effective in other cases as well, e.g., when tubes are tilted 45 degrees. We also present measurements of rise in non-circular capillary tubes where rapid advancement of arc menisci in the coroners ahead of main terminal meniscus impacts the dynamics rise. Using an extensive set of the experimental values, an empirical correlation is presented to obtain dynamic contact angle values during rise experiments for circular capillary tubes.

51. New method of phospholipid bilayer deposition on soft polymer supports using bicelles

Qasim Saleem qasim.saleem@utoronto.ca

Amy Petretic1, Peter M Macdonald12. (1) Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada (2) Department of Chemistry, University of Toronto, Toronto, ON M5S 3H6, Canada

Lipid bilayer deposition on soft polymer spheres or planar cushions is used to form drug delivery vehicles, biosensors, or substrates for biophysical studies. With a view towards developing a method for spontaneous bilayer formation, we have coated anionic poly(N-isopropylacrylamide) (pNIPAM) / p(NIPAM-co-acrylic acid) core / shell microgels with lipid bilayers introduced in the form of cationic discoidal bicelles composed of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), 1,2-dimyristoyl-3-trimethylammonium-propane (DMTAP) and 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC), at ([DMPC]+[DMTAP])/[DHPC] = 2. Coulombic attraction between the anionic microgel and the cationic bicelles produced deposition of an intact continuous lipid bilayer completely coating the microgel surface, as demonstrated via FRAP, 31P NMR and ESI MS. In contradistinction to the dehydration, freeze-thaw or divalent cation treatments needed to induce unilamellar lipid vesicles to form single bilayers on soft surfaces, bicelles spontaneously assemble into single lipid bilayers when deposited on such supports.

52. Wettability Characterization of Living Cell Layers Through Aqueous Biphasic Systems-Mediated Contact Angle Measurements

Hossein Tavana1 qasim.saleem@utoronto.ca

Golnaz Jalalahmadi2, Ehsan Atefi1, Robert Mallik2, tavana@uakron.edu. (1) Biomedical Engineering, The University of Akron, Akron, Ohio 44, United States (2) Physics, The University of Akron, Akron, Ohio 44325, United States

Surface wettability of living mammalian cells is important for many physiological processes including adhesion of bacterial and cancer cells to tissue surfaces. We employ contact angle measurements with polymeric aqueous two-phase systems (ATPS) to characterize wettability of cell layers. Living cells grown to a confluent monolayer are immersed in the lighter aqueous phase. A drop of the denser phase is dispensed to form a sessile drop on cells. The asymmetry of the drop due to roughness of the cells layer and the lack of reflection of the drop on the surface hinders using conventional drop shape methods to determine contact angles from the drop image. Thus, we develop a numerical module that employs a series of image processing techniques to extract the drop profile, fit polynomials, and apply statistical criteria to resolve contact angles. We demonstrate the utility of this approach to determine contact angles on cell monolayers.

53. Surfactant imprinting of the surface of silica nanoparticles for selective adsorption of sugars with subtle structural differences

Suvid Joshi suvid.joshi@uky.edu

Barbara Knutson, Stephen E Rankin. Department of Chemical and Materials Engineering, University of Kentucky, Lexington, KY 40506, United States

Separation of targeted saccharides in the bioprocess industry is a significant unmet challenge; previously reports have focused primarily on separating sugars differing in numbers of carbon atoms. Here we demonstrate that simply imprinting the surface of freshly precipitated silica nanoparticles using sugar-based surfactants yields materials that selectively adsorb saccharides based on subtle structural differences. Imprinted Stöber silica particles are prepared by adding surfactants just after precipitation, when they have reached their final shape but remain soft. Selective imprinting for D-glucose using octyl-ß-D-glucopyranoside mixed with hexadecyltrimethylammonium bromide is optimized and tested using a series of hexose sugars. Selective adsorption of D-glucose vs. L-glucose is shown, as well as the effects of changing the chirality of individual carbons (e.g. galactose vs. glucose). The ability to resolve disaccharides differing in their type of linkage will be shown by imprinting particles with dodecyl-b-D-maltoside to give selectivity for maltose vs. cellobiose adsorption.

54. Mimicking biomineralization using colloidal assembly

Laurie B. Gower lgowe@mse.ufl.edu

Materials Science & Engineering, University of Florida, Gainesville, FL 32611, United States

When considering biomineralization from the perspective of crystal nucleation and growth, one generally doesn't think in terms of colloids. But work in our lab suggests that colloid chemistry is at the foundation of biomineralization, where many of the enigmatic features found in biominerals can be duplicated through the use of a non-classical crystallization process we termed the polymer-induced liquid-precursor (PILP) process. However, recent studies suggest that a liquid phase may already be present in calcium based reaction media; thus, the role of the polymer is to sequester and stabilize this liquid condensed phase such that upon pseudomorphic transformation, it can be molded and shaped into the desired mineral product. Here, I will discuss how this colloidal assembly may be relevant to biominerals, ranging from the formation of CaCO3 biominerals in marine organisms, to the calcium phosphate biominerals in vertebrates, such as bones, teeth, and kidney stones.

55. Phase Transformations and Structural Developments in the Radular Teeth of Cryptochiton Stelleri

Brian Weden bwede001@ucr.edu

Qianqian Wang, Michiko Nemoto, Dongsheng Li, James C. Weaver, John Stegemeier, Krassimir N. Bozhilov, Leslie R. Wood, Garrett W. Milliron, Christopher S. Kim, Elaine DiMasi, David Kisailus. Bourns College of Engineering, University of California Riverside, Riverside, CA 92521, United States

During mineralization, the hard outer magnetite-containing shell of the radular teeth of Cryptochiton stelleri undergoes four distinct stages of structural and phase transformations: (i) the formation of a crystal- line a-chitin organic matrix that forms the structural framework of the non-mineralized teeth, (ii) the templated synthesis of ferrihydrite crystal aggregates along these organic fibers, (iii) subsequent solid state phase transformation from ferrihydrite to magnetite, and (iv) progressive magnetite crystal growth to form continuous parallel rods within the mature teeth. The underlying a-chitin organic matrix appears to influence magnetite crystal aggregate density and the diameter and curvature of the resulting rods, both of which likely play critical roles in determining the local mechanical properties of the mature radular teeth.

56. Bio-inspired Magnetite Mineralization in Gel Matrix

Baohu Wu1,2 ba.wu@fz-juelich.de

Vitaliy Pipich1, Dietmar Schwahn1, Maria Helminger2, Helmut Coelfen2. (1) Juelich Centre for Neutron Science, Forschungszentrum Juelich, Garching bei Muenchen, BY 85747, Germany (2) Department of Chemistry, University of Konstanz, Konstanz, BW 78457, Germany

Natural living organisms are able to produce highly sophisticated materials at normal conditions. Nacre is an extraordinary example of hierarchical structure. Due to a hierarchical structuring and a well controlled coupling at the interface between the organic-inorganic components, these structures combine both stiffness and toughness. Chiton teeth are another example which extremely wear resistant through a hybrid design of magnetite nanoparticles embedded in a polysaccharide-protein gel matrix. Inspired by these materials design concepts, we aim to develop biomimetic composites which combines the best of the properties of the different biominerals. We synthesized the biomimetic structures that are based on the matrix of nacre as scaffold which is filled with gelatin gel. The magnetite nanoparticles are distributed in the fractal gelatin matrix. Small angle neutron/x-ray scaterring was used to well investigate the magnetite biomineralization mechanisms.

57. Organic templating of zinc oxide with preferred orientation

Wenting Hou houwenting212@gmail.com

Nicholas Stewart, David Kisailus. Department of Chemical and Environmental Engineering, University of California, Riverside, 3429 Florida St., 3429 FLORIDA ST, Riverside, CA 92507, United States

Biological mineralizing processes demonstrate how nature can produce elegant structures through controlled organic-mineral interactions. These organics exist as scaffolds to control shape, size and orientation of mineral. Based on inspiration from Nature, we are using alkane thiol-based self assembled monolayers (SAMs) to serve as templates to guide the growth of ZnO nanostructured materials under mild solution conditions at low temperatures. Here, ZnO nanorods with different crystallographic orientations are obtained on SAM wafers with different chemical functional groups. Other parameters, such as initial reactant concentration, pH, and reaction temperature have also been systematically examined. By understanding the mechanism of ZnO nucleation and growth, through a tuning of the synthetic parameters, we can exert control over nanostructural size, morphology and orientation to affect its performance in optoelectronic devices.

58. Amelogenin-chitosan hydrogel for enamel reconstruction via protein-directed assembly with a dense interface

Qichao Ruan ruanqichao@gmail.com

Janet Moradian-Oldak. Center for Craniofacial Molecular Biology, University of Southern California, Los Angeles, CA 90033, United States

Biomimetic reconstruction of tooth enamel is a significant topic of study in material science and dentistry as a novel approach for prevention and restoration of defective enamel. We developed an amelogenin-containing chitosan hydrogel for enamel reconstruction that works through amelogenin supramolecular assembly, stabilizing Ca-P clusters and guiding their arrangement into linear chains. These amelogenin Ca-P composite chains further fuse with enamel crystals and eventually evolve into enamel-like co-aligned crystals, anchoring to the enamel substrate through a cluster growth process. A dense interface between the newly-grown layer and enamel was formed and the enamel-like layer had improved hardness and elastic modulus compared to etched enamel. We anticipate that chitosan hydrogel will provide effective protection against secondary caries because of its pH-responsive and antimicrobial properties. Our studies introduce amelogenin-containing chitosan hydrogel as a promising biomaterial for enamel repair and demonstrate the potential of applying protein-directed assembly to biomimetic reconstruction of complex biomaterials.

59. Formation of mesostructured polymer-surfactant films at the air-solution interface

Karen J Edler k.edler@bath.ac.uk

Matthew J Wasbrough, James A Holdaway, Robben Jaber. Chemistry Department, University of Bath, Bath, Somerset BA2 7AY, United Kingdom

Solutions of polyelectrolytes with surfactants show a variety of adsorption behaviours at interfaces. We have exploited this phenomenon to create novel solid polyelectrolyte/surfactant films at the air-solution interface, from solutions where the polyelectrolyte is essentially uncharged. In these systems, a self-supporting hydrogel film up to 4 microns thick forms spontaneously at the solution surface. The films contain highly ordered 2D or 3D micellar mesostructures and grow in a few minutes covering the entire interface. Our initial investigations focused on films made from polyethylenimine (PEI) and cetyltrimethylammonium bromide (CTAB) and have been extended to other cationic surfactants with a range of molecular structures, influencing film mesostructure and thickness. This presentation will describe our work on understanding the formation mechanism and properties of these films using grazing incidence diffraction, ellipsometry, Brewster angle microscopy and surface tension measurements. Preliminary studies on their application to dye encapsulation and release will also be reported.

60. Effect of shape anisotropy of janus microparticles on self assembly

Sung-Min Kang sungmin.kang21@gmail.com

Chang-Hyung Choi, Jongmin Kim, Chang-Soo Lee. Department of Chemical Engineering, Chungnam National University, Daejeon, Republic of Korea

Self-assembly at air/liquid and liquid/liquid has been investigated due to its easy manipulation of ordered structures and interparticle interactions. Although, there are many assembly building blocks and techniques have been required including interparticle interaction, solvent properties and particle geometry. It still requires more complex anisotropy in shape to make complex structures. Here, we study self-assembly of patched particles with highly tunable shapes. Patched particles with amphiphilic properties were synthesized by using micromolding. The morphology of the particle is determined by geometry of micromolds. The self-assembly of patched particles were investigated at air/water or air/solvent interface. Capillary force caused by polarity of solvent results in directed assembly of the particles with different number of patches. We expect that the interfacial assembly of patched particles provide a tool for fundamental study such as a particle-particle interaction and hierarchical self-assembly.

61. Interfacial and Solution Self-assembly of Various Surfactant Proteins

Kevin B Vargo kvargo@seas.upenn.edu

Daniel A Hammer. Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA 19103, United States

Nanostructures created through the self-assembly of recombinant surfactant proteins allows for the precise control of surfactant chemistry and simplistic functionalization through molecular biology. We report the formation of self-assembled spherical and worm-like micelles as well as vesicles from various families of recombinantly-produced protein including oleosin and resilin-like-polypeptides (RLP). Protein mutants were characterized through Western blot analysis, MALDI mass spectroscopy, and circular dichroism. Solutions of these proteins self-assemble in various aqueous buffers and structural characterization were completed through cryo-transmission electron microscopy and small angle x-ray scattering. The phase behavior of the proteins was studied by varying the hydrophobic to hydrophilic ratio of the protein blocks. The interfacial properties of the oleosin mutants were studies using long-term Wilhelmy plate experiments and Langmuir trough studies. The use of recombinant techniques to create surfactant proteins allows for compete control over surfactant chemistry and molecular weight, a major advantage over previous polydisperse systems.

62. Magnetic alignment of Co-doped ZnO nanowires in polythiophene films for ordered bulk heterojunction photovoltaics

Candice I. Pelligra candice.pelligra@yale.edu

Pawel W. Majewski, Chinedum O. Osuji. Department of Chemical & Environmental Engineering, Yale University, New Haven, CT 06511, United States

The achievement of ordered arrays of interpenetrating polymer and inorganic nanomaterials remains a challenge in the fabrication of ordered bulk heterojunction (OBHJ) hybrid photovoltaics. Solution-based processing based on directed assembly is a promising and economical means to this end. We demonstrate the achievement of a composite film suitable for OBHJ photovoltaic active layers based on out-of-plane magnetic alignment of Co-doped ZnO nanowires in conjugated polythiophene. Co-doped ZnO nanowires are surface modified with 1-dodecanethiol to allow dispersion in chloroform and added to P3HT:PCBM solution to form organic-inorganic composite blends. Room-temperature paramagnetic properties of the Co-doped nanowires provide a handle for alignment under a 5T magnetic field. Sample rotation during alignment is utilized to effectively break the degeneracy associated with the negative magnetic anisotropy of the nanowires. The desired vertically-oriented configuration is locked in place as the composite film dries under controlled evaporation in the presence of the magnetic field.

63. Arrested chain growth of magnetic particles in a yield stress matrix fluid: Exploiting rheology in colloidal assembly

Jason P Rich1,2 jprich@mit.edu

Gareth H McKinley3, Patrick S Doyle1.1Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, United States (2) Neutron Scattering Sciences Division, Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States (3) Hatsopoulos Microfluids Laboratory, Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, United States

The process of assembling particles into organized functional structures is influenced by the rheological properties of the matrix fluid in which the assembly takes place. Therefore, tuning these properties represents a viable and as yet unexplored approach for controlling particle assembly. This presentation will describe the effect of the yield stress rheology of the matrix fluid on the directed assembly of polarizable particles into linear chains under a uniform external magnetic field. Using particle-level simulations with a simple yield stress model, we find that the balance between the yield stress and inter-particle magnetic forces can lead to arrested chain growth. This behavior is characterized by the relationship between the resulting structural properties and appropriate dimensionless groups. Since field-induced structures can be indefinitely stabilized by the matrix fluid yield stress and “frozen” into place as desired, this approach may facilitate the assembly of more complex and sophisticated structures.

64. Assembly of Spherical Colloids under Electric Field - “New” Results on “Old” Experiment

Fuduo Ma fma@mines.edu

Ning Wu ningwu@mines.edu

Department of Chemical and Biological Engineering, Colorado School of Mines, Golden, Colorado 80401, United States

In the past, the electric-field assembly of spherical colloids with isotropic surface properties has been studied in both two- and three- dimensions. Structures such as FCC, HCP, and BCT crystals have been observed. We recently, however, have observed new types of sphere-packing within a previously unexplored experimental regime: low salt concentrations and low frequency regime. At low particles concentrations, a family of well-defined clusters, ranging from 3 to 10 was observed. At high particles concentrations, the colloidal clusters further assemble and connect themselves into two-dimensional non-close-packed networks. We attribute these new structures to a short-range out-of-plane (the plane refers to the substrate) attraction and a long-range in-plane repulsion. The double layer and in-plane dipolar repulsion make bottom particles in the clusters separated. While the out-of-plane dipolar attraction and particle-substrate attraction could be responsible for the formation of the clusters, i.e., the top central sphere is associated with the bottom spheres.

65. Combining Surface Enzyme Chemistries, Nanostructured Interfaces and Directed Self-Assembly For the On-Chip Synthesis, Capture and Manipulation of Nucleic Acids and Proteins

Robert M. Corn rcorn@uci.edu

Department of Chemistry, University of California-Irvine, Irvine, CA 92697, United States

The multiplexed detection of nucleic acids, proteins and carbohydrates via bioaffinity adsorption onto biopolymer microarrays has become a mainstay tool for biological researchers throughout the world. Increased functionality of these biopolymer microarrays can be achieved by incorporating additional elements in three fundamental areas: novel surface nucleic acid enzyme chemistries, biofunctionalized nanoparticles and plasmonic nanostructured interfaces. In this talk, I will describe several recent examples of the incorporation of these new elements to create enhanced multiplexed biopolymer microarrays: microRNA detection via surface ligation, on-chip synthesis of RNA aptamer microarrays for protein biosensing, on-chip synthesis of protein microarrays from DNA microarrays via coupled in vitro transcription and translation and DNAzyme footprinting for the detection of protein-aptamer complexes on surfaces. I will also briefly discuss the implementation of SPR phase imaging to biopolymer arrays, and the lithographically photo-patterned electrodeposition of gold nanoring arrays for biosensing applications.

66. miRNA detection using alkylated ?-PNAs and ultrabright flurorescent tags in capillary electrophoresis

James W. Schneider1 schneider@cmu.edu

Johnathan M. Goldman1, Bruce A. Armitage2, Danith H. Ly2. (1) Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890, United States (2) Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213-3890, United States

miRNAs are short, noncoding nucleic acids that are biomarkers for a growing number of disease states, including breast cancer, Alzheimer's disease, and heart disease. Because they are only 20-22 bases in length, and are present in trace quantities, they are difficult to detect by conventional PCR and array methods. Here, we present an electrophoretic detection system that uses synthetic ?-substituted peptide nucleic acids, which bind miRNA with great specificity and stability. Low detection limits are achieved using an ultrabright probe in the form of a DNA oligomer saturated with intercalating dye. We will discuss efforts to concentrate miRNA by sample stacking and approaches for multiplexed detection in capillary electrophoresis.

67. Releasing cations from ionic nanocrystals for signal amplification in biosensing

Kenneth Flack wenwan.zhong@ucr.edu

Yang Liu, Jingjing Yao, Wenwan Zhong. Department of Chemistry, University of California - Riverside, Riverside, CA 92521, United States

A sensing strategy has been developed by us that takes advantage of the rapid cation exchange reaction in ionic nanocrystals (NCs) to amplify detection signals, called CXAmp. NCs of CdSe and ZnSe, as well as NC clusters (NCCs) of ZnS have applied for detection of biomarkers. Recently, we have found that using the ZnS NCCs to label and detect the long ssDNA products from rolling circle amplification (RCA) could achieve cascade signal augment. We continue to investigate how surface coating on the NCCs affects the cation exchange rate and have found ways to improve the cation release efficiency and obtain even higher fold of amplification. Moreover, RCA-CXAmp is being applied to detect biomarkers in sera samples using a microchip designed in our group. By employing the unique surface property of the colloidal nanomaterials, CXAmp leads to effective and versatile signal amplification.

68. Calcinated Gold Nanoparticle Films for Surface Enhanced Optical Sensing and Mass Spectrometric Analysis

Chih-Yuan Chen cchen023@ucr.edu

, Sam Hinman, Jicheng Duan, Joseph Kim, Quan Cheng. Department of Chemistry, UC Riverside, Riverside, CA 92521, United States

Gold nanoparticle (AuNP) films are exciting sensing materials due to excellent optical and electronic properties, allowing for cross-platform measurements with surface plasmon resonance (SPR), mass spectrometry, and Raman spectroscopy. We report a novel fabrication method based on layer-by-layer deposition/calcination to generate a thin AuNP layer that is highly stable and reusable. We have utilized SEM and AFM to characterize the nanoscale morphology of the films, and found consistence in thickness and diameter for films created from 5nm and 13nm AuNPs. Complementing these studies were computer simulations utilizing FDTD approach, and the LSPR phenomenon agrees well with experimental spectroscopic data obtained from AuNPs in solution and calcinated AuNP films constructed in silico. The simulation data allow better understanding of the plasmonic resonance coupling and field enhancement that arises from the compact assembly of AuNPs. Optical sensing and MS analysis with AuNP films will be discussed as well.

69. Label free detection of microRNA using p19 protein functionalized carbon nanotubes

Pankaj Ramnani pramn002@ucr.edu

Yingning Gao, Ashok Mulchandani. Department of Chemical and Environmental Engineering, University of California, Riverside, Riverside, California 92521, United States

Small RNA (19-23 nucleotides) molecules play an important role in gene regulation, embryonic differentiation, haematopoiesis, and a variety of cancers. Here, we present a platform for the rapid, sensitive and selective electronic detection of miRNAs using carbon nanotubes field-effect transistor functionalized with Carnation Italian Ringspot Virus p19 protein. miRNA-122a was chosen as the target miRNA, which was first hybridized to a probe molecule. The probe:miRNA duplex was then enriched through binding to the viral protein p19 which selects RNA duplexes of correct length and structure. Control experiments were performed verifying that the dsRNA bind with the p19 protein but not the CNTs and p19 protein only selects duplex RNA hybrids. Finally, the miRNA level was quantified by measuring the change in resistance from the I-V curve. We were able to detect sub-femtomolar levels of miRNAs in the presence of large excess of total RNA at room temperature within one hour.

70. Spectroscopic identification of surface intermediates in the dehydrogenation of ethylamine on Pt(111)

Michael Trenary mtrenary@uic.edu

Iradwikanari Waluyo, Joel D Krooswyk, Jun Yin, Yuan Ren. Department of Chemistry, University of Illinois at Chicago, Chicago, Illinois 60607, United States

Reflection absorption infrared spectroscopy (RAIRS) was used to identify and characterize the surface intermediates formed in the dehydrogenation of ethylamine (CH3CH2NH2) on Pt(111). Ethylamine molecularly adsorbs on Pt(111) at 85 K and remains stable up to 300 K. It partially dehydrogenates upon heating to 330 K to form aminovinylidene (CCHNH2), a stable intermediate with an intact NH2 group and a C-N bond with partial double-bond character. The interpretation of the experimental RAIRS results was aided by density function theory calculations and the use of 15N and D-labeled ethylamine. Upon further heating to 420 K, a second stable surface intermediate is formed that is identified as aminoethynyl, CCNH2. At temperatures above 500 K, HCN is found to be the only desorption product. Both aminovinylidene and aminoethynyl are related to several other stable surface intermediates on Pt(111) containing the C=NH2 moiety that have been previously identified.

71. Catalytic Hydrogenation of Ethylene: Reducing the gap between high pressure and ultra-high vacuum conditions by employing a molecular beam doser

Maryam Ebrahimi ebrahimi@ucr.edu

Francisco Zaera. Department of Chemistry, University of California-Riverside, Riverside, CA 92521, United States

The catalytic hydrogenation of ethylene has been one of the most widely studied reactions in surface science and heterogeneous catalysis. The related molecular-level studies reveal two main regimes: (a) under ultrahigh-vacuum (UHV) conditions, where the reaction involves sub-monolayer coverages of C2H4 and H2 on a clean surface, and cannot be sustained catalytically, and (b) under pressures above the milliTorr range, where the hydrogenation can be sustained catalytically, even if with low probability. We have explored the kinetics of the intermediate regime by employing a home-built molecular beam doser designed for the delivery of high-flux beams of the reactants mixture towards the surface. Our studies have identified the very first steady-state catalytic reaction of C2H4 and H2 on polycrystalline platinum inside a UHV chamber. Almost unit reaction probability has been observed in this intermediate regime. Full characterizations of the kinetic trends associated with the kinetics of the reaction are under way.

72. Chiral propylene oxide adsorption on achiral Pt(111) surfaces.

Stavros Karakalos stavros@ucr.edu

Francisco Zaera. Chemistry Department, University of California Riverside, Riverside, California 92521, United States

For over two decades the search for techniques to obtain enantiomerically pure chemicals has intensified. A number of different approaches have been used to create heterogeneous chiral catalysts, including the adsorption of chiral molecules at solid single-crystal surfaces to induce asymmetry. In this study, temperature programmed desorption (TPD) and molecular beam (MB) experiments have been carried out to investigate how propylene oxide (PO), a small chiral molecule, can bestow chirality to the achiral substrate, a Pt(111) single-crystal surface. TPD results showed that the adsorption of a small initial amount of enantiopure PO on the Pt(111) leads to differences in the coverage of a second probe molecule such as enantiopure propylene oxide or propylene (Py). Sticking probabilities of each probe molecule, calculated from MB experiments on clean Pt(111) and various PO/Pt(111) systems, showed different adsorption kinetics. Initial Monte Carlo simulations have been tried to explain this effect.

73. Imaging a surface explosion: Autocatalytic decomposition of tartaric acid on Cu(110)

Timothy J Lawton1 timothy.lawton@tufts.edu

Bharat Mhatre2, Vladimir Pushkarev2, Brian Holsclaw2, Andrew J Gellman2,3, Charles H Sykes (1). (1) Department of Chemistry, Tufts University, Medford, MA 02155, United States (2) Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, United States (3) US Department of Energy, National Energy Technology Laboratory, Pittsburgh, PA 15236, United States

Autocatalytic reactions occur in many fields and have an initiation event causing the reaction rate to increase non-linearly. These reactions have also been observed on single crystal surfaces (surface explosions) which allowed us to study an autocatalytic decomposition, tartaric acid on Cu(110), with tunneling microscopy and temperature programmed reaction spectroscopy. The initiation results from a small irreversible loss of molecules followed by surface restructuring; Cu adatoms were pulled up from the surface just prior to the onset of decomposition.

74. Photon induced bond activation on nanosized Pt particles

Phillip Christopher christopher@engr.ucr.edu

Matthew J. Kale, Talin Avanesian,University of California, Riverside, Department of Chemical and Environmental Engineering, Riverside, CA, 92507

On cobalt catalysts, the Fischer-Tropsch synthesis proceeds through a carbide mechanism. The first step is the dissociation of carbon monoxide into carbon and oxygen on the surface. Here, colloidal synthesis was used to prepare monodisperse cobalt nanoparticles of 4, 10 and 15 nm diameters. They were exposed to CO and/or dihydrogen. The formation of new surface species and the changes in the surface oxidation state were investigated using in-situ synchrotron techniques. X-ray absorption spectroscopy was performed using a home-built gas cell that operates under 1 bar. The cobalt L-edge and oxygen K-edge revealed a strong dependence of the dissociation kinetics on the nanoparticles diameter. Larger nanoparticles were shown to dissociate CO even at low temperature while smaller ones required heating and exposure to hydrogen. Control experiments showed the role of surface hydrogen store on large particles in this process, clearly demonstrated that CO dissociation is assisted by hydrogen.

75. Towards a molecular level understanding of Fischer-Tropsch synthesis on cobalt nanoparticles

Emily A Lewis1 emily.lewis@tufts.edu

Duy Le2, Talat Rahman2, Charles Sykes1. (1) Department of Chemistry, Tufts University, Medford, MA 02155, United States (2) Department of Physics, University of Central Florida, Orlando, FL 32816, United States

Fischer-Tropsch synthesis (FTS), the conversion of syngas (CO and H2) to fuels, often utilizes Co-based catalysts. We have used low-temperature scanning tunneling microscopy to study the interaction of syngas with Co nanoparticles grown onto Cu(111), an inert metal for FTS. Hydrogen adsorbs dissociatively on the Co nanoparticles, and three coverage-dependent phases are observed. Simultaneous exposure to H2 and CO results in segregated islands of the adsorbates at 80 K. We observe that CO spillover from the Cu surface to the Co nanoparticles causes the buildup of CO at the nanoparticle edges. With increasing CO coverage, two-dimensional compression of H by CO occurs, and after annealing, we see that CO totally displaces H, forcing it to spill over onto the Cu substrate. Using density functional theory, we have calculated the relevant energetics for these processes, and we note that the formation strong CO-Co bonds drives the compression and displacement of H.

76. Polyaniline, graphite oxide, and graphene colloids for device applications

Richard Kaner kaner@chem.ucla.edu

Veronica Strong, Julio D'Arcy, Jonathan Wassei, Jessica Yue Wang, Maher El-Kady, Sergey Dubin, Thomas Farrell, Jaime Torres, Kan Wang, Lisa Wang. Department of Chemistry and Biochemistry and California NanoSystems Institute, UCLA, Los Angeles, CA 90095, United States

The Kaner group has spent the last decade exploring the potential applications of polyaniline, graphite oxide, and graphene colloids. These materials open the door to a wide range of uses in such devices as practical chemical sensors, static dissipative coatings, memory storage, and high-performance supercapacitors. This talk will highlight several of the key findings over our many years of polyaniline- and graphene-related research, including our most recent venture into 3-D graphene architectures. By creating electrically-connected graphene layers with high surface area, light-weight electronics and high energy density storage devices look promising.

77. Critical role of surfactants towards CdS nanoparticles: synthesis, stability, optical and pl emission properties

Surinder Kumar Mehta skmehta@pu.ac.in

Department of Chemistry, Panjab University, Chandigarh, U,T, 160 014, India

Cadmium sulfide (CdS) nanoparticles (NPs) prepared by a convenient chemical precipitation method have been characterized using TEM, XRD, zeta potential, absorption and photoluminescence (PL) emission spectroscopy to establish the critical role of different cationic and anionic surfactants in their stabilization. In the synthesis of CdS NPs, cadmium acetate and sodium sulfide employed as starting reagents were dissolved in aqueous solution of different surfactants to study the effect of their structures on nucleation, growth, optical and PL emission properties of NPs. By varying the surfactant species, CdS NPs having significantly different optical and PL emission properties under similar reaction conditions have been produced. Depending on the surfactant structure, growing CdS NPs have been stabilized by the surfactants to different extents. Surfactant having longest chain length (CTAB), CdS NPs were most stable. Whereas using the surfactant with smaller chain length i.e. in DTAB the NPs were not stable even for one hour.

78. Poly(vinylamine) microgels: pH-responsive particles with high primary amine contents

Brian R Saunders brian.saunders@manchester.ac.uk

School of Materials, University of Manchester, Manchester, England M13 9PL, United Kingdom

pH-Responsive microgels swell when the pH approaches the pKa of the polybase or polyacid chains. We introduce a simple and scalable method for preparation of pH-responsive PVAM microgels. First, non-aqueous dispersion polymerization was used to prepare new monodisperse water-swellable poly(N-vinylformamide-co-2-(N-vinylformamido)ethyl ether microgels (PNVF-xNVEE). Here, x is the mole% of the crosslinker (NVEE) used. Alkali-hydrolysis in water gave colloidally stable poly(vinylamine-co-bis(ethyl vinylamine) ether) (PVAM-xBEVAME) microgel dispersions. The hydrodynamic diameters and electrophoretic mobilities increased as the pH decreased. Soft Matter, 10.1039/c3sm27728c

79. Nanofluids Effect in Thermoresponsive Poly(N-isopropylacrylamide) Microgels

Tatiya Trongsatitkul1,2,3 Bridgette_Budhlall@uml.edu

Bridgette M Budhlall12. (1) Department of Plastics Engineering, University of Massachusetts, Lowell, MA 01854, United States (2) NSF Center for High-Rate Nanomanufacturing, University of Massachusetts, Lowell, MA 01854, United States (3) School of Engineering, Suranaree University of Technology, Najkhon Ratchasima, Thailand

When nanoparticles are incorporated into liquids there is an abnormal increase in thermal conductivity and this is known as the “nanofluids effect”. Herein, this phenomenon was investigated by incorporating various nanoparticles into semi-solid thermoresponsive PNIPAm microgels. Metallic nanoparticles (AuNPs and AgNPs) were compared with a non-metallic nanoparticle (SiO2). Optical microscope studies revealed that the shrinkage of the microgels containing metallic nanoparticles occurred significantly faster than that with nonmetallic nanoparticles and without any nanoparticle. Hybrid PNIPAm microgels containing AuNPs with particle sizes of 10, 20, 40, and 60nm were studied and it was found that the microgels' temperature sensitivity and response kinetics increased linearly with the surface-to-volume ratio of the nanoparticles. The thermal conductivities of PNIPAm microgels were also characterized using modulated-DSC, where we confirmed an increase in temperature sensitivity in the presence of metallic nanoparticles. This is the first study to quantify the thermal conductivities of PNIPAm with incorporated nanoparticles.

80. pH-responsive colloidosomes and their use for controlling release

James Paul Hitchcock james.reality@gmail.com

Olivier J Cayre, Mohamed S Manga, Sam Fincham, Amandine Simoes, Richard A Williams, Simon Biggs. Institute of Particle Science and Engineering, University of Leeds, Leeds, Yorkshire LS2 9JT, United Kingdom

Colloidosome microcapsules have been developed which offer options for the encapsulation and release of active ingredients. We use latex particles, stabilised with a responsive polymer, as building blocks for colloidosome microcapsule membranes and demonstrate their use as a pH-responsive delivery system. Oil-in-water emulsions are prepared and stabilised with latex particles produced by emulsion polymerisation. The core-facing polymer on the surface of the latex particles is chemically cross-linked from the oil phase to produce a robust capsule shell. The pH-responsive polymer on the surface of the constituent particles within the microcapsule membrane can be induced to expand and contract as a function of protonation / deprotanation, thus altering the pore size of the membrane. We show that fluorescently-labelled dextran molecules can be used to demonstrate successful uptake, retention and release from the core.

81. Impacts of Silver Nanoparticles on the Growth and Activity of Model Microorganisms

Claudia K Gunsch1 ckgunsch@duke.edu

Carley A Gwin1, Christina L Arnaout1,2. (1) Department of Civil and Environmental Engineering, Duke University, Durham, NC 27708, United States (2) HDR Engineering Inc., Vienna, VA 22180, United States

The increase of antibiotic resistant microorganisms has necessitated different approaches to wound care; many treatments now rely on silver nanoparticles (AgNPs) because of their unique bactericidal properties. Increased AgNP usage is likely to lead to an increase AgNPs loading into wastewater treatment plants, thus potentially negatively impacting key microorganisms involved in nutrient removal. For this reason, characterization of AgNP toxicity is needed and was undertaken. Three AgNPs with varying coatings (citrate, polyvinylpyrrolidone, gum arabic) were used. The effects were tested on model heterotrophic and bacteria. AgNPs were found to significantly reduce nitrification in Nitrosomonas europaea when total silver concentrations reached 2 ppm or greater. This range also inhibited heterotrophic growth to a lesser extent. In sequencing batch reactors, community analyses show significant community shifts with increasing concentration. Potentially resistant bacterial strains were isolated from the batch reactors. These strains are currently being screened for the identification of potential resistance genes.

82. Chloride concentrations and ionic strength impact the toxicity and stability of silver nanoparticles in bacterial exposure media

Bryant A. Chambers bryantchambers@utexas.edu

Lynn E. Katz, Mary Jo Kirisits. Department of Civil and Environmental Engineering, The University of Texas at Austin, Austin, Texas 78712, United States

Escherichia coli cells were exposed to mercapto-succinic-acid-capped silver nanoparticles or to free silver to evaluate the impact of water chemistry on silver nanoparticle toxicity. The ionic strengths (8.3, 40, and 150 mM) and chloride concentrations (0, 2.68, 31.6, and 140 mM) chosen for the exposure media - in which bacteria were exposed to silver - were chosen to simulate conditions found in growth media, biological buffers, and freshwater. Results show that E. coli is significantly more tolerant to silver nanoparticles as chloride concentration increases and ionic strength decreases. Silver nanoparticle stability was assessed by measuring dissolution rates and surface plasmon resonance. Silver nanoparticles were found to dissolve quickly under conditions with higher ionic strength and higher chloride concentration but had greater stability under conditions with lower ionic strength and higher chloride concentrations. Overall, exposure to silver nanoparticles caused greater toxicity to E. coli as nanoparticle stability decreased.

83. Phenotypic and genotypic responses of Salmonella exposed to groundwater environments: Changes in survival and pathogenicity

Berat Z Haznedaroglu1 berathaz@buffalo.edu

Marylynn V Yates2, Morris F Maduro3, Sharon L Walker4. (1) Department of Civil, Structural, and Environmental Engineering, University at Buffalo, Buffalo, NY 14260, United States (2) Department of Environmental Sciences, University of California-Riverside, Riverside, CA 92521, United States (3) Department of Biology, University of California-Riverside, Riverside, CA 92521, United States (4) Department of Chemical and Environmental Engineering, University of California-Riverside, Riverside, CA 92521, United States

A mutant library of Salmonella were generated and exposed to several groundwater conditions to identify genes required for fitness and survival under these conditions. The mutant library was monitored using a novel screening strategy and analyzed by high-density microarrays. To understand the phenotypic effects of groundwater exposure, S. typhimurium was also exposed to artificial groundwater with residual antibiotics. Representative concentrations of amoxicillin, tetracycline, and a mixture of antibiotics were supplemented to the groundwater. Antibiotic susceptibility analysis and pathogenicity of Salmonella were determined by using human epithelial cells and nematodes weekly. The results showed that the similar set of genes is required for survival among stress conditions tested. Those genes are generally involved in universal stress response regulation, carbon starvation and source depletion, osmotic shock, sugar uptake, and cell division. S. typhimurium remained viable for long periods of exposure to antibiotic supplemented groundwater; however, failed to cultivate as indication of viable-but-nonculturable-state.

84. Fate and transport of three dominate microorganisms in dechlorinating microbial culture KB-1 in porous media under anaerobic conditions

Huixin Zhang huixin2@ualberta.ca

Ania Ulrich, Yang Liu. Department of Civil and Environmental Engineering, University of Alberta, Edmonton, Alberta T6G 2W2, Canada Department of Civil and Environmental Engineering, University of Alberta, Edmonton, Alberta T6G 2W2, Canada Department of Civil and Environmental Engineering, University of Alberta, Edmonton, Alberta T6G 2W2, Canada

Dechlorinating culture KB-1® has been used for groundwater bioaugmentation of sites with inhibitory concentrations of chlorinated ethenes, however, little research has been done to evaluate fate and transport of dominant species in KB-1® under groundwater conditions. In this study, role of solution chemistry on deposition kinetics of two bacteria, Dehalococcoides and Geobacter, and one archaea, Methanomethylovorans in KB-1® were evaluated by analyzing breakthrough curves and retention profiles in packed columns using quantitive polymerase chain reaction. Microbial electrokinetic potentials were measured for testing ionic strengths. Solution chemistry affected microbial electrokinetic potentials and deposition rates greatly. Deposition rates increased with increasing ionic strength. Three species exhibited similar deposition rate coefficients, though Dehalococcides was the least negatively charged species and Methanomethylovorans was the most negatively charged species. Extended Derjaguin-Landau-Verwey-Overbeek model was utilized to evaluate deposition behaviors. Retained microbial profiles showed a spatially constant deposition rate coefficient, in agreement with classic colloid filtration theory.

85. Evaluating the Effects of Outer Membrane Protein (OMP) TolC on the Transport of Escherichia coli within Saturated Sands

Shangping Xu1 xus@uwm.edu

, Lucia Feriancikova1, Sonia Bardy2, Lixia Wang3, Jin Li3. (1) Department of Geosciences, University of Wisconsin Milwaukee, Milwaukee, WI 53211, United States (2) Department of Biological Sciences, University of Wisconsin Milwaukee, Milwaukee, WI 53211, United States (3) Department of Civil Engineering and Mechanics, University of Wisconsin Milwaukee, Milwaukee, WI 53211, United States

We used TolC positive and negative E. coli mutants to evaluate the effects of OMP TolC, a critical component of several antibiotics efflux pumps, on the transport behavior of E. coli within saturated sands. Our results showed that OMP TolC could enhance E. coli mobility. The surface properties of TolC positive and negative E. coli cells were determined and the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, which considers Lifshitz-van der Waals (LW) interaction, the electrostatic double layer (EDL) interaction as well as the Lewis acid-base (AB) interaction between E. coli cells and the surface of quartz sands, were used to explain the observed trend in E. coli mobility. In general, good agreements between the experimental observations and XDLVO calculations were observed. Findings from this research suggested that antibiotic resistant bacteria that express high quantities of TolC could display higher mobility in sandy aquifers.

86. Using shape anisotropy to toughen nanoparticle films and suppress shear band formation

Daeyeon Lee1 daeyeon@seas.upenn.edu

Lei Zhang1, Gang Feng1, Teresa Brugarolas1. (1) Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States (2) Department of Mechanical Engineering, Villanova University, Villanova, PA 19087, United States

We investigate the mechanical behavior of films composed of randomly packed nanoellipsoids with varying aspect ratio using nanoindentation. The packing fraction of nanoellispoids, determined using gravimetric analysis, is found to have excellent agreement with previously reported results based on simulations. Our study shows that the volume fraction of the films rather than the aspect ratio of the particles is the primary factor that determines the modulus and hardness of nanoellipsoid films. We show, however, that the aspect ratio of the nanoellipsoids has a significant impact on the toughness and the failure mechanism of nanoellipsoid films. While short aspect ratio nanoellipsoid films develop shear bands under nanoindentation, films with high aspect ratio nanoellipsoids do not exhibit shear band formation. We will discuss the potential relevance of our results to other types of random packings such as granular materials and bulk metallic glasses.

87. Colloidal nanoparticles designed via radical dispersion polymerization in non-polar solvent: Towards electrophoretic display applications

Alexandre Richez1,2 arichez@illumina.com

Olivier Cayre1, Simon Biggs1, Louise Farrand1, Henry Wilson1, Mark Goulding1. (1) Institute of Particle Science and Engineering, University of Leeds, Leeds, United Kingdom (2) Merck Chemicals Ltd, Southampton, United Kingdom

Radical dispersion polymerizations in non-polar solvents have recently been revisited due to their potential for manufacturing particles for electrophoretic display technologies. Herein, we present our recent progress in applying this technique to design particles of well-controlled properties. We will describe: • The use of polydimethylsiloxane-methacrylate (PDMS-MA) as a stabilizer for dispersion polymerization of methyl methacrylate (MMA) in dodecane as an alternative to traditional poly(hydroxystearic acid)-based stabilizers, • The influence of varying the monomer on the ability to control the size, size distribution and stabilizer grafting density of the MMA latex produced, • A method for introducing a porogen within the PMMA latex particle core to enable the tuning of particle density, • A method for encapsulating pigment particles within the PMMA latex particles, which enables the design of highly reflective inorganic-organic hybrid particles. For this purpose, we will present data obtained from two approaches based on modifying the pigment surface.

88. Vapor-liquid nanoparticle separation in photochemical reactor systems: Design, analysis, and application

Christopher N Bremer cbremer@asu.edu

Nicolas Acuna, Patrick Phelan. School of Engineering Matter, Transport and Energy, Arizona State University, Tempe, AZ 85281, United States

A vapor-liquid phase separation has been implemented in a photochemical reactor to separate the solvent from a colloid solution. The usefulness of the NPTDR system, a system using sunlight without electrical input, is analyzed alongside a benchtop system which utilizes electricity. The optimum nanoparticle concentration has been determined for the NPTDR: The general reaction rates for two substrate types (aqueous and non-soluble substrates) have been obtained, and the industrial applications/limitations of the NPTDR and benchtop systems are further evaluated.

89. Novel nanostructured ceramic/polymer composite coating regulates magnesium degradation

Ian Johnson1 ijohn003@ucr.edu

Khalid Akari1, Huinan Liu1,2. (1) Department of Bioengineering, University of California at Riverside, Riverside, CA 92521, United States (2) Materials Science and Engineering Program, University of California at Riverside, Riverside, Ca 92521, United States

We developed a nanophase hydroxyapatite (nHA)/poly(lactic-co-glycolic acid) (PLGA) composite coating to regulate magnesium (Mg) degradation in revised simulated body fluid (rSBF). The properties and synergy among nHA, PLGA, and Mg make them promising for biodegradable implant applications. The coatings controlled Mg degradation initially (Figure 1), but delamination remains a challenge. In future studies, we will optimize coating processes and characterize the coating's bioactivity.

90. Rational design of hydrophilic and organic matter tolerant polymeric and hybrid polymer-inorganic membranes

Mohtada Sadrzadeh sadrzade@ualberta.ca

Subir Bhattacharjee. Mechanical Engineering, University of Alberta, Edmonton, Alberta T6G 2G8, Canada

Polymeric membranes are easily fouled by organic matter, making them unsuitable for treatment of wastewater containing large amounts of organic matter. Therefore, imparting enhanced hydrophilicity and organic matter tolerance using suitable additives to phase inversion membranes is of significant interest. In this study, we provide two non-dimensional parameters describing the thermodynamic and kinetic effects during formation of phase inversion membranes. These parameters can be evaluated for specific polymeric and inorganic additives, and provide a rational approach for preparation of phase inversion membranes using polymer blends or nanoparticle-polymer blends. Using this approach, the hydrophilicity of a polyethersulfone membrane was enhanced by adding polyethylene glycol and polyvinylpyrrolidone. Furthermore, we use the approach to dope polyethersulfone membranes using indium tin oxide nanoparticles to yield membranes with high electrical conductivity. Through extensive characterization of the membranes, as well as fouling and permeation tests, we demonstrate the extent of performance improvement of the synthesized membranes

91. Interfacial studies of pH-responsive sterically-stabilized latex particles

Olivier J Cayre o.j.cayre@leeds.ac.uk

Mohamed S Manga, Mark D’Souza Mathew, Timothy N Hunter, Simon Biggs. School of Process, Environmental and Materials Engineering, Institute of Particle Science and Engineering, Leeds, United Kingdom

In recent years, several studies have explored the potential to control the ability of particles synthesized from environmentally-responsive polymeric material to adsorb at liquid-liquid interfaces. Some examples have shown the possibility to govern emulsion type and stability, microcapsule porosity and particle diffusion across an interface. In this work, we explore the behavior of sterically-stabilised latex particles at interfaces using a Langmuir trough. Initially, we characterize the behavior of the particles in bulk and relate it to the pH-responsive properties of the polymer shell. Subsequently we investigate the ability of these particles to 1) adsorb at the interface, 2) compress into a monolayer and 3) desorb from the interface. We demonstrate that the 3 phenomena mentioned above are highly dependent upon the solvation of the polymer shell, which drives both the affinity of the particles for the interface and the inter-particle interaction once adsorbed.

92. Tailoring Surface Chemistry for Probing Biomolecular Systems

Regina Ragan rragan@uci.edu

Chemical Engineering and Materials Science, University of California, Irvine, Irvine, CA 92697, United States

Lipid bilayer membranes (LBM), are chemically assembled on metal electrodes as cell membrane mimics. These have applications as biosensors for protein-lipid interactions and protein-protein recognition via a change in electrical or optical response. The mechanical properties and fluidity are of key importance. Atomic force spectroscopy that has pico-Newton force sensitivity is performed to examine how modifying the surface chemistry of vesicles to promote increased vesicle-substrate interactions on Au affects the initiation of LBM formation and resultant mechanical properties.

93. Selective functionalization of large pore mesoporous silica materials capable of protein capturing

Daniel M Schlipf dschlipf@gmail.com

Barbara L Knutson, Stephen E Rankin. Department of Chemical and Materials Engineering, University of Kentucky, Lexington, KY 40506, United States

Advances in mesoporous silica synthesis permit pore size and particle morphology design amenable to protein encapsulation. Identifying protein location (surface or pore -associated) is a major challenge for interpreting the effect of the local environment on protein activity and stability. Another challenge is the selective functionalization of the particle surface to provide favorable interactions or reduce nonspecific binding to silica. This work demonstrates the ability to selectively functionalize the exterior of mesoporous silica materials with pore sizes large enough for protein capture. Mixed surfactant templating and temperature tunable hydrothermal aging are used to obtain the desired pore size. Silane grafting techniques are employed to selectively functionalize the interior pore surface and exterior particle surface with different functional groups. Grafted amino-silanes are fluorescein isothiocyanate tagged and imaged using confocal scanning laser microscopy (CSLM), confirming their location. Protein accessible pore sizes are confirmed by CSLM using Rhodamine B tagged protein loading.

94. Effects of Residual Chlorine on Photocatalytic Performance of a Titanium Dioxide Membrane

Nataly Dakak ndaka001@ucr.edu

Nichola Kinsinger, David Kisailus. Department of Chemical and Environmental Engineering, University of California Riverside, United States

Due to the rapidly growing industry, new chemicals are being discharged into our wastewater system which is causing an emergent concern over public health and safety. Chlorine is effective at oxidizing such compounds and is a strong disinfectant for water-borne disease; however, it frequently forms disinfection byproducts. Photocatalytic degradation of organic compounds is a promising technology for water treatment. Titanium dioxide in an expensive photocatalytic material that effectively mineralizes organics and it is nonhazardous and chemically stable. We have developed a porous, high surface area TiO2 nanoparticle-based membrane with controlled crystallite size, phase, and porosity by varying synthesis and firing conditions. Subsequently, the photocatalytic activities of these membranes are characterized via degradation of an organic dye. The optimal activities of the materials are discussed by the effective surface area, crystal size, and phase. Additionally, the effect of varying concentrations of residual chlorine is characterized to optimize the photocatalyst material.

95. In-vitro spoilation of silicone hydrogel soft contact lenses

Cheng-Chun Peng1 chengchunpeng@berkeley.edu

Neil P Fajardo1, Clayton J Radke1,2. (1) Department of Chemical and Biomolecular Engineering, University of California, Berkeley, Berkeley, CA 94720, United States (2) Vision Science Group, University of California, Berkeley, Berkeley, CA 94720, United States

Fouling of soft contact lenses (SCLs) by lipids and proteins is a major detriment to comfortable wear. To mimic how the eye fouls SCLs, a novel in-vitro blink cell is designed that directly contacts aqueous-insoluble lipid with the lens via tear-film rupture. Artifical lipid (AL) is spread to form a duplex-oil film over artificial tear solution (ATS) covering a SiHy lens. The ATS film between the lens and the lipid layer is periodically ruptured and reformed by withdrawing and re-injecting ATS into the cell mimicking on-eye blinking. As reported in-vivo, we find discrete deposition spots on the lens surface with optical microscopy. 2D lipid and protein composition surface maps using FCLSM and LAESI overlap with the white spots seen by optical microscopy confirming a deposition fouling mechanism.The model blink cell provides a new tool for improving antifouling lens materials, surface coatings, and care solutions without expensive human-subject testing.

96. Three Sisters: Precision Control of Cooling, Evaporation, and Antisolvent Precipitations

Ingo H Leubner ileubner@crystallizationconsulting.com

Research, Crystallization Consulting, Penfield, NY 14526, United States

Isolation and purification of solid reaction products is frequently achieved by three precipitation processes (1) Cooling of a solution, (2) evaporation of solvent, and (3) addition of antisolvents. ('Three Sisters'). These procedures lack theoretical understanding to relate the final crystal population to precipitation procedures, experimental control variables. A model is presented showing that these procedures are related and can be quantitatively controlled. The BNG (balanced nucleation and growth) model (1) provides quantitative information relating the properties of the precipitates to known and controllable variables for each of the 'three sisters'.Main experimental control parameters are the rates of cooling, evaporation, and anti-solvent addition. Knowledge of the temperature dependence of the product-solubility is desirable. The experimental control parameters in combination with the model and observations allow scale-up from research through product development to manufacturing. (1) I. H. Leubner, 'Precision Crystallization', CRC Press, Boca Raton (2009)

97. Liquid crystal self assembly on an amphiphilic bent core Langmuir/Schaefer monolayer

Piotr Popov1 ppopov@kent.edu

Daniel J. Lacks1, Antal Jakli1, Elizabeth K. Mann1. (1) Physics, Kent State University, Kent, Ohio 44242, United States (2) Liquid Crystal Institute, Kent State University, Kent, Ohio 44242, United States (3) Chemical Engineering, Case Western Reserve University, Cleveland, Ohio 44106, United States

Experimentally, Langmuir films of amphiphilic bent core molecules (Z4), transferred at high pressures to a glass substrate by the inverse Langmuir/Schaefer method, are good perpendicular alignment layers for both rod-like 5CB (4-Cyano-4'-pentylbiphenyl) and a bent-core nematic liquid crystal; this was the first successful technique of inducing that alignment for the bent-core nematic. Here we use all-atom molecular dynamics simulations to investigate the molecular mechanisms of this surface alignment. At high pressures, the Z4 monolayers are tethered by the hydrophilic end to the water or glass surface, with their hydrophobic ends at an angle of ~30º with respect to the normal. We find that the first nCB layer inserts into the bent-core layer, straightening it and inducing perpendicular alignment in the bulk liquid crystal. We study the insertion as a function of the length n of the nCB hydrocarbon chain to explore insertion mechanisms.

98. Thermodynamics and kinetics of tunable colloidal self-assembly from measured energy and diffusivity landscapes

Tara D Edwards tiracki1@jhu.edu

Michael A Beavn. Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland 21218-2608, United States

The ordering of colloidal components could serve as the basis for synthesizing meta-materials. However, an approach does not exist to obtain defect-free structures due to the lack of models that accurately describe the assembly dynamics. We report on the dynamics of tunable depletion-mediated colloidal self-assembly using local and global order parameters. Specifically, temperature-dependent hydrogel nanoparticles are used to thermoreversibly tune attraction between colloids confined within topographically patterned periodic square-wells. In doing so, we can manipulate colloidal microstructures from crystalline to fluid configurations and capture dynamics from assembly/dis-assembly trajectories. The trajectories are fit to the Langevin equation to construct free energy (FEL) and diffusivity (DL) landscapes that describe the microstructures' thermodynamics and kinetics. Our ability to model the evolution of colloidal microstructures provides a basis for feedback-controlled colloidal self-assembly processes that could enable the formation of defect-free meta-materials.

99. Surface diffusion enhancement of the kinetics of lock and key binding

Laura Colón-Meléndez1 lmcm@umich.edu

Jun Liu1, Daniel Beltran-Villegas1, Matthew Spellings1, Greg van Anders1, Stefano Sacanna1, David J Pine1, Sharon C Glotzer2,3, Ronald G Larson1, Michael J Solomon1. (1) Department of Physics, University of Michigan, Ann Arbor, MI 48109, United States (2) Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States (3) Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109, United States (4) Department of Physics, New York University, New York, NY 10003, United States

The kinetics of anisotropic particle assembly is expected to be slow due to selective and directional interactions between the particles. We investigate the lock-and-key colloidal system [Sacanna et al, Nature (2010)], focusing on understanding the mechanisms that lead to specific lock-key binding. We identify the importance of nonspecific binding as a pathway that leads to specifically bound lock-key pairs. This pathway involves surface-mediated diffusion of the key on the lock particle. The prevalence of this mechanism varies as the depletion interaction strength is changed. For some depleting polymer concentrations, this mechanism can be as important to specific lock and key bond formation as the direct binding mechanism. We compare our results with Brownian dynamics simulations and model the surface diffusion mechanism as a mean-first passage time problem. We propose nonspecific interactions can play a general role in accelerating anisotropic particle assembly.

100. Dynamic Assembly of Charged Gold Nanoparticles and Its Applications

Yiding Liu1,2 yliu038@ucr.edu

Xiaogang Han1, Yadong Yin1,2<. (1) Chemistry, University of California, Riverside, Riverside, California 92521, United States (2) Materials Science and Engineering, University of California, Riverside, Riverside, California 92521, United States

Reversible one-dimensional assembly and disassembly of charged gold nanoparticles was achieved by manipulation of colloidal interactions. The reversibility was ensured by strong short-range repulsion between particles while the driven force for the assembly-disassembly process was provided by external stimuli including salt and heat which could affect the DLVO interactions between particles. Forced disassembly can also happen when external mechanical forces were applied to the assemblies, which is expected to be useful as colorimetric indicators for pressure.

101. One-pot Fabrication of Hierarchically Structured Nanoparticles by Selfassembly

Chuanfang Yang cfyang@home.ipe.ac.cn

Xiaoyu Li Key Laboratory of Green Process & Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, China

Controlled assembly of nano-scale building units to form a desired structure is of interest to many practical applications, a raspberry or strawberry-like hierarchical structure with multi-level dimension and dual-roughness is one of the examples. In this work, a series of raspberry-like SiO2 nanoparticles were fabricated via one-pot sol-gel method by self-assembly of different size nanoparticles. Small SiO2 nanoparticles were made to deposit individually on large amino-functionalized SiO2 surface by electrostatic interaction. The effect of pH and zeta potential of SiO2 nanoparticle suspension on the assembly was examined. It was found that the size of the small SiO2 nanoparticles on the surface of the large SiO2 core can be deliberately changed by regulating the experimental parameters. The assembling process is relatively easy to scale up, and the assembled materials are to be used as the building-block to construct surfaces with special wetting properties.

102. Modeling of tunable structural re-configuration of Janus colloidal particles

Daniel J Beltran-Villegas daniel.jose.beltran@gmail.com

Ronald G Larson. Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States

Colloidal particles can assemble into a myriad of structures by virtue of the many interaction forces available to them, making them ideal building blocks. A complete understanding of the assembly of Janus colloids, as a function of Janus balance and particle concentration is not yet available. In this work we study the phase behavior of Janus particles and the re-configurability of its structures. Our results show the range of stability of several structures, including a fluid of clusters, bilayers and worm-like aggregates. We find the bilayer structures to be stable over a range of phase space and provide a good pre-cursor to hexagonally close-packed structures. These findings enable the understanding of the assembly of Janus building blocks and provide a framework with which to study the kinetics of structure change.

103. Patterned plasmonic arrays in combination with ATRP amplification for high performance SPRi analysis

Jason Cheng quan.cheng@ucr.edu

Department of Chemistry, UC Riverside, Riverside, CA 92521, United States

This talk presents the new developments in the design of high performance SPR chips using lithographic approaches. The fabrication of patterned plasmonic arrays based on spatial variation to manipulate evanescence field will be covered. This design suppresses the electromagnetic field in the surrounding area, lead to background-free images that offer improved optical readout. The chips have been employed for protein detection with an ATRP-based amplification strategy, yielding superb signals for SPR imaging analysis. Analytical performance of the design will also be presented.

104. Control Over Aptamer-Gold Nanoparticle Interactions to Design Sensing Conjugates for Simultaneous Multi-target On-Chip Detection

Jorge L Chavez jorge.chavezbenavides.ctr.per@wpafb.af.mil

Joshua E Smith, Joshua A Hagen, Nancy Kelley-Loughnane. Human Effectiveness Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433, United States

Our group has designed colorimetric sensors for targets ranging from small molecules to proteins, based on the combination of gold nanoparticles and DNA aptamers (Apt-AuNPs). In our design, the Apt-AuNPs aggregation degree, and consequently, the color of the suspensions, is affected by target binding by the aptamer. We have observed that different aptamer clones that bind the same target could be used to optimize the limit of detection and dynamic range of these sensors. The aptamer specific conformation and the degree of structural change upon target binding were determined to be critical for proper assay function and characterized by NMR. The colorimetric data analysis was performed through a portable android-based system using a color conversion algorithm that removed ambiguities in the determination of the output color. This work shows that understanding of the interactions between nanomaterials and biorecognition elements is critical to design robust biosensors.

105. Microbead Patterning with Photolabile Hydrogels for Cell Capture and Release

Dong-Sik Shin csiltanen@ucdavis.edu

S. Christian, Julie Sutcliffe, Alexander Revzin. University of California, Davis, CA, United States

Micropatterned surfaces for assembly of organized cell arrays have played an important role in numerous biomedical assays. Although thorough downstream analysis of specific cells is highly desirable, methods for practical retrieval of such cells are limited. We report a soft-lithographic technique for patterning releasable, bio-functionalized polystyrene microbeads onto a photodegradable poly-ethylene glycol-diacrylate hydrogel for rapid collection of bead-captured cells. Our technique utilizes micro-transfer molding and controlled, oxygen-inhibited radical chain polymerization to anchor beads in ordered arrays without sacrificing the bioactivity of the bead surface. This process yielded 68% bead transfer efficiency with >90% bead surface exposure. RGD peptide decorated beads were patterned and screened with 3T3 fibroblasts to demonstrate whole cell capture on bead surfaces. Individual cell-bound beads were simultaneously identified and separated from arrays by degrading photolabile hydrogel anchors under a fluorescence microscope. We anticipate microbead patterning in photolabile hydrogels will offer a flexible platform for numerous biological studies.

106. Colloidal artificial virus nanoparticle model system for characterizing GM3 mediated virus infection

Xinwei Yu1 yuxinwei611@gmail.com

Amin Feizpour1, Hisashi Akiyama2, Suryaram Gummuluru2, Bjoern Reinhard1. (1) Department of Chemistry, Boston University, Boston, MA 02215, United States (2) Department of Microbiology, Boston University School of Medicine, Boston, MA 02118, United States

An artificial virus model system with defined surface properties based on colloidal nanoparticles is introduced. The artificial virus nanoparticles comprise a monosialodihexosylganglioside (GM3) containing liposome shell wrapped around an 80nm Au nanosphere core. Different from liposomes which are endocytosed by Hela-CD169 cells, the artificial virus nanoparticles trigger a receptor specific particle translocation on cell surfaces upon GM3-CD169 interaction. The specific nature of the artificial virus nanoparticle that comprises a soft shell and a hard core results in virus-like behavior in which the particles are redistributed to confined spots in peripheral cell areas. The plasmonic core facilitates the continuous optical tracking of the artificial virus particle with extraordinary brightness and high temporal and spatial resolution in live cell imaging. The engineerable membrane provides a versatile platform to control the surface charge, lipid composition, and ligand density. Optimized artificial virus nanoparticles enable systematic investigations of virus infection pathways under defined conditions.

107. Graphene-carbon nanotubes-glucose oxidase based third generation amperometric glucose biosensor

Trupti Terse1 tters001@ucr.edu

Kikuo Komori2,3, Ashok Mulchandani2. (1) Department of Bioengineering, University of California Riverside, Riverside, CA 92521, United States (2) Department of Chemical and Environmental Engineering, University of California Riverside, Riverside, CA 92521, United States (3) Institute of Industrial Science, University of Tokyo, Tokyo 153-8505, Japan

We report a novel third generation glucose biosensor prepared by immobilizing glucose oxidase (GOD) on a three-dimensional graphene-carbon nanotubes (G-CNT) hybrid electrode. G-CNT hybrid film was synthesized by chemical vapor deposition (CVD) using a two-step method. First, a graphene film was grown on copper foil followed by CNT on the surface of graphene using iron as catalyst. The hybrid film was electrochemically modified to introduce oxygenated functional groups and then functionalized with GOD through bifunctional linker, 1-pyrenebutanoic acid succinimidyl ester. The direct electron transfer (DET) of GOD was studied using cyclic voltammetry which showed a pair of well-defined and quasi-reversible redox peaks with a formal potential of –490mV corresponding to redox site of GOD. DET was further confirmed by studying the behavior of redox peaks at varying scan rates and pH. The constructed electrode detected glucose selectively even in the presence of interfering electroactive compounds normally present in blood.

108. An electrical impedance spectroscopy based technique for sensing stability of oil-water emulsions

Seyedehsan (Sean) Shahidi shahidi@ualberta.ca

Subir Bhattacharjee subir.b@ualberta.ca

Mechanical Engineering, University of Alberta, Edmonton, Alberta T6G2G8, Canada

Emulsion stability measurement is crucial for a variety of industrial processes. In this study, we present an electrical impedance spectroscopy (EIS) based technique for estimating the phase behaviour of oil-in-water emulsions. The impedance measurement cell contains a 500 micron thick film of the emulsion. Frequency response analysis in conjunction with equivalent circuit modeling is then performed to estimate the capacitance and resistance of the films. The technique is demonstrated for glycerol-water mixtures, as well as emulsions containing castor oil in water. For the emulsions, a simple model relating the capacitance and resistance to the droplet size distribution is developed. The technique is able to capture the phase separation dynamics of the emulsion, enabling an estimation of the ripening behavior from the variation of capacitance and resistance with time. The developed technique provides a simple yet robust experimental platform for applying EIS to study the stability of oil-water emulsions.

109. Controlling Pt atomic layer deposition: From Pt nanoparticles to continuous Pt thin films

Steven M George Steven.George@Colorado.edu

Depts. of Chemistry & Chemical Engineering, University of Colorado, Boulder, Colorado 80309, United States

The high cost of Pt requires the efficient use of this catalytic metal. Pt atomic layer deposition (ALD) can be used to control Pt deposition. Pt film morphology varies depending on the initial substrate. On low surface energy oxide surfaces, Pt ALD forms nanoparticles because Pt has a high surface energy and minimizes its surface area. Nanoparticle size can be controlled by the number of Pt ALD cycles. Nanoparticle coverage can be tuned by preadsorbing hexafluoroacetylacetone that blocks surface sites and decreases the nanoparticle coverage. In contrast, W ALD adhesion layers facilitate the deposition of continuous Pt ALD films. Because W has a higher surface energy than Pt, Pt ALD wets the W layer and grows by a layer-by-layer mechanism. Continuous Pt ALD films can be grown with thicknesses of 1.5-2.0 nm as confirmed by in situ spectroscopic ellipsometry and ex situ x-ray reflectivity and x-ray photoelectron analysis.

110. Surface chemistry of a Cu(I)s-butyl amidinate atomic Layer deposition (ALD) precursor on Ni and NiO surfaces

Yunxi Yao yunxi.yao@ucr.edu

Francisco Zaera. Department of Chemistry, University of California, Riverside, Riverside, California 92521, United States

The surface chemistry of Cu(I)s-butyl amidinate on Ni and NiO surfaces was studied by X-ray photoelectron spectroscopy and temperature programmed desorption. On Ni(110) surface, Cu(I) s-butyl amidinate adsorbs dissociatively, and Cu(I) is reduced to metallic Cu above 300 K. H2, HCN and N2 desorption were detected at about 500 K, 570 K and 830 K, respectively, and some carbon deposits are left on the surface. On NiO, Cu(I) is reduced to metallic Cu above 500 K. At about 650 K, H2O, CO, CO2 and H2 desorption were detected. Between 300 K and 400 K, Cu(I) s-butyl amidinate adsorption on both Ni and NiO surfaces is self-limited, reaching a saturation coverage of 0.15 ML Cu, a potential temperature window for the ALD process. Above 500 K, the Cu uptake shows continuous growth on both surfaces with increasing Cu-precursor exposure, a behavior typical of chemical vapor deposition (CVD) processes.

111. Surface, Adatom and Nanostructure Electronic Properties Measured by Low Energy Ion-Surface Charge Exchange

Jory A Yarmoff yarmoff@ucr.edu

Department of Physics and Astronomy, University of California, Riverside, Riverside, CA 92521, United States

Low energy ion scattering (0.5-5 keV) is a popular surface analysis technique that has traditionally been used to obtain compositional and structural information about the surface of a solid material at the atomic scale. Recent work has shown that charge exchange during the scattering of low energy ions with relatively small ionization potentials also provides a unique probe of surface electronic properties. The sensitivity results from the resonant transfer of elections that tunnel between the projectile's ionization level and states in the material. Numerous examples will illustrate the basic process and demonstrate the variety of problems that can be addressed. These include mapping out inhomogeneous potentials at the surfaces of oxide materials and in the presence of adsorbates, measuring the effects of doping in semiconductor materials, observing correlated electron effects induced by an isolated spin on the projectile, and measuring the quantum states in metal nanoclusters.

112. Temperature dependence of ion neutralization during low enegery ion scattering from nanomaterials

Alex B Arjad alex.arjad@email.ucr.edu

Jory Yarmoff. Department of Physics and Astronomy, University of California, Riverside, Riverside, CA 92521, United States

Neutralization that occurs during alkali low energy ion scattering (LEIS) provides unique insight into the electronic structure of metal nanoclusters, which have applications in catalysis, optoelectronics, and sensors. Despite extensive studies involving a wide range of projectiles, energies and scattering targets, studies of the temperature effects on neutralization are relatively scarce. The resonant charge transfer model, which has been successful in describing neutralization from many materials, predicts that hotter surfaces would neutralize scattered ions more effectively because of thermal excitations in the solid. This has been corroborated for scattering from bulk metals. For 2 keV K+ scattering from Au nanoclusters deposited on SiO2, however, it is found that ions scattered from clusters held at low temperature (115 K) neutralize scattered ions more efficiently than at room temperature. We will present new data for Na+ and Li+ scattering from nanoclusters and provide ideas to explain the anomalous temperature dependence.

113. Adsorption of oxygen-containing molecules on the Ge(100)-2 1 surface

Bonggeun Shong bshong@stanford.edu

Stacey F Bent. Department of Chemical Engineering, Stanford University, Stanford, CA 94305, United States

Germanium has gained much interest due to its favorable electronic properties. However, an unstable native oxide necessitates alternative suface passivation schemes in order to utilize Ge. One possible way to achieve this goal is through chemical functionalization. In this study, we compare the reactions of oxygen-containing molecules on Ge(100)-2 and their possibilities for the passivation of Ge. Phenol is chemisorbed on Ge(100) through O-H dissociative adsorption, and forms stable phenoxy and H moieties. On the other hand, nitrobenzene first reacts with a Ge dimer in the manner of 1,3-dipolar cycloaddition. Subsequently, a considerable fraction of the oxygen atoms of the nitrobenzene adsorbates spontaneously migrate into the surface at room temperature, resulting in a mixture of product. This further reaction of nitrobenzene adsorbates is driven by the exothermicity, while this effect is much smaller for phenol and thus such migration of oxygen is not observed.

114. Multifaceted study on the interaction between DNA and salt- free cat-anionic vesicles

Shuli Dong bshong@stanford.edu

Lu Xu, Lei Feng, Renhao Dong, Jingcheng Hao, Key Laboratory of Colloid and Interface Chemistry (Shandong University), Ministry of Education, Jinan, Shandong 250100, China

A multi-perspective study on DNA with salt-free cat-anionic TTAOH / LA vesicles has been presented using different approaches. A strong phase separation phenomenon occurred as a small amount of DNA was added. The binding saturation point at R=2.3 is determined. Due to steric hindrance effects, both in supernatant and precipitate, DNA molecule retains its elongated configuration. Observed multi-lamellar DNA/vesicle microstructures ascribed a key role to DNA molecules, in which the bound DNA served as a glue to attract more vesicles forming large fused complexes. 1HNMR spectra show that the anionic molecules were expelled from complexes before binding saturation occurs at R = 0.8, quite different from other salt cat-anionic vesicle/DNA systems with anionic component molecules being expelled above binding saturation. The expelled surfactant molecules self-assembled into micelle-like aggregates as R close to 2.0. The efficiency of binding DNA with TTAOH/LA vesicles is much higher than those reported salt cat-anionic vesicles.

115. Determination of the crystallographic stacking at the technologically-important cobalt-copper interface

Emily A Lewis emily.lewis@tufts.edu

Charles Sykes. Department of Chemistry, Tufts University, Medford, MA 02155, United States

The atomic-scale structure of the Co-Cu boundary is of interest due to the use of layered Cu/Co/Cu systems in giantmagnetoresistance devices, as the interface between two metals can significantly affect electron transport. Co deposited on Cu(111) forms bilayer-high triangular islands, which grow in two orientations that are rotated 60° with respect to each other. The formation of triangular islands is dictated by the six-fold symmetry of the underlying Cu lattice and the anisotropic diffusion of Co. The growth of the different orientations indicates that there is a difference in the stacking configuration between the two islands. Using a new approach involving adsorption of hydrogen, we explored the stacking of Co islands with scanning tunneling microscopy. Hydrogen adsorbs dissociatively on Co, binding in both fcc and hcp hollows, and the overlayer structure at the interface between domains of hydrogen at different sites gives new insight into the underlying Co/Cu interface structure.

116. Nanoemulsions: A new media for enhancing solubility and stability of Curcumin

Khushwinder Kaur makkarkhushi@gmail.com

Chemistry, Panjab University, Chandigarh, Panjab 1600014, India

Phospholipid-based nanotherapeutics, such as the encapsulation of bioactive compounds in microemulsions and nanoemulsions, are gaining popularity as nutraceutical delivery systems due to their effectiveness in improving the solubility, stability and bioavailability of the loaded food components. Curcumin, a potential component of Indian diet is not only a potential anticancer but also posses remarkable antioxidant properties. The paper exploits the formulation of curcumin loaded o/w nanoemulsions by sonication method. The particle size and stability of nanoemulsion has been characterized by dynamic light scattering and UV-visible studies. Attempts have also been made to understand the morphology of loaded nanoemulsion. Efforts have also been made to understand invitrodigestive release and loading studies. Also, the radical scavenging activity in this nanoemulsion has been found to be 90%. The protein interaction (protein oxidation) with curcumin loaded nanoemulsion has been characterized by fluorescence and FTIR technique.

117. How superhydrophobicity breaks down

Hans-Juergen Butt butt@mpip-mainz.mpg.de

Periklis Papadopoulos, Lena Mammen, Xu Deng, Doris Vollmer, Max Planck Institute for Polymer Research, Mainz, Germany

A droplet deposited or impacting on a superhydrophobic surface rolls off easily, leaving the surface dry and clean. This remarkable property is due to a surface structure which favors the entrainment of air cushions beneath the drop, leading to the so called Cassie state. To utilize superhydrophobicity the collapse of the Cassie state needs to be prevented. Here, we apply confocal microscopy to image the water surface during the collapse on a super-hydro-pho-bic array of micropillars. While the drop evaporates, its rim recedes via step-wise depinning from the edge of the pillars. Before depinning, finger-like necks form due to adhesion of the drop at the pillar's circumference. Once the capillary pressure is high enough the Cassie state collapses. Depending on the specific geometry the drop slowly sags into the substrate or slides down along the walls of the pillars.

118. Dynamic measurement of the force required for moving a liquid drop on a solid surface

Hans-Juergen Butt butt@mpip-mainz.mpg.de

Dominik W. Pilat, Periklis Papadopoulos, David Schaeffel, Doris Vollmer, Ruediger Berger, Department of Experimental Physics, Max Planck Institute for Polymer Research, Mainz, Germany

We measured forces required to slide sessile drops over surfaces. The forces were measured by means of a vertical deflectable capillary stuck into the drop. The Drop Adhesion Force Instrument (DAFI) allowed the investigation of the dynamic lateral adhesion force of water drops of 0.1 to 2 µl volume at defined velocities. On flat PDMS surfaces the dynamic lateral adhesion force increases linearly with the diameter of the contact area of the solid/liquid interface and, in accordance with molecular kinetic theory, linearly with the sliding velocity. The movement of the drop relative to the surfaces enabled us to resolve pinning of the three phase contact line to individual defects. We further investigated a three-dimensional superhydrophobic pillar array. Depinning of the receding part of the rim of the drop occurred almost simultaneously from 4-5 pillars, giving rise to peaks in the lateral adhesion force.

119. Assembly of Anisotropic Particles under Electric Fields

Fuduo Ma fma@mines.edu

Sijia Wang, David T. Wu, Ning Wu. Department of Chemical and Biological Engineering, Colorado School of Mines, Golden, Colorado 80401, United States

Anisotropic colloids possess anisotropic geometry, chemical compositions or surface functionality. Therefore, they can recognize each other and assemble via directional interactions. By tuning the directional interactions between particles, anisotropic particles can assemble into diversified types of new structures. This poster will focus on the electric field directed assembly of two types of anisotropic particles, rigid dimers and flexible trimmers. For colloidal dimers with rigid bonds, we recently observed rich patterns in both crystalline and non-crystalline forms, which depend on the anisotropies in geometry and surface charges. For colloidal trimmers with flexible bonds, we observed a family of well-defined clusters ranging from 3 to 9 particles, with non-trivial high populations for trimers, tetramers, hexamers, and nonamers. At higher particle and salt concentrations, the colloidal clusters with flexible angles can further assemble and connect themselves into several hierarchical structures, including non-close-packed networks that have not been observed before.

120. Development of calibrated microparticles and application to study surface charge in biological systems

Aliana López de Victoria alope019@ucr.edu

David D Lo. Biomedical Sciences Division, University of California, Riverside, CA 92521, United States

Electrostatic charge interactions can influence particle adhesion to surfaces in aqueous environments; accordingly, discrete patterns of electrostatic charge across a surface may influence local particle accumulation on this surface. Unfortunately, no methods presently exist to reveal such patterns, so we developed poly(lactide-co-glycolide) microparticles with defined ?-potential range, using the water/oil/water solvent evaporation process. Fluorophore addition to formulation, had no effect on ?-potential value, shaped or size of the microparticle. Binding studies with fluorophore loaded microparticles showed specific patterns; for example, anionic microparticles bound preferentially to surfaces coated with Protamine while cationic microparticles bound to ssDNA-coated surfaces. These suggest that, in principle, calibrated microparticles can be used to reveal patterns of electrostatic charge on wetted surfaces. With surfaces coated to mimic the electrostatic charge of biological structures (e.g. mucosal epithelium) and particles calibrated to resemble microbes (e.g bacteria), this approach should be useful in examining electrostatic forces in biological aqueous systems

121. Surfactant as co-dispersant for TiO2 particles

Xiaochun Zhang xiaochun_zhang@ashland.com

Bruce Fillipo, Dick Henderson. Ashland Specialty Ingredients, Ashland Inc, Wilmington, DE 19808, United States

Titanium dioxide (TiO2) particles are widely used as white pigment in architectural coating and personal care applications. The maximized dispersion of TiO2 particles in various formulations is critical to achieve optimal performance. Surfactants not only can improve the interfacial property for better wetting, but also can be used as co-dispersant combined with low molecular weight polymeric dispersant. In this paper, various ethoxylated nonionic or anionic surfactants were evaluated for improving grinding efficiency and properties. Different analytical techniques, including rheology, microscopy, ellipsometry, and surface tension analysis, were utilized to study the mechanism of the interaction between surfactants and TiO2 particles.

122. Preparation and physicochemical properties of lipid nanodiscs

Yohei Tsukui1 j7212660@ed.tus.ac.jp

Kenichi Aburai1, Hideki Sakai1, Masahiko Abe1, Dai Kitamoto2, Tomohiro Imura2. (1) Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan (2) Reseatch Institute for Inovation in Sustainable Chemistry, National Institute of Advanced Science and Technology (AIST), Central 5-2, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan

High density lipoproteins (HDLs) whose size is ranging from 7 to 13 nm are mainly composed of apolipoproteins and lipids, and they are known to play an important role in reverse cholesterol transport in the body. Nanodiscs which are artificially reconstituted HDLs have recently attracted attention as potentially useful assemblies applicable not only to pharmaceutical but also to food and cosmetic industries. In this study, we succeeded in preparing nanodiscs by just mixing DMPC vesicles with chemically synthesized a-helical amphiphilic peptides. The physicochemical properties of obtained nanodiscs were then investigated by size-exclusion chromatography (SEC), dynamic light scattering (DLS) analysis, and negative-stain TEM. We also found that the dispersion stability of the nanodiscs in aqueous solution was controllable and drastically improved by varying pH.

123. Interfacial and emulsifying properties of soybean peptides

Mio Nakayama1 m-nakayama@aist.go.jp

Kenichi Aburai1, Hideki Sakai1, Masahiko Abe1, Dai Kitamoto2, Tomohiro Imura2. (1) Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki Noda, Chiba 278-8510, Japan (2) Research Institute for Innovation in Sustainable Chemistry, National Institute of Advanced Industrial Science and Technology (AIST), Central 5-2, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan

Soybean peptides (SPs) including a good balance of essential amino acids have attracted attention as functional foods which contribute to recover from fatigue. In this study, the interfacial and emulsifying properties of soybean peptides with different degrees of hydrolysis (SP95, SP87, SP75, SP49, and SP23) were investigated by surface tension measurements, dynamic light scattering (DLS) analysis, and freeze-fracture electron microscopy (FF-TEM). SP75, SP49, and SP23 with low degrees of hydrolysis behaved as conventional surfactants and self-assembled into giant micelles having an average diameter of about 70 nm above their critical aggregation concentration (CAC). Moreover, SP23 with the lowest degrees of hydrolysis was found to give the most stable O/W emulsions composed of soybean oil and water. This is probably due to the steric repulsion between adsorbed high molecular weight peptides included in SP23.

124. Costly Myths of Crystal and Colloid Formation

Ingo H Leubner ileubner@crystallizationconsulting.com

Department of Research, Crystallization Consulting, Penfield, NY 14526, United States

Myths abound in crystallization science and technology which are causing severe time and money consuming efforts in crystallization research, product development, and manufacturing. Myths about controlled Batch Precipitations are: • Batch crystallization has low reproducibility • Crystal nucleation is a function of reactor / reaction volume • Crystallization is determined by reactor volume and design • Nucleation mechanisms are independent of crystal growth • Supersaturation must be controlled • Nucleation kinetics information is necessary • Cooling, evaporation, and anti-solvent precipitations are unrelated • There is only one theory for batch crystallization Myths about controlled Continuous Crystallizations are: • Continuous crystallization is always more cost-effective than batch precipitation • Crystal size is a function of reaction concentration • Crystal size approaches zero at zero residence time • All equilibriums in continuous crystallization are reached at four residence times • There is only one theory for continuous precipitations. Experimental Results have debunked these Myths

125. Transparent silica nano- and microchannels with circular cross-section

Periklis Papadopoulos papadopoulos@mpip-mainz.mpg.de

Lena Mammen, Kathrin Friedemann, Stefanie Wanka, Daniel Crespy, Doris Vollmer, Hans-Jürgen Butt. Max Planck Institute for Polymer Research, Mainz, Germany

Nano- and microchannels are widely used for defined and targeted material transport. Applications range from fluidic delivery systems to fluidic cell and particle separation, and drug delivery research. Cylindrical airtight channels are essential for fundamental studies of capillary filling, diffusion, or transport phenomena. Diverse techniques were used to prepare continuous tubular inorganic nano- and microchannels, such as coaxial electrospinning, template-assisted techniques or mechanical pulling. Although these techniques exist, it is still challenging to fabricate nanochannels with a defined, homogeneous diameter in an efficient and scalable process without compromising tightness. In this work a simple template-assisted method to fabricate silica nanochannels is presented. The channels are tight, and possess a tunable, homogeneous diameter. To demonstrate the generic applicability of the method, we used artificial electrospun polymer and natural spider silk fibers as template and monitored the filling kinetics by laser scanning confocal microscopy.

126. Photocatalysis with Au@TiO2 yolk@shell nanostructures

Ji Bong Joo jibongj@ucr.edu

Yadong Yin, Francisco Zaera. UC Riverside, Riverside, CA 92507, United States

Because they have unique catalytic behavior and offer potential control over stability and selectivity, nanocatalysts have received much attention. Yolk@shell nanostructures consisting of a movable core inside a shell with an intermediate void are a good example of this type of nanocatalysts. They offer various advantages, including facile diffusion of reactant molecules, high stability toward thermal sintering of the active metal, and a small individual space that can act as a small nanoreactor with a homogeneous reaction environment. In this work, Au@TiO2 yolk-shell nanostructures have been synthesized by using new synthetic strategies. The physical properties of the Au@TiO2 yolk-shell nanostructures, namely, crystallinity, shell thickness, porosity, and Au size, have been controlled, and their effects on photocatalysis have been investigated. We will report our progress on this project in terms of new synthetic strategy for preparing Au@TiO2 yolk-shell nanostructures, tailored control on physical properties and evaluation of their photocatalytic activities.

127. Corona-treated polyethylene: phase separation and dewetting on top surface

Juliana Silva Bernardes1 juliana.bernardes@lnnano.cnpem.br

Leandra Pereira Santos2, Fernando Galembeck1. (1) National Nanotechnology Laboratory, Center for Energy and Materials Research, Campinas, Sao Paulo 13083-970, Brazil (2) Institute of Chemistry, University of Campinas, Campinas, Sao Paulo 13083-970, Brazil

Polyethylene films exposed to corona discharge acquire large and opposite electrostatic potentials on top and on bottom surfaces, forming a macroscopic charge bilayer. In the present work, both PE surfaces were extensively analyzed and the results reveal that water wetting, chemical composition and roughness of the two surfaces are completely different. The bottom surface potential has the same signal as the base electrode but it is not oxidized, neither is it wetted with water, as opposed to the upper surface. Charging does not change bottom morphology while the upper surface roughness increases, due to the formation of protruding islands that are explained as the result of oxidation followed by phase separation and dewetting.

128. Nanoscale detection of acid-base sites on solid surfaces: a Kelvin force microscopy approach

Juliana Silva Bernardes juliana.bernardes@lnnano.cnpem.br

Rubia Figueredo Gouveia, Fernando Galembeck. National Nanotechnology Laboratory at the National, Center for Energy and Materials Research, Campinas, Sao Paulo 13083-970., Brazil

Kelvin force microscopy (KFM) measurements on acidic or basic solid surfaces reveal that electrostatic potential patterns change as the relative humidity (RH) varies even within a shielded environment. The potential on acid surfaces becomes more negative as the water vapor pressure increases, while it becomes more positive on basic solids. These results verify the following hypothesis: water ion clusters are selectively adsorbed on solid surfaces, due to the partition of OH- and H+ ions associated to water adsorption, which depends on the respective Brsted acid or base character of the surfaces. KFM under variable humidity is thus a convenient alternative to determine acid-base surface properties, with a great advantage: it uses only one amphoteric and simple reagent for determining both acid and base sites. To conclude, this technique provides information on the spatial distribution of acid-base sites at nanoscale, which is relevant to catalysis and adsorption.

129. Ultrafast Core-Level Electron Dynamics at Photocatalytic Material Surfaces

Mihai E. Vaida1 mev@berkeley.edu

Stephen R. Leone1,2,3. (1) Department of Chemistry, University of California, Berkeley, California 94720, United States (2) Department of Physics, University of California, Berkeley, California 94720, United States (3) Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States

The surface electronic properties of metal oxides and metal oxides with added photocatalytic centers such as metal particles are important because of their many potential applications in photochemistry and catalysis. Time resolution, surface sensitivity and element specificity are technical ingredients required to investigate ultrafast photoinduced processes and charge localization at the surface of photocatalytic materials. All these requirements are addressed by the design of a new experimental setup that will be presented in this contribution. The experimental setup consists of a tunable femtosecond soft x-ray source, a pump-probe setup, and an ultra-high vacuum surface science chamber for surface preparation and investigation. The ultrafast electron and hole charge state dynamics, charge transfer, separation, and trapping at photocatalytic surfaces will be investigated by time resolved core-level photoemission spectroscopy The first targets for the investigation will be model systems consisting of bare TiO2(100) as well as TiO2(100) supported Fe or Cu particles.

130. Photo-responsive Pickering emulsions based on ion complex formation

Ryosuke Yamazaki1 j7212691@ed.tus.ac.jp

Takeshi Endo1, Kenichi Sakai2, Hideki Sakai 1,2, Masahiko Abe 1,2. (1) Department of Pure and Applied Chemistry, Tokyo University of Science, Noda, Japan (2) Research Institute for Science and Technology, Tokyo University of Science, Noda, Japan

We have prepared spiropyran-modified colloidal silica (SP-Si) particles as photo-responsive Pickering emulsifiers, based on ion complex formation of amine-carboxylic acid. Visible light irradiation to the SP-Si particles dispersed in toluene results in photo-isomerization from a merocyanine (MC) form to a spiro (SP) form, whereas the MC form appears when the isomerized SP form is irradiated by UV light. The SP-Si particles preferentially yield water-in-oil (W/O)-type emulsions with toluene. The dispersion stability of the emulsion is higher for the SP form than for the MC form, resulting from a change in the affinity of the SP-Si particles with toluene and water. We demonstrate effects of grafting density of the SP units on the photo-responsive emulsion stability.

131. Selective Chemistry for the Atomic Layer Deposition(ALD) of Alumina Oxide on Silicon Surfaces

Lei Guo lguo004@ucr.edu

Xiangdong Qin, Francisco Zaera. Department of Chemistry, University of California,Riverside, Riverside, CA 92507, United States

The chemical behavior of silicon surfaces treated with hexamethyldisilazane and octadecyltrichlorosilane, two common silylation agents, was investigated by contact angle measurements and attenuated total reflection infrared absorption spectroscopy (ATR-IR). Addition of the silanes was confirmed by ATR, after which the contact angle of the silicon surfaces became larger. This indicates an increase in hydrophobicity, which means that most if not all of the surface hydroxyl groups become covered and unavailable for atomic layer deposition (ALD) film growth. The surfaces were also treated with a combination of ozone and ultraviolet (UV) light for up to 45 min. These treatments led to a decrease in contact angle with exposure time, which was varied from 5 to 35 min; no further contact angle changes were seen after exposures longer than 35 min. The silane-coated silicon samples exposed to the UV/ozone treatment are now being tested study for selective ALD of metal oxide films.

132. Fate of carbon nanotube polymer composites in the presence of aerobic microorganisms

Kristofer L Marsh1 kmarsh@chem.ucla.edu

David G Goodwin1,2,Iruhany Boyer1,3, Edward J Bouwer2, D Howard Fairbrother1. (1) Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218, United States (2) Department of Geography and Environmental Engineering, Johns Hopkins University, Baltimore, MD 21218, United States (3) Centro de Química, Instituto Venezolano de Investigaciones Científicas (IVIC), Altos de Pipe, Venezuela

Carbon nanotubes (CNTs) are currently being incorporated into polymer products since they can enhance polymer properties, such as tensile strength and electrical conductivity. Because these nanocomposites will enter the environment as postconsumer waste, their fate will be intimately dependent upon their interactions with microorganisms present in environmental systems such as landfills, soils, and surface waters. To better understand how CNT nanocomposites interact with microbial populations, we have conducted experiments to study how CNT loading impacts the initial viability of the model organism Pseudomonas aeruginosa grown on CNT-polyvinyl alcohol composites. Results indicate that an increase in CNT loading causes an increase in cell death. To assess the longer term impact of the CNTs within composites on microbial populations, biodegradable polymers such as poly-?-caprolactone and their respective CNT composites were compared via mass loss studies, scanning electron microscopy and longer-term viability staining.

133. Effect of various amino acids on the interfacial properties of nonionic surfactant

Kaede Yamaguchi1 j7212687@ed.tus.ac.jp

Takeshi Endo1, Kenichi Sakai2, Koichiro Sagawa3, Kazutami Sakamoto4, Masahiko Abe1,2, Sakai Hideki1,2. (1) Dept. of Pure and Applied Chemistry, Tokyo University of Science, Noda, Japan (2) Research Institute of Science and Technology, Tokyo University of Science, Noda, Japan (3) AJINOMOTO U.S.A.,INC, Japan (4) Faculty of Pharmaceutical, Chiba Institute of Science, Japan

Effect of inorganic salts on the solution properties of nonionic surfactant is known to follow the Hofmeister series. Regarding amino acids as the kind of organic salts, their addition to the surfactant solutions is also expected to have significant effect, though the detail report has not been seen. In this work, we studied the effect of amino acids on the solution properties of nonionic surfactant in terms of static surface tension, cloud point, and phase inversion temperature measurements.The amino acid salt addition to the aqueous hexaoxyethlene dodecylether solutions decreased critical micelle concentration. Cloud point and PIT temperatures of C12E6 also decreased with increasing concentration of the amino acids. Mono sodium L-Glutamic acid and mono sodium L-Aspartic acid have more strong effect than L-Arginine hydrochloride, L-Lysine hydrochloride. Compared with inorganic salts, amino acid salts were shown to have more strong salting-out effect on the nonionic surfactant.

134. Numerical analysis of selective ion transport in nano-channels with charged surfaces

Yoona Yang raralkord@gmail.com

Won S Ryoo. Department of Chemical Engineering, Hongik University, Seoul, Republic of Korea

With increasing interests in nano-pore membranes for ion exchange applications, numerous studies have been directed for the analysis of ion transport through charged nano-channels. It is well known that electrolyte concentration as well as surface charge density on channel walls has strong influence on the ion transport characteristics in nano-channels. In a previous study of measuring effective ion diffusivities through ion exchange membranes (IEM), the diffusivity increased with an increase in electrolyte concentration. This anomalous behavior makes it more difficult to construct a proper model that describes selective ion transport through charged nano-channels as IEM. In this study, ion transport properties in cylindrical nano-channels with charged surface were investigated by numerical method for various salt concentrations. Electrical potential and ion distribution were calculated based on Poisson and Nernst-Planck equations, and the resulting fluxes of Na+ and Cl- were evaluated to validate the non-Fickian behavior in the selective ion diffusion process.

135. Emulsification by chitosan-poly(acrylic acid) polyion complex as active interfacial modifier

Kenichi Sakai1 k-sakai@rs.noda.tus.ac.jp

Maya Ueno1, Yuichiro Takamatsu2, Takeshi Endo1, Hideki Sakai1, Kazutami Sakamoto3, Masahiko Abe1. (1) Tokyo University of Science, Noda, Chiba 278-8510, Japan (2) Miyoshi Oil & Fat Co., Ltd., Katsushika, Tokyo 124-8510, Japan (3) Chiba Institute of Science, Choshi, Chiba 288-0025, Japan

Recently, we have developed a new material concept called "active interfacial modifier (AIM)". AIM is molecularly soluble neither in water nor in most of organic solvent, but is attractive with these solvents. This property enables the material to form "an independent third phase" between immiscible two liquid phases and stabilize the emulsion system. In our current study, we focus on the use of a polyion complex (PIC) as an AIM material. The PIC employed in this study consists of an anionic polyelectrolyte, poly(acrylic acid) (PAA) and a cationic polyelectrolyte, chitosan. We expect that these oppositely charged polyelectrolytes form a PIC and stabilize water/oil interfaces as a result of its amphiphilic nature. We demonstrate the dispersion stability of such emulsion systems as functions of composition ratio of PAA/chitosan, oil concentration, and mixing order, etc.

136. Effects of pressure, temperature and surfactant structure on the stability of carbon dioxide foam for Enhanced Oil Recovery

Bokyung Kim kbk0519@gmail.com

Won S Ryoo. Department of Chemical Engineering, Hongik University, Seoul, Republic of Korea

Due to high crude oil prices and global warming caused by increased CO2 in atmosphere, CO2 flooding is considered one of the most promising technologies for both enhanced oil recovery (EOR) and carbon capture sequestration (CCS) purposes. The CO2 EOR performance may be improved by so-called water-alternating-gas (WAG) process, and many researches aim to develop surfactants that yield stable CO2 foams. In this study, CO2-in-water emulsions were formed by using several commercial non-ionic surfactants with branched hydrocarbon or trisiloxane tails. The stability of CO2 foams was evaluated and compared as a function of pressure, temperature, and surfactant tail structure. We also synthesized cationic surfactants with a varying number of trisiloxane groups for CO2-in-water emulsion formation. Surfactants with trisiloxane tails and/or ammonium cationic heads exhibited better stability than their counterparts.

137. Interfacial properties and the phase behavior of oil-saline emulsions formed by single- and double-tail mixed surfactants

Yeonji Kim duswlsmmr@gmail.com

Won S Ryoo. Department of Chemical Engineering, Hongik University, Seoul, Republic of Korea

Enhanced oil recovery (EOR) has been of great interest since 1980's with rising cost of petroleum exploration, and surfactant flooding is considered the most practical technology to increase oil production. The principle of surfactant flooding is to extract the capillary-trapped residual oil by lowering the interfacial tension (IFT). It is well known the surfactant solution should be formulated to form microemulsion middle phase (Windsor III type) with minimum IFT under the reservoir condition. The most common practice is to customize the chemical formulation by targeting the hydrophilic-lipophilic balance (HLB) for a specific oil reservoir. In this study, dihexadecyl sodium sulfosuccinate was synthesized and used as a low-HLB component to be mixed with single-tail sulfate surfactants. The mixture of single- and double-tail surfactants exhibited tunable properties in HLB and suitability for high-temperature reservoirs.

138. Formation of single gold nanorod-encapsulated titania nanoparticles

Hayato Yamaguchi1 j7212689@ed.tus.ac.jp

Kanjiro Torigoe1, Takeshi Endo1, Kenichi Sakai2, Hideki Sakai1,2, Masahiko Abe1,2. (1) Department of Pure and Applied Chemistry, Tokyo University of Science, Noda/Yamazaki, Japan (2) Research Institute for Science and Technology, Tokyo University of Science, Noda/Yamazaki, Japan

Gold nanorods can absorb the light of arbitrary wavelengths ranging from the visible to the near-infrared region depending on the aspect ratio. Meanwhile, titania is a representative photocatalyst, but exhibits photocatalytic activity only under ultraviolet light. If gold nanorods-titania composite particles can be prepared, the light source available for the photocatalyst can be extended from the conventional ultraviolet region to visible and near-infrared regions, leading to an effective use of sunlight energy. In this study, single gold nanorod-encapsulated titania nanoparticles have been synthesized by mixing emulsion droplets of a titania alcoxide with aqueous dispersion of gold nanorods. Encapsulation of gold nanorods in titania was found to be strongly dependent on the composition of ternary solvents. At an optimal composition, single gold nanorod can effectively be encapsulated in a spherical titania particle . After an appropriate crystallization process of titania, these nanocomposites can be applied for visible-light-responsive photocatalysis.

139. Silica particles as platforms for PAMAM Dendrimer immobilized metal affinity reagents

Lawrence Margerum margeruml@usfca.edu

Department of Chemistry, University of San Francisco, San Francisco, CA 94117, United States

PAMAM dendrimer monolayers were tethered to controlled pore glass beads (CPG) or silica nanoparticles and modified with an Ni-NTA derivative (where NTA is an affinity agent used in IMAC-Immobilized Metal Affinity Chromatography). Open sites on the metal ion bind metal indicator dyes to create an indicator displacement assay platform (IDA). The binding of bromopyrogallol red (BPR) to the Ni(II) coordination site was dependent upon the size of the immobilized dendrimer monolayer and the release was specific for free histidine at pH 7. New affinity tags based on terpyridine, Cu(II) and a series of metal indicator dyes on Si-dendrimers were synthesized and compared to the Ni-NTA for subsequent sensing of amino acids and other substrates of biological interest.

140. Characterization of cell viability through on-chip microelectrode arrays

Rachita Sharma1 rsharma3@ncsu.edu

Weiwei Hu2, Orlin D. Velev1. (1) Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695-7905, United States (2) Cell Culture Development Department, Biogen Idec, Research Triangle Park, North Carolina 27709-4627, United States

Characterization of cell viability is a challenging area facing biotechnology, as no clear definition of cell death exists. Cell death is accompanied with a loss in the integrity of the cell membrane, which alters the electrical properties of the membrane as well as the cell interior. Therefore, changes in cell physiology can be characterized by monitoring the cell dielectric properties. Determination of cell viability and dielectric properties using AC electric fields is a rapidly developing research area. We correlated the dielectric properties of the cells, sedimented over the interdigitated electrodes of a microchip, to the voltage across the chip. These voltage waveforms were processed to obtain the circuit impedance, which was used to quantify the changes in cell viability. The results point out that chips with microscopic interdigitated electrodes enable precise characterization of cell life status, and can supplement the existing macroscopic capacitance probes used in bioreactors.

141. Fabrication of Calcinated Gold Nanoparticle Films for Cross-Platform Biosensing

Sam Hinman samuel.hinman@email.ucr.edu

Chih-Yuan Chen, Jicheng Duan, Joseph Kim, Quan Cheng. Department of Chemistry, UC Riverside, Riverside, CA 92521, United States

Gold nanoparticle (AuNP) films possess excellent optical and electronic properties, allowing for versatile, cross-platform measurements utilizing multiple techniques such as surface plasmon resonance (SPR), mass spectrometry, and Raman spectroscopy. We have developed a novel and simple method derived from the concept of layer-by-layer assembly to produce an ultrathin AuNP layer that it is highly stable and reusable. SEM and AFM characterization shows the nanoscale morphology of these films created from 5nm and 13nm AuNPs, which were found consistent in thickness and diameter. SPR was used to monitor the time-dependent AuNP immobilization on the surface, showing the capability of active plasmonic response from various distributions of immobilized gold nanoparticles. In addition, this AuNP film showed excellent and promising results as a surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) substrate, allowing for the detection of the low molecular weight peptides and cytochrome c digest.

142. Calcium phosphate encapsulated soy lecithin emulsion for an oxygen carrier

Kyu-Bum Han1 kyubumhan81@gmail.com

Curtis Takagi3, Hiroshi Mizukami3, Agnes Ostafin2,3. (1) Department of Materials Science and Engineering, University of Utah, Salt Lake City, UT 84112, United States (2) Department of Chemical Engineering, University of Utah, Salt Lake City, UT 84112, United States (3) Nanoshell LLC., Layton, UT 84041, United States

Substituting blood with a fluorinated liquid has been studied for oxygen transport in blood capillaries because of the high volume of oxygen that can be dissolved. Current fluorinated blood substitutes have low stability in vivo due to immune response. To overcome this problem, an oil-in-water emulsion was encapsulated by a thin layer of calcium phosphate (CaP), a biocompatible material, to minimize the immune response and to deliver oxygen to the target area safely and efficiently. A ternary diagram for the perfluorooctyl bromide-based emulsion, including water and soy lecithin, was prepared by mapping the phases present at various compositions. The emulsion was 200nm in diameter, verified with dynamic light scattering to prevent undesired side effects. The CaP coating processing was studied by analyzing the ionic affinity on the emulsion surface. The CaP encapsulated emulsion was observed via transmission electron microscope; it was subjected physical and thermodynamic tests.

143. Size reduction of stimulus-responsive biocompatible polymer microcapsules prepared with electro-capillary emulsification method

Miyuki Watanabe1 7212699@ed.tus.ac.jp

Ayasa Sekita1, Takeshi Endo1, Kenichi Sakai2, Hideki Sakai1,2, Tamotsu Kondo1, Masahiko Abe1,2. (1) Dept. of Pure and Applied Chemistry, Tokyo University of Science, Noda, Japan (2) Research Institute of Science and Technology, Tokyo University of Science, Noda, Japan

The biocompatible polymer capsules have gathered much attention with a view to application as DDS career, stationery, food, and cosmetics. We have so far prepared microcapsules utilizing liquid/liquid interface of the water in oil type (W/O) emulsion droplets prepared by unique emulsification method called electro-capillary emulsification method. The electro-capillary emulsification method enabled us to obtain pH-responsive ethyl-2-cyanoacrylate capsules using the oil solubility surfactant and the size of capsules were about 100nm to 200 nm. On the other hand, we have recently succeeded in size reduction of PLGA and PCL capsules prepared with electro-capillary emulsification method by adding water soluble surfactant Pluronic F88 (F88) to inner aqueous phase. In this study, we studied the effect of the F88 addition in the inner aqueous phase on the size of ethyl-2-cyanoacrylate microcapsules.

144. Phase behaviors of ion complexes forming gemini-like surfactants

Aya Manabe1 j7212679@ed.tus.ac.jp

Yuji Okabe1, Koji Tsuchiya2, Takeshi Endo1, Kenichi Sakai3, Masahiko Abe1,3, Hideki Sakai1,3. (1) Department of Pure and Applied Chemistry, Tokyo University of Science, Noda, Japan (2) Department of Applied Chemistry, Tokyo University of Science, Shinjuku, Japan (3) Research Institute of Science and Technology, Tokyo University of Science, Noda, Japan

Gemini surfactants have attracted much attentions because they have high interfacial properties like low critical micelle concentration (cmc) and low surface tension value at cmc in aqueous solutions. However the synthesis and subsequent purification process of gemini surfactant is more complicated than that of conventional monomeric surfactants. We have recently reported the formation of ion complex having gemini surfactant like structure in mixtures of tertiary amine and a dicarboxylic acid in aqueous solutions. The objective of this work is to investigate phase behavior of N,N–Dimethylhexadecylamine (DMHA) / various dicarboxylic acids /water ternary systems. The gemini like ion complexes showed excellent interfacial activities such as low cmc and low surface tension at cmc than the monomeric type surfactant. In addition, various liquid crystalline phases like hexagonal, cubic, and lamellar ones were observed in concentrated solutions.

145. Optimization of nanoparticle size and count measurements using nanoparticle tracking analysis (NTA)

Duncan A Griffiths1 duncan.griffiths@nanosight.com

Sonja Capracotta1, William Bernt1, Jonathan Smith2, Ian Wilson2, Patrick Hole2. (1) NanoSight Inc., Worthington, OH 43085, United States (2) NanoSight Ltd., Amesbury, Wiltshire SP4 7RT, United Kingdom

Nanoparticle Tracking Analysis (NTA) is the only automated method for counting particles as small as 10 nm and has gained increasing popularity for the study of nanoparticle dispersions, providing high-resolution particle size analysis as well as a direct measure of particle count or concentration. As these measurements have become more important to research in various fields, improvements in reproducibility and accuracy have been achieved through optimization of sampling statistics and analytical protocols. As a particle-by-particle analysis, the statistics required for optimum reproducibility and resolution need to be considered. Analyzing increasing numbers of particles can be achieved by extending analysis times or by multiple sub-samplings. Data shows that a practical limit is reached beyond which increasing analysis time shows a diminished improvement in reproducibility. Multiple samplings show further improvement. Additionally, carrying out analyses under a constant slow flow rather than static provides a further significant improvement.

146. Fabrication of Tyloxapol niosomes for incorporation of anti-TB drugs: Physicochemical and spectroscopic aspects

Neha Jindal nehajindalchem@gmail.com

Surinder K. Mehta. Department of Chemistry and Center of Advanced Studies in Chemistry, Panjab University, Chandigarh, Chandigarh 160014, India

Biocompatible niosomes have been fabricated using Tyloxapol for solubilization enhancement of anti-tuberculer drugs. Drug loaded niosomes have a size of 150 nm with high loading efficiency. FTIR studies infer that the drugs are in harmony with the excipients since no visible interactions between the drugs and excipients have been detected. The prepared formulations are quite stable as assessed by absorption spectroscopy. Micropolarity studies reveal that RIF and INH are located in the film bilayer whereas PZA is adsorbed mainly on the surface head groups. In vitro dissolution studies at physiological conditions have been undertaken to get an idea of in vivo performance. Sustained release has been achieved for hydrophilic drugs and an acceptable release in case of RIF. The formulation is expected to improve the drug bioavailability and may create a sound basis for the better management of the disease, making DOTs more viable and affordable.

147. Effect of Ionic Liquid Electrolytes in DSSCs with Titanium Dioxide (TiO2) inverse opal structures

Naomi Ramesar nehajindalchem@gmail.com

Ilona Kretzschmar. Department of Chemical Engineering, City College of New York - CUNY, New York, New York 10031, United States

Dye-sensitized solar cells (DSSCs) are low-cost innovative solar cells that can work effectively in low-light conditions. The current liquid electrolyte cell has plateaued at an efficiency of 11.1%. A major problem with these cells is the low viscosity and high volatility of the electrolyte, i.e., acetonitrile, which cause leakage and volatilization. Ionic liquids (ILs) are more viscous, less volatile, and conductive and therefore may be more suitable electrolytes. However, the higher viscosity of ionic liquids may cause incomplete infiltration of the DSSC's nanoporous TiO2 electrode. Here, we present a study of DSSCs with TiO2 inverse opal electrodes of controlled pore sizes (0.1-1 µm) and ionic liquid derivatives of 1-alkyl-3-methylimidazolium tetrafluoroborate (alkyl: ethyl, butyl, and decyl) with viscosities ranging from 25.2 to 721 cP. DSSC stability and functionality is tested using current-voltage characteristics.

147. Effect of Ionic Liquid Electrolytes in DSSCs with Titanium Dioxide (TiO2) inverse opal structures

Naomi Ramesar nehajindalchem@gmail.com

Ilona Kretzschmar. Department of Chemical Engineering, City College of New York - CUNY, New York, New York 10031, United States

Dye-sensitized solar cells (DSSCs) are low-cost innovative solar cells that can work effectively in low-light conditions. The current liquid electrolyte cell has plateaued at an efficiency of 11.1%. A major problem with these cells is the low viscosity and high volatility of the electrolyte, i.e., acetonitrile, which cause leakage and volatilization. Ionic liquids (ILs) are more viscous, less volatile, and conductive and therefore may be more suitable electrolytes. However, the higher viscosity of ionic liquids may cause incomplete infiltration of the DSSC's nanoporous TiO2 electrode. Here, we present a study of DSSCs with TiO2 inverse opal electrodes of controlled pore sizes (0.1-1 µm) and ionic liquid derivatives of 1-alkyl-3-methylimidazolium tetrafluoroborate (alkyl: ethyl, butyl, and decyl) with viscosities ranging from 25.2 to 721 cP. DSSC stability and functionality is tested using current-voltage characteristics.

148. Flow synthesis of SiO2@Au core-shell nanoparticles using a microreactor

Yusuke Asahi y.asahi@cheme.kyoto-u.ac.jp

Tatsumasa Hiratsuka, Satoshi Watanabe, Minoru Miyahara. Department of Chemical Engineering, Kyoto University, Kyoto-shi, Kyoto 615-8510, Japan

We developed a continuous process using a microreactor to synthesize SiO2@Au core-shell nanoparticles. First, a microreactor was used to prepare Au nanoparticles decorated on SiO2 core particles. The advantage of our technique is one step process to modify SiO2 surface without Au nanoparticle formation in the bulk phase, thereby eliminating separation procedures. After that, the microreactor was used to successfully grow Au nanoparticles into smooth shell. In addition, connecting these two steps realized a continuous synthesis of SiO2@Au core-shell nanoparticles.

149. Characterizing yielding of nanoemulsion colloidal gels under large amplitude oscillatory shear (LAOS) with combined rheo-SANS/USANS

Juntae Kim juntaekim@umail.ucsb.edu

Yongxiang Gao, Matthew E. Helgeson. Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California 93106-5080, United States

In this study, we use nanoemulsion “organohydrogels” [Helgeson et al., Nature Materials, 2012, 11(4): 344-352] as a model system to explore the nature of so-called “two-step” yielding in colloidal gels and its dependence on gel structure. In particular, the composition and interactions of nanoemulsion droplets can be adjusted to obtain gels with both homogeneous and heterogeneous microstructure. Using large amplitude oscillatory shear (LAOS) measurements, we show that homogeneous gels show an abrupt transition from elastoplastic strain softening to viscoplastic shear thinning at the yield point. Additionally, heterogeneous gels show an additional nonlinear elastic response over a range of strain amplitude at nearly constant values of the fundamental moduli. By performing the first combined studies of rheo-small and ultra-small angle neutron scattering on yielding colloidal gels, we show that these phenomena arise from a “top-down” cascade of microstructural processes, which can be directly reconciled with the nonlinear viscoelastic response during yielding.

150. Superhydrophobic surfaces for protection and friction reduction in marine environment

Michele Ferrari m.ferrari@ge.ieni.cnr.it

Libero Liggieri, Francesca Ravera, Eduardo Guzman. IENI, CNR, Genova, Genova 16149, Italy

The wettability properties of superhydrophobic (SH) surfaces showing contact angle above 150° and a very small hysteresis are exploited in many applications where, due to the small area these surfaces show when in contact with water, interactions with aqueous environment are usually strongly required. The SH surfaces under investigation were prepared by different preparation methods and studied in presence of pure water, marine waters, solutions and dispersions. Depending on the preparation SH surfaces show different aging resistance due to the composition and thickness of the coating. Wetting studies and surface characterization show how the use of patterned and non patterned surfaces can be used to achieve different aims in terms of fouling prevention and protection of metals in underwater conditions.

151. Controlling Gold Nanoparticle Morphology with the use of Nanosized Liposomes

Monica A Marks mmark001@ucr.edu

Ming Lee Tang. Chemistry, University of California, Riverside, Riverside, California 92507, United States

Gold nanoparticles have unique plasmonic properties. In order to fully harness plasmonic gold nanoparticles for use as sensors, surface enhanced imaging, etc., the size and morphology of gold nanoparticles must be precisely controlled. Several colloidal methods have been proposed to regulate the growth process and achieve particles of desired size; however, these approaches produce a variation in particle size. Recently, nanoparticle growth within liposomes has been studied as a way to produce particles of controlled size and morphology. We plan to optimize the gold nanoparticle growth process by utilizing nanosized liposomes to control nanoparticle growth, and limit size dispersion in a reproducible manner. The liposome shell will function as a sealed environment for particle growth. Further optimization of reaction parameters such as temperature, and the concentrations of capping agents, reducing agents and precursors will be explored.

152. Effect of functionalization of the SiO2 nanoparticles on the adsorption of Ru onto them and their activity in degradation of congo red

Sakshi Gupta1,2 chem.sakshi@gmail.com

Surinder K Mehta1, Michael Gradzielski2, Cristina Giordano3. (1) Department of Chemistry and Centre of Advanced Studies, Panjab University, Chandigarh, India (2) Stranski-Laboratorium für Physikalische und Theoretische Chemie, Institut für Chemie, Technische Universität Berlin, Berlin, Germany (3) Department of Colloid Chemistry, Research Campus Potsdam-Golm, Max-Planck Institut (MPI) für Kolloide und Grenzflächen, Potsdam, Germany

The catalytic activity of the Ru nanoparticles supported on SiO2 particles has been investigated as an application in waste water treatment. The microwave synthesized Ru nanoparticles were adsorbed on bare, lysine and arginine functionalized SiO2 nanoparticles. The purpose of functionalization was to increase the interaction of the SiO2 and Ru nanoparticles. Using transmission electron microscopy, energy-dispersive X-ray spectroscopy and dynamic light scattering, it was found that Ru nanoparticles are adsorbed maximum on arginine functionalized SiO2 nanoparticles. The mechanism for this adsorption has been understood by zeta potential on their surface. The catalytic activity of these particles was studied by taking a model degradation reaction, i.e. the reduction reaction of congo red, an azo dye. The kinetics of the reaction was calculated using UV-vis spectroscopy and SiO2-Ru nanoparticles were found to be more active in the degradation of congo red than amine functionalized SiO2 nanoparticles adsorbed by Ru nanoparticles.

153. Langmuir monolayers of mixed systems formed by lung surfactant-like lipid and nanoparticles: A physico-chemical approach to a toxicological problem

Michele Ferrari m.ferrari@ge.ieni.cnr.it

Eduardo Guzman, Libero Liggieri, Francesca Ravera, Eva Santini, IENI, CNR, Genova, Genova 16149, Italy

Langmuir monolayers composed by different mixture of lipids can be used to model the interfacial behaviour of lung surfactant (LS). Taking advantage of this approach, it is possible to evaluate the modifications induced by nanoparticles with different nature in the interfacial properties of such lipid layers. The results points out that the nanoparticles incorporation alters the monolayer phase behavior that is related to changes in the self-organization of the lipid molecules, as confirmed by Brewster Angle Microscopy and AFM. This also modifies the dynamic response that is directly related to the interactions between the nanoparticles and the lipid molecules of the monolayer which provides a more complex surface dynamics as result of the heterogeneous interfacial composition. The effects on the dynamic response of simulated respiratory cycle have also been investigated. This allows for a first definition of potential damages induced by nanoparticles on the LS response under physiology relevant conditions.

154. The role of particles in stabilizing foams and solid foams: A surface tension studies.

Michele Ferrari m.ferrari@ge.ieni.cnr.it

Dominika Zabiegaj, Francesca Ravera, Libero Liggieri, Eduardo Guzman, Eva Santini, IENI, CNR, Genova, Genova 16149, Italy

The effect of particle segregation at the interface which may stabilize the interfacial layers in foams and emulsions , opposing bubble coalescence, is very important in many fields of interest for industrial applications.This work focuses on the interfacial properties of mixed particle- surfactant dispersions used as precursor for the production of particle stabilized foams and porous materials. Foams and green body foams have been produced by combining the particle stabilized foam method with gel casting.The authors investigate the relationship between the interfacial properties of nanoparticles (NP) mixed systems, the stability and 3D structure of liquid and solid (green body) foams obtained by carbonaceous NPs, characterized by different degree of hydrophobicity. The results provide new insight into the role of the composition of the initial dispersion, as precursor for porous material production and of the nature and concentration of the surfactant used with NP to stabilize the foams.

155. Examination of XPS imaging as a tool for the characterization of surfaces lacking lateral features using a model miscible polymer blend

Denise E Brylinski1 dbrylin@hotmail.com

Joseph A Gardella, Jr.2. (1) Department of Math and Natural Sciences, D'Youville College, Buffalo, NY 14201, United States (2) Department of Chemistry, University of Buffalo, SUNY, Buffalo, NY 14260, United States

Instrumental advances have resulted in increased spatial resolution for XPS imaging which, when combined with the quantitative nature and chemical specificity of the technique, makes XPS an attractive tool for the 2-dimensional characterization of surfaces. XPS imaging has been used previously to characterize surfaces with laterally separated features as well as polymer blends with anticipated lateral domain formation. In this work we use XPS imaging in addition to small-spot high resolution XPS to characterize thin solvent-cast films of a 50:50 poly(vinyl chloride)/poly(methyl methacrylate)(PVC/PMMA)blend using methyl ethyl ketone(MEK) as the common casting solvent. In addition to examining the effects of pixel size and principle component(PCA) noise reduction performed on grids with known features, TOF-SIMS C-60 depth profiling with imaging was also performed on the polymer blend to allow us to examine the limitations of XPS imaging for what we conclude to be a rather homogeneous system.

156. Coupling plasmonics with heterogeneous catalysis for versatile solar to chemical energy conversion

Matthew Kale mkale001@ucr.edu

Phillip Christopher. Department of Chemical & Environmental Engineering, University of California, Riverside, Riverside, CA 92521, United States

Catalytic processes are used throughout 80% of the chemical industry and are primarily driven by thermal energy from fossil fuels. Photocatalytic processes that utilize solar energy offer new pathways to energy efficient and environmentally sustainable chemical reactions. Recently, it was shown that coinage metals (Ag) show high photocatalytic activity under low-intensity visible light illumination. In this work we show that the plasmonic properties of Ag can be coupled with more reactive metals (Pt), creating a new class of bimetallic photocatalysts which utilize visible light to drive a wide range of important chemical reactions. The photocatalytic activity and quantum yield of the novel bifunctional nanomaterials have been compared to pure Ag and Pt catalysts for several catalytic reactions in order to determine the mechanism of plasmon energy transfer. These comparative mechanistic studies will be crucial in forming predictive theories for the coupling of solar energy and the transformation into chemical energy.

157. Fluctuation-Induced Forces Between Inclusions Embedded in Membrane

Tyler J Caro tcaro001@ucr.edu

Jeffrey Wagner, Dong Gui, Roya Zandi, Umar Mohideen. Department of Physics and Astronomy, University of California Riverside, Riverside, California 92507, United States

Several experimental evidences suggest that fluctuation-induced interactions exist in a number of soft matter systems including the forces between lipid domains in vesicles. However, no experimental data has yet confirmed the presence of membrane fluctuation-induced forces acting on membrane inclusions. The primary goal of the research performed is to show experimentally the existence of such forces by using silica beads embedded in a lipid bilayer, an analog for a cell membrane and its protein inclusions. We have implemented a Langevin-based algorithm to investigate the interaction between the embedded particles and compared the relevant results with the experimental data. We would gain a better working image into how proteins self-organize by understanding the forces involved in protein aggregation.

158. Tailoring the size and morphology of Copper nanoparticles using surfactant based templates and investigating their catalytic performance

Ravneet Kaur1,2 virgo_ravneet@yahoo.co.in

Surinder K. Mehta1, Michael Gradzielski2, Cristina Giordano3. (1) Department of Chemistry, Panjab University, Chandigarh, Chandigarh 160014, India (2) Institut fur Chemie, Technische Universitat, Berlin, Berlin 10623, Germany (3) Department of Colloid Chemistry, Max-Planck Institut fur Kolloide und Grenzflachen, Potsdam, Brandenburg 14424, Germany

Nanoscience has witnessed tremendous growth in the past few years. Among the various parameters controlling the size and morphology of nanoparticles, surfactants form one of the key features. Therefore, the efficiency of surfactant based templates in controlling the size and shape of nanostructures has been explored. Copper nanoparticles have been fabricated using Copper surfactant/water/n-heptane system giving rise to various colloidal self-assemblies and thereby producing nanostructures with different morphologies such as spherical, rod-like etc. A particular emphasis has been given to producing nanoparticles which possess a long shelf life in aqueous solution and remain stable to oxidation even in unprotected environment. Further, the catalytic performance of as synthesized nanoparticles has been investigated using a model reduction reaction of nitrobenzenes to aminobenzenes, which was found to be remarkably high. An attempt has also been made to understand the role played by the nanoparticle shape and size on the catalytic performance.

159. Mechanistic study of CO2 hydrogenation on Ru catalyst surfaces using density functional theory

Talin Avanesian tavanesian@engr.ucr.edu

Phillip Christopher.Department of Chemical and Environmental Engineering, University of California-Riverside, Riverside, CA 92507, United States

The catalytic hydrogenation of CO2 to higher value hydrocarbon fuels is of great importance as a potential route to achieve environmental and energy sustainability. In order to design optimal catalysts for the reaction, it is essential to have a detailed, atomistic level insight of the reaction mechanism. In present work the mechanism of CO2 methanation on Ru catalyst surface is studied thoroughly to clarify existing debates in literature about the initial hydrogenation step and the following reaction pathways. The complete energetic pathway of the reaction is obtained by calculating energies of the intermediate species and energetic barriers, using DFT computational and theoretical methods. The results of DFT calculations together with microkinetic analysis help us identify active surface sites, stable species, performance limiting and selectivity controlling steps. The knowledge gained can be utilized to develop performance descriptors of materials, which will be useful in search of efficient catalysts for CO2 methanation.

160. Directed Assembly of a Zinc Oxide Nanorod Network for Use as Dye-Sensitized Solar Cell Working Electrode

Roger Chang roger8chang@gmail.com

Ilona Kretzschmar. Department of Chemical Engineering, City College of New York, New York, NY 10031, United States

Zinc oxide is widely used as a semiconductor in dye-sensitized solar cells (DSSCs) because it is easy to fabricate. Specifically, colloidal ZnO is used in DSSC anodes where a vast surface area is required for the adsorption of photoactive dyes. Facile preparation methods have led to ZnO DSSCs that incorporate various 1D- and 2D-nanomorphologies, while demonstrating efficiencies of >7%. However, these structures often require a flat substrate that limits device flexibility. ZnO nanorods assembled into a network by directional magnetic interactions adjust to non-flat substrates while ensuring electronic connectivity. Here, nanorods prepared by hydrolysis in basic conditions, are aligned in an electric field using the field's frequency to control the packing behavior. Next, the nanorods are capped with iron oxide by physical vapor deposition on both ends. Then the caps are magnetized leading to the directed assembly of a flexible 3D network which is characterized by optical and electron microscopy.

161. Contact line dynamics on droplet spreading: Molecular dynamics and experiment

Susumu Kono1 a7506057@rs.noda.tus.ac.jp

Yohei Miyazaki1, Ichiro Ueno1,2. (1) Department of Mechanical Engineering, Tokyo University of Science, Noda, Chiba 278-8510, Japan (2) Research Institute for Science & Technology, Tokyo University of Science, Noda, Chiba 278-8510, Japan

The wetting of a pure water droplet on a glass substrate is observed experimentally with high-speed cameras from the side and below to obtain time series of a contact angle and a radius. We also carry out a series of simulations on droplet wetting similar to experiment system with classical molecular dynamics method. Noted that a Lennard-Jones fluid considering argon is employed as the fluid molecules in the simulations. The droplet spreading behaviors indicated both by the experiments and simulations are quite similar qualitatively. To consider the force acting on the contact line (CL), we focus on the potential distribution near the CL. We propose a model of the droplet wetting dynamics applying the pressure working on the interface near the CL from thermodynamics.

162. Real-time drinking water case studies

Ana Morfesis1 ana.morfesis@malvern.com

Alon Vaisman1, Joseph Krumrine2. (1) 117 Flanders Rd, Malvern Instruments, Inc., Westborough, MA 01581, United States (2) Water Treatment Facility, City of Aurora, Aurora, CO 80015, United States

Drinking water in the US and developed nations of the world is treated to remove contamination. Zeta potential measurements can both evaluate the effectiveness of the chemicals used to clarify the water supply and optimize the amount of coagulant needed in the clarification process. Seasonal changes affect water quality and rapidly require changes in treatment conditions. Zeta potential can be used to monitor the water manufacturing process allowing for the adjustment of coagulant dosage levels periodically in order to minimize cost of chemicals in a water purification facility. Case studies using batch experiments and in-line (real time) measurements will be presented.

163. Synthesis and applications of colloidal dimers

Sijia Wang siwang@mines.edu

Fuduo Ma, Ning Wu. Chemical and Biological Engineering, Colorado School of Mines, Golden, Colorado 80401, United States

Today anisotropic particles have attracted lots of attentions due to their wide applications in optical display, emulsion stabilization, biomedical imaging and drug delivery. We have successfully synthesized colloidal dimers with different properties targeting for three different applications: self-assembly, colloidal surfactants and nanomotors. Dimers with geometric anisotropy showed interesting assembly behaviors, such as chiral structures, under electric fields. While dimers with interfacial anisotropy or even bulk anisotropy, could be treated as colloidal surfactants. Stimuli-responsiveness was also incorporated into colloidal surfactants by adding functional polymers, such as poly(N-isopropylacrylamide) and poly(acrylic acid) Regarding making nanomotors, colloidal dimers with only one lobe coated by platinum were synthesized in large quantities. This type of dimers showed both strong linear and rotational movements in hydrogen peroxide. We also made colloidal dimers (with one lobe encapsulating fatty acid) moving along pH or temperature gradients based on Marangoni effects.

164. Structure sensitivity of carbon dioxide reduction by H2 on supported Rh, Ru, and Ni catalysts

John Matsubu jmatsubu@engr.ucr.edu

Phillip Christopher. Department of Chemical and Environmental Engineering, University of California Riverside, Riverside, California 92521, United States

The environmental impact and unsustainability of the petroleum industry stress the importance of developing new, sustainable and carbon neutral energy sources A potential route to solve both of these issues is to couple CO2 methanation with sustainable hydrogen production technologies, such as photocatalysis. Although CO2 methanation has been studied for decades, atomic scale details of structure-function relationships are poorly understood. The hypothesis explored in this work is that by developing mechanistic structure-function relationships that relate atomic scale catalyst structure to catalytic performance the design of optimized CO2 methanation catalysts will be facilitated. To test our hypothesis we investigated methanation activity with various particle sizes, metals, and reactant conditions. Initial results demonstrated that particle size has a significant effect on methane selectivity and should aid in the rational design of multifunctional artificial photosynthesis catalysts.

165. Surface coordination of naphthalene on Cu(111): Cyano vs isocyano ligand groups

Katie Marie Magnone kmagn001@ucr.edu

Yeming Zhu, Jonathan Wyrick, Chen Wang, MiaoMiao Luo, Sarah Bobek, Arveen Sangkula, Kamelia Cohen, Jorrell Abucejo, Ludwig Bartels. University of California, Riverside, United States

We report scanning tunneling microscopy (STM) measurements performed in ultra-high vacuum that address the adsorption of two molecular species on the (111) surface of a copper single crystal. These molecules, Cyanonaphthalane and Isocyanonaphthalene coordinate with copper adatoms, while at the same time being adsorbed in near-planar geometries on the surface. Though these species differ only in the sequence of N and C in their functional group, theoretical studies predict fundamentally different impacts on the coordination center. In our measurements we observe at low coverages a propensity for the isocyano-species to form three-fold coordinated centers, while the cyano-species forms three, four and five-fold coordinated centers. These measurements are in agreement with theoretical modeling, which predicts that four-fold coordination of isocyanonaphthalene at a single adatom would involve improbable charge redistribution. At sufficient coverage, the cyano-species forms an extended surface network whereas no order of the isocyano-based coverage has been found.

166. Surfactant micelle characterization using Dynamic Light Scattering

Matt McGann2 matt.mcgann@malvern.com

Bryn McDonagh1, Paul Barrett1, Mike Kaszuba2(1) 1 ATA Scientific Pty Ltd., Sutherland, Australia (2) Malvern Instruments Ltd., Malvern, Worcestershire WR14 1XZ, United Kingdom

Non-invasive back scatter optics (NIBS) maximizes the detection of scattered light while maintaining signal quality. This optical configuration provides exceptional sensitivity required for measuring the size of nanoparticles, such as surfactant micelles, at low concentrations and small sample volumes. These results indicate that the NIBS optics provides exceptional sensitivity required for measuring the size of surfactant micelles and along with careful sample preparation the DLS technique is capable of monitoring changes of less than 1 nanometer.

167. Effect of surfactant structure on relative position of surfactant head groups in mixed micelle of cationic-carbohydrate surfactants micelles

Saikat Das1 saikat.das@uky.edu

, E. Davis Oldham2, Hans-Joachim Lehmler2, Barbara L Knutson1, Stephen E Rankin1. (1) Chemical and Materials Engineering Department, University of Kentucky, Lexington, Kentucky 40506-0046, United States (2) Department of Occupational and Environmental Health, University of Iowa, Iowa, Iowa city 52242, United States

We use NMR to study carbohydrate headgroup positioning and interactions in mixed micelles of alkyltrimethylammonium-based cationic and carbohydrate-based non-ionic surfactants. Measurements are made in D2O by spin-spin relaxation (T2) measurements and 1D / 2D nuclear Overhauser effect spectroscopy. Our main objective is to determine combinations of surfactants that “push” the carbohydrate to the exterior of the micelle so that the carbohydrate is available for interactions during materials synthesis. Chain lengths of both surfactants and the type of linker in the carbohydrate surfactant are varied. Results indicate that the sugar head group is always located inside the corona region of mixed micelle prepared using carbohydrate surfactants with ether linkages even when the tail lengths are tuned to favor carbohydrate exposure. The situation changes when new surfactants are used containing a polar triazole linker, where clear evidence is found that the carbohydrate headgroup is “pushed out” to the exterior of the micelle.

168. Impact of water chemistry on colloidal iron and lead release from drinking water distribution system

Haizhou Liu haizhou@engr.ucr.edu

Department of Chemical and Environmental Engineering, University of California, Riverside, Riverside, CA 92521, United States

Drinking water distribution system is a complex system with surface interactions among metal pipeline materials (e.g., iron and lead), trace organic chemicals and biofilms. These chemical processes can destabilize corrosion products on the pipe surface, trigger toxic metal release and pose public health risks. Traditional control strategies are mainly based on equilibrium theory of soluble species. However, release of metal colloid is largely unknown and its behavior is greatly affected by water chemical parameters, notably dissolved organic matter (DOM). This study examines colloidal mobilization of typical iron(III) and lead(IV) corrosion products in the presence of terrestrial- and microbial-derived DOM, respectively. Results show that DOM adsorbs strongly on the surface of iron and lead oxides, which exhibit susceptibility to colloidal dispersion. Carboxylic and phenolic moieties of DOM are capable of reducing lead(IV) solids and accelerating colloidal release. These findings provide insights into major mechanisms affecting colloidal metal release in drinking water.

169. In-situ transformation of Single-Layer MoS2 films: An XPS and Photoluminescence Study

Quan Ma1 qma004@ucr.edu

Patrick Odenthal2, John Mann1, Edwin Preciado1, Dezheng Sun2,4, Wenhao Lu3, Chen Wang1, Koichi Yamaguchi1, Michelle Wurch3, Tai V Tran3, Tianyang Chen1, Tony F Heinz4, Roland K. Kawakami2, Ludwig Bartels1. (1) Department of Materials Science and Engineering, University of California Riverside, Riverside, CA 92521, United States (2) Department of Physics, University of California Riverside, Riverside, CA 92521, United States (3) Department of Chemistry, University of California Riverside, Riverside, CA 92521, United States (4) Department of Physics, Columbia University, New York, NY 10027, United States

MoS2 has recently gained ample attention by its promising catalytic and electronic properties. In this contribution we show the modification of CVD-grown single-layer MoS2 films by means of sputtering. XPS investigations show that under mild conditions up to ¼ of the MoS2 sulfur can be removed, while leaving the film structurally/spectroscopic unchanged. In-situ photoluminescence measurements reveal the impact of thus created defects on the exciton dynamics in the film, a property important both for electronic and photocatalytic applications.

170. Producing Monolayer Molybdenum Disulfide Films

Chen Wang cwang039@ucr.edu

Wenhao Lu wlu005@ucr.edu

Materials Science and Engineering, UC Riverside, Riverside, CA 92507, United States

Already commonly used industrially in the hydrodesulfurization process, MoS2 is much less costly than the precious metals that currently catalyze the hydrogen evolution reaction. Monolayer films better expose the catalytically active edges of nanoscale MoS2. The Bartels lab has developed a procedure that grows monolayer MoS2 by layering sulfur, molybdenum, and sulfur in a manner similar to preparing a sandwich. To optimize the material for widespread, defect-free growth, this research identifies the effects of growing MoS2 monolayers while varying parameters such as substrate type, temperature, dosing pressures, etc. The atomic resolution of scanning tunneling microscopy gauges the quality of these films by analyzing the type and degree of defects. These findings contribute to an understanding of two-dimensional materials and advances the production, development, and use of MoS2 as a photocatalyst for the production of hydrogen fuel.

171. Using atomic force microscopy to investigate the material properties of HULIS aerosol particles

Lelia N. Hawkins lhawkins@g.hmc.edu

Katherine R. Muller, Amanda Lemire, Stephanie Kong. Department of Chemistry, Harvey Mudd College, Claremont, CA 91711, United States

Secondary organic aerosol particles are traditionally considered liquid droplets with relatively short timescales needed for full equilibration with water vapor, oxidants, and volatile organic compounds. However, recent work has indicated that many SOA particles may in fact be better described as viscous or rubbery solids, with long equilibration times for these interactions. Atomic force microscopy is a powerful tool that can be used to probe individual particles under atmospheric conditions. We present measurements of particle morphology and phase (solid, liquid, or semisolid) determined from height maps and force curves. The analyzed particles include both laboratory simulations of aqueous phase oligomerization and atmospheric samples collected in the Los Angeles basin

172. Different Approaches to CVD growth of single-layer MoS2

John Mann1 jmann003@ucr.edu

Edwin Preciado1, Koichi Yamaguchi1, Tai Tran2, Michelle Wurch3, David Barroso2, Quan Ma1, Velveth Klee1, Ariana Nguyen2, Chen Wang1, Ludwig Bartels2. (1) Department of Materials Science and Engineering, University of California Riverside, Riverside, California 92521, United States (2) Department of Chemistry, University of California Riverside, Riverside, California 92521, United States (3) Department of Bioengineering, University of California Riverside, Riverside, California 92521, United States

The transition metal dichalcogenides have attracted recent attention for their promise in the fields of catalysis, nanoelectronics, optoelectronics, spintronics, valleytronics and hydrogen storage. MoS2 is a prototypical transition metal dichalcogenide. We report on the characterization of mono to few layer MoS2 single crystal islands (micron scale) and polycrystalline continuous films (tens of microns to centimeter scale) grown using various precursors and CVD techniques. We analyze the films and islands using Raman spectroscopy, photoluminescence measurements, atomic force microscopy, low energy electron diffraction, low energy electron microscopy, x-ray photoelectron spectroscopy and electrical transport measurements.

173. Interactions between particles on the substrate and contact line of spreading droplet

Junpei Fukushima1 a7508114@rs.tus.ac.jp

Tetsuya Hibino1, Ichiro Ueno1,2. (1) Department of Mechanical Engineering, Tokyo University of Science, Noda, Chiba 278-8510, Japan (2) Research Institute for Science & Technology, Tokyo University of Science, Noda, Chiba 278-8510, Japan

We need to accumulate knowledge on a phenomenon with interactions between a tiny amount of the liquid and the solid for applications such as µ-TAS. We focus on the interaction between the particles and the contact line of the droplet spreading on the substrate. Pure water and silicone oil are employed as the test fluids. The acrylic particles coated with gold and the glass substrates are used for the test particles and the test substrate, respectively. The particles settled on the substrate dominate the contact line behaviors; we find that the explosive acceleration of the contact line on the substrate after the experiences of the interaction between the contact line and the particles. The deformation of the liquid near the contact line due to the interaction results in the radial expansion in the vicinity of the contact line.

174. Density functional theory study of the cysteines on gold clusters: binding site specific calculation

Chao-Ming Ting elvisjay0610@gmail.com

Department of Chemistry UVic, Canada

Self assembly monolayers (SAM) have a broad range of applications in nanotechnology from sensor development to devices and biomedical fabrication. Cysteine is the only proteinogenic amino acid containing a thiol group, thus its behavior on gold has repercussions on the adsorption properties of proteins and peptides. Experimentally, STM images show that cysteine has a complex phase behavior at adsorption on noble metals. In particular, this behavior depends on a variety of factors such as surface density, temperature, and deposition rate. In this study, we are interested in the binding of the thiol and amino groups on gold and their binding energies. Binding group-specific calculations are performed using density functional theory. We investigate how binding structures and energies depend on coordination at the adsorption sites on the gold surface.

175. Controlled synthesis of gold nanoaggregates

Desiree Van Haute dvanhaute@coh.org

Jacob M Berlin. Department of Molecular Medicine, Irell and Manella Graduate School of Biological Sciences, Beckman Research Institute, City of Hope, Duarte, CA 91010, United States

Controlling nanoparticle aggregation is an area of intense investigation. To date, many strategies make use of sophisticated linkers, such as DNA or long polymers. Here we demonstrate the preparation of gold nanoparticle aggregates using a simple novel cross linker. The aggregates are formed with remarkably low polydispersity and stability. These aggregates may be useful for applications in materials science, analytical spectroscopy and medicine.

176. Single Molecule Studies of the CdS nanorod and ligand interface

Xin Lin xli018@ucr.edu

Ming Lee Tang. Department of Chemistry, UC Riverside, Riverside, CA 92521, United States

The unique optoelectronic properties of nanocrystals makes them useful for lighting, sensing and biomedical applications. However, the photophysics of quantum dots that enables such applications are mainly dominated by their composition and surface, of which the latter is not well-understood and poorly characterized. Single molecule fluorescence microscopy has the advantage of resolving the position of a fluorophore down to 10 nm, below the classical diffraction limit of light. This technique has been widely used in biology. In our research, we use super-resolution to quantify the number and the location of ligands on CdS nanorods, thus providing great insight into the CdS nanorod/ ligand interface. This understanding of the organic-inorganic interface will lead to the rational manipulation and design of new materials.

177. Electrokinetic phenomena in colloidal dispersions near superhydrophobic surfaces

Periklis Papadopoulos papadopoulos@mpip-mainz.mpg.de

Hans-Jürgen Butt, Doris Vollmer. Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz., Germany

The increasing interest in microfluidics requires detailed knowledge of electrophoresis and electro-osmosis in capillaries. Superhydrophobic coatings have been suggested as an effective way to increase slip length and reduce drag. In contrast to the materials used currently in microfluidic devices superhydrophobic surfaces are inhomogeneous not only in morphology, but also in chemical composition. A fluid in contact with such a surface is in the Cassie superhydrophobic state, wetting only the topmost parts of the rough structure, while air is trapped between the fluid and the capillary wall. Recent theoretical studies predicted enhanced electro-osmotic flow on periodic structures in the Cassie. Here we discuss variations in the electroosmotic mobility depending on the charge of the superhydrophobic surface and the surface tension of the liquid [1].

178. Molecular dynamics simulation as a tool to study PEGylation in drug delivery

Alex Bunker alex.bunker@helsinki.fi

Faculty of Pharmacy, University of Helsinki, Helsinki, Uusimaa FI-00014, Finland

We review our recent work using molecular dynamics simulation to study PEGylation in drug delivery. PEGylation, the attachment of poly(ethylene glycol) (PEG) to drugs or the exterior of nanovectors, is well established as a technique to create a “stealth shield” that prologues bloodstream lifetime, hence efficacy. We have studied the surface of a PEGylated liposome, studying the effect of membrane state (gel or liquid crystal), presence of cholesterol in the membrane, density of PEG lipid, and targeting ligands expressed on the PEGylated liposome exterior. We have also studied PEGylated drugs, both how the drug interacts with PEG, and how PEGylation of the drug affects the penetration of drugs into the cell membrane. In all of these studies, we have found that the specific properties of PEG, its solubility in both polar and non-polar solvents, and its acting as a polymer electrolyte, have a significant effect when used in drug delivery.

179. Modeling and Analysis of The Transport Phenomena in The Mammary Glands

Ana Quezada1 aquez005@ucr.edu

Kambiz Vafai2. (1) Department of Bioengineering, University of California Riverside, Riverside, California 92521, United States (2) Department of Mechanical Engineering, University of California Riverside, Riverside, California 92521, United States

The increased number of women diagnosed with breast cancer in industrialized countries is raising the awareness of possible factors influencing this occurrence. It is believed that the different lifestyles and environmental factors are increasing the probabilities of being diagnosed with breast cancer. As a stepping stone of our research work we have developed a multi-layer transport model to analyze the quality of the breast milk. The breast milk in comparison with other sampling strategies allows us to understand the mass transport of toxins once inside the bloodstream of women breastfeeding. The multi-layer model presented describes the transport of caffeine, DDT and Cimetidine. The analysis done takes into account the unique transport mechanism of each of the toxins.

180. Tuneable resistive pulse sensing for high resolution, particle-by-particle, size and ?-potential measurements: Applications to liposome, polymer and viral drug delivery systems

Darby M Kozak1 darby@izon.com

Will Anderson2, Gregory Seth Roberts2, Robert Vogel1,3. (1) Izon Science US, Cambridge, MA 02140, United States (2) Australian Institute for Bioengineering and Nanotechnology, University of Queensland, Brisbane, Queensland 4072, Australia (3) School of Mathematics and Physics, University of Queensland, Brisbane, Queensland 4072, Australia

Accurate characterization of complex and polydisperse particle systems is critical to understanding their function and optimization. Tuneable resistive pulse sensors (TRPS) accurately characterize the size1, charge2 and concentration3 of nano to micro-scale particles.4 Measuring the properties of each particle as is passes through the TRPS provides high resolution analysis often beyond that of other techniques.5 Furthermore, the ability to simultaneously measure size and charge on a particle-by-particle basis is a unique characterization method to better understand the role that these properties play.2 We present the fundamental principles behind TRPS2 and demonstrate how it has been used to improve the analysis of a wide range of synthetic and biological particles.1-6 1. Vogel, AnalChem, 2011, 83, 3499-3506. 2. Kozak, ACSNano, 2012, 6, 6990–6997. 3. Roberts, Biosensors&Bioelectronics, 2012, 31, 17-25. 4. Kozak, NanoToday, 2011, 34, 9687-9689. 5. Anderson, JCollInterSci, 2013, In Press 6. Roberts, Small, 2010, 6, 2653-2658.

181. Electrophoretic Deposition of HA/PLGA Composite Microspheres on Magnesium for Medical Implant/Device Applications

Qiaomu Tian1 timarbory@gmail.com

Huinan Liu1,2. (1) Material Science Engineering Program, University of California Riverside, United States (2) Department of Bioengineering, University of California Riverside, United States

The objective of this study is to produce a uniform and consistent HA/PLGA coating on three-dimensional magnesium (Mg) implants. Mg is biodegradable, mechanically strong, and biocompatible when it slowly degrades, promising for medical implant/device applications. However, current available Mg and its alloys degrade too fast to meet the clinical needs. To control Mg degradation and promote bone ingrowth, hydroxyapatite (HA) and poly (lactic-co-glycolic acid) (PLGA) composite microspheres were synthesized and deposited onto Mg substrates using electrophoretic deposition (EPD) process. The surface morphology, composition, and coating cross-section were examined using a scanning electron microscope with attached energy dispersive X-ray spectrometer. The results showed the presence of calcium, phosphorous , carbon, and oxygen peaks, indicating the successful deposition of HA/PLGA microspheres on Mg. The corrosion resistance of the coated Mg was evaluated using the Tafel test. The results showed that the HA/PLGA composite coating improved the corrosion resistance of Mg.

182. Can we detect albumin mutations from osmotic pressure data?

Noriko U Ozaki nsaus001@ucr.edu

Victor G. J. Rodgers. Department of Bioengineering, University of California, Riverside, Riverside, CA 92521, United States

Previously, our lab has developed the free-solvent model that can capture the non-linear behavior of osmotic pressure. One of the parameters obtained by regression of osmotic pressure to this free-solvent model is ion-binding, which has been shown to contribute to observed osmotic pressure differences. Hypothesizing that the ion-binding is sensitive to a mutation of certain ionizable surface residues, we attempt to evaluate the predictability of an albumin mutation from osmotic pressure data. First, we investigated ion-binding sites in silico based on the electrostatic potential and mobile ion charge density calculations from which we will predict an albumin mutation that is expected to have maximum impact on ion-binding, thus, osmotic pressure. The significant deviation of osmotic pressure of a mutant from native albumin is expected to be observed at high concentrations, validating the possibility of using osmotic pressure data as a tool to detect protein mutations.

183. Synthesis of Single Crystal Sub-centimeter Size Graphene Flakes

Zhengtang Luo keztluo@ust.hk

Department of Chemical and Biomolecular Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong.

Graphene boundaries are the major undesired structures that deteriorate the electronic transport properties of graphene-based electronics devices. We here report a strategy to lessen the graphene boundaries by controlling the nucleation density during the initiation stage of chemical vapor deposition processes, which enable us to obtain graphene flakes with sub-centerimeter in dimension. Electron diffraction pattern of the various part on the graphene flakes overlaps finely, indicating the single crystal nature of those superlarge graphene flakes. These large size single crystal graphene flakes have great potential in liquid crystal application. Key words: graphene, Chemical vapor deposition, growth mechanism, carbon adatom

184. Tunable Self-assembled Nanoparticle Assemblies with Activity in Visible Wavelengths

Zhiyuan Huang1 hzyjlu@gmail.com

Monica Marks2, Ming Lee Tang1. (1) Chemistry, University of California, Riverside, Riverside, CA 92527, United States (2) Materials Science and Engineering, University of California, Riverside, Riverside, CA 92521, United States

The interaction of light with noble metal nanoparticles can be tuned by control of their 3D arrangement. With the use of efficient organic chemical reactions, plasmonic nanoparticles are self-assembled to make metamaterials that are active at visible wavelengths. Plasmon hybridization can be tuned by varying particle size or interparticle distance. Different kinds of organic multidentate ligands are synthesized and attached to the surface of nanoparticles. Then rigid organic scaffolds are designed to secure the nanoparticles in predefined positions by self-assembly in order to manipulate and confine light. For example, chiral metamaterials can be synthesized by using asymmetrical scaffolds or different particles in different sizes. This material can be widely used in enantioselective biosensing, non-linear optics, asymmetric synthesis or surface-enhanced spectroscopies.

185. Templating alignment of sequestered membrane proteins by exploiting diamagnetic anisotropy

Steven S Klara sklara@andrew.cmu.edu

Meagan Mauter. Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States

Our goal is to develop new methods to align and crystallize membrane proteins (MPs) over large areas (mm2) for thin film applications. By exploiting the diamagnetic anisotropy of the native proteins, we can template the alignment of sequestered MPs and impose order on high-density MP arrays by applying an external magnetic field. By slowly increasing MP concentration via dialysis, the magnetic and hydrophobic forces will dominate any thermal fluctuations. Preliminary results show that once the microdomains of the lipid-stabilized MPs are aligned in the magnetic field, thermal annealing of the MP solution will effectively drive the development of self-assembled, densely arrayed MP crystals in sizes on the order of square millimeters

186. Chemical Vapor Deposition of Manganese-Based Films on Silicon Oxide Substrates

Huaxing Sun hsun003@ucr.edu

Xiangdong Qin, Francisco Zaera. Department of Chemistry, University of California, Riverside, Riverside, CA 92507, United States

The growth of manganese-based films on silicon oxide substrates via the chemical vapor decomposition of two Mn metalorganic precursors, methylcyclopentadienylmanganese(I) tricarbonyl, MeCpMn(CO)3, and bis(N,N'-diisopropylpentylamidinato)-Mn(II), was characterized and contrasted by X-ray photoelectron spectroscopy (XPS). MeCpMn(CO)3 proved to be much less reactive than the acetamidinate, even if a gas-phase activation method devised in our group based on the use of a typical nude ion gauge for electron bombardment was employed. On the other hand, although the acetamidinate precursor shows high reactivity and afford higher deposition rates at higher temperatures, it also leads to the incorporation of unwanted nitrogen and carbon in the grown Mn(0) films. A nonstoichiometric mixture of MnOx + SiOx and Mn silicate is formed first upon deposition using either precursor, possibly followed by the formation of a thin subsurface Mn silicide layer. On top of the combined Mn silicate/Mn silicide structure, Mn(0) metallic films can be grown.

187. Unraveling Fischer-Tropsch chemistry on V(100)

Yin Luo yin.luo@email.ucr.edu

Gregory Beran. Department of Chemistry, University of California, Riverside, Riverside, CA 92521, United States

Fischer-Tropsch (FT) synthesis has long been one of most important industrial reactions for synthetic fuel production, but much controversy still surrounds the nature of the hydrocarbon chain-propagation intermediates. A few years ago, temperature programmed desorption and x-ray photoelectron spectroscopy experiments provided surface science evidence for key vinyl intermediates on single-crystal V(100) surfaces. [1] To understand the FT chemistry on V(100) and how it relates to FT chemistry on practical catalysts like cobalt or iron, we use density functional theory and microkinetic modeling to investigate the competition among different possible propene formation routes. In line with the popular alkenyl mechanism, we find that vinyl intermediates are kinetically preferred over ethyl ones. However, we also find that the chain-growth pathway that couples methylidene and methyl has even fast kinetics and may be important in FT chemistry, at least on V(100). [1] M. Shen, F. Zaera, Angrew. Int. Ed. 2008, 47, 6583

188. Low energy ion scattering studies of the surface termination of bismuth selenide

Weimin Zhou wzhou007@ucr.edu

Xiaoxiao He, Zhiyong Wang, Jing Shi, Jory A Yarmoff. Department of Physics & Astronomy, UC Riverside, Riverside, CA 92521, United States

Bi2Se3, the prototypical topological insulator(TI) material, has a layered structure with a basic quintuple layer (QL) unit composed of five atomic layers ordered as Se-Bi-Se-Bi-Se. While the atoms within each QL are covalently bonded, the QLs are attached to each other by relatively weak van der Waals forces. It has therefore been widely assumed that the material cleaves between QLs resulting in a Se-terminated surface. After cleaving at room temperature, however, low energy ion scattering (LEIS) spectra collected in a double-alignment geometry, which is sensitive to only the outermost atomic layer, show only Bi and no detectable Se. It is hypothesized that the material initially cleaves between QLs, but a thermally activated process induces a termination change. Additional LEIS measurements made at low temperature (80K) are able to monitor this change. The stability of the Bi-terminated structure and mechanisms that can lead to this termination change will be discussed.

189. Growth and structural and chemical characterization of single layer MoS2 and Mo2S3 on Cu(111)

Wenhao Lu1 wlu005@ucr.edu

Dezheng Sun3, Quan Ma4, Deaho Kim2, Ludwig Bartels1, Jon Wyrick3, John Mann4, Yeming Zhu3. (1) Department of Chemistry, University of California, Riverside, Riverside, California 92521, United States (2) Pacific Northwest National Laboratory, Richland, WA 99352, United States (3) Department of Physics, University of California, Riverside, Riverside, CA 92521, United States (4) Materials Science and Engeering, University of California, Riverside, Riverside, CA 92521, United States

Single layer MoS2 can be exfoliated mechanically similar to graphene. This presentation shows an alternative avenue for the fabrication of MoS2 monolayers at comparatively low temperature and mild conditions through sulfur loading of a copper substrate using thiophenol followed by the evaporation of Mo atoms and annealing. In addition, this method allows the growth of ordered Mo2S3 films and Mo6S6 nanowries. Using anthraquinone and formic acid as test molecules, we titrate the various MoSx and copper-based structures presented on our substrate in order to determine their affinity for adsorbate interactions. We will also report on ongoing catalytic/TPD investigations of these films.

190. Investigating growth of the metal organic framework HKUST-1 in real-time using a Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D)

Elizabeth Schneider1 elizabeth.schneider@biolinscientific.com

Vitalie Stavila2, Joanne Volponi2, Aaron M Katzenmeyer2, Matthew C Dixon1, Mark D Allendorf2. (1) Biolin Scientific Inc., Linthicum Heights, Maryland 21090, United States (2) Sandia National Laboratories, Livermore, CA 94551, United States

The step-by-step growth of the metal organic framework (MOF) [Cu3(btc)2(H2O)3] xH2O (HKUST-1) on surfaces was observed in real-time using a Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D). MOFs were grown on silica, alumina, and gold surfaces functionalized with –OH and –COOH terminated self-assembled monolayers (SAMs) to determine the effects of surface properties on the nucleation and growth of HKUST-1. Adsorption of copper ions and H3btc (1,3,5-benzenetricarboxylic acid) from solution at 15C onto SiO2 QCM-D sensors resulted in a rigid, thin film of HKUST-1, and the experiment was repeated at 30 and 45C to determine the temperature dependency of adsorption kinetics. QCM-D data revealed that the growth of HKUST-1 is characterized by a rapid nucleation step independent of temperature followed by a pseudo-first-order thermally activated growth reaction. A kinetic model was proposed for the surface growth of HKUST-1 by taking into account the rate constants of individual steps.

191. Intrusion Pressure to Initiate Flow though Pores between Spheres

C.W. Extrand chuck_extrand@entegris.com

Vitalie Stavila2, Joanne Volponi2, Aaron M Katzenmeyer2, Matthew C Dixon1, Mark D Allendorf2. (1) Biolin Scientific Inc., Linthicum Heights, Maryland 21090, United States (2) Sandia National Laboratories, Livermore, CA 94551, United States

In this work, clusters of three and four spheres were used to examine the intrusion into the pores between spheres. Each cluster creates a single pore. Liquid drops were gently introduced from above. If the spheres were too large, drops flowed through as soon as they were deposited. If the spheres were too small, liquid was suspended in the neck of the pore and could not pass through; drops became unstable and fell to one side. Alternatively, if spheres of a certain size were chosen, then capillary forces initially prevented drops of lesser stature from breaking though. However, as these drops grew taller, they eventually reached a height where the gravitational force exceeded the capillary force and the liquid flowed through the pore. A simple model for intrusion pressure was derived. Estimates from the model agreed well with experimentally measured values.

192. Shape of a liquid drop on a microstructured surface at different length scales

Periklis Papadopoulos papadopoulos@mpip-mainz.mpg.de

Xu Deng, Lena Mammen, Dirk-Michael Drotlef, Glauco Battagliarin, Chen Li, Klaus Müllen, Katharina Landfester, Aránzazu del Campo, Hans-Jürgen Butt, Doris Vollmer. Max Planck Institute for Polymer Research, Mainz, Germany

Describing wetting of a liquid on a rough or structured surface is a challenge, because of the wide range of involved length scales. Here Laser Scanning Confocal Microscopy images drops on arrays of pillars. Deviations of the shape of drops from a sphere decay at two different length scales, because of the interplay of pinning of the contact line and the minimization of the air-water interfaces. (Papadopoulos et al., Langmuir 28 , 8392 (2012)).

193. Oxidized cellulose gelation with alcohols and sodium dodecyl sulfate (SDS)

Duygu Celebi1 d.celebi@bath.ac.uk

Karen J. Edler1, Janet L. Scott1, Gianfranco Unali2. (1) Department of Chemistry, University of Bath, Bath, Somerset BA2 7AY, United Kingdom (2) R&D, Unilever UK & Ireland, Wirral, Merseyside CH62 4ZD, United Kingdom

Oxidized cellulose fibrils (Oxcell) form clear; shear-thinning aqueous gels in the presence of low concentrations of surfactants (e.g. SDS) or salts, reducing the quantity of surfactants and other thickeners required in cosmetic and pharmaceutical formulations. Recent studies suggest that the gelation mechanism of Oxcell in the presence of SDS results from charge shielding effects and a depletion flocculation mechanism.1In contrast to many systems, surfactant-Oxcell gelation is not hindered, but enhanced, by addition of low MW alcohols. The interactions between Oxcell and additives in aqueous and alcoholic media were analysed using small angle x-ray and neutron scattering, revealing a transformation of the structure of aggregated cellulose fibrils from networks to sheet-like structures with increasing alcohol concentration. Long chain alcohols enhance the degree of dehydration in these gels and generate stiffer gels. 1 Crawford, R. J.; Edler, K.; Lindhoud, S.; Scott, J. L.; Unali, G. Green Chem. 2012 , 14 , 300

193. Oxidized cellulose gelation with alcohols and sodium dodecyl sulfate (SDS)

Duygu Celebi1 d.celebi@bath.ac.uk

Karen J. Edler1, Janet L. Scott1, Gianfranco Unali2. (1) Department of Chemistry, University of Bath, Bath, Somerset BA2 7AY, United Kingdom (2) R&D, Unilever UK & Ireland, Wirral, Merseyside CH62 4ZD, United Kingdom

Oxidized cellulose fibrils (Oxcell) form clear; shear-thinning aqueous gels in the presence of low concentrations of surfactants (e.g. SDS) or salts, reducing the quantity of surfactants and other thickeners required in cosmetic and pharmaceutical formulations. Recent studies suggest that the gelation mechanism of Oxcell in the presence of SDS results from charge shielding effects and a depletion flocculation mechanism.1In contrast to many systems, surfactant-Oxcell gelation is not hindered, but enhanced, by addition of low MW alcohols. The interactions between Oxcell and additives in aqueous and alcoholic media were analysed using small angle x-ray and neutron scattering, revealing a transformation of the structure of aggregated cellulose fibrils from networks to sheet-like structures with increasing alcohol concentration. Long chain alcohols enhance the degree of dehydration in these gels and generate stiffer gels. 1 Crawford, R. J.; Edler, K.; Lindhoud, S.; Scott, J. L.; Unali, G. Green Chem. 2012 , 14 , 300

194. Carbon black/water nanofluids: Preparation and characterization

Eveline De Robertis erobertis@yahoo.com.br

Rodrigo S. Neves, Carlos E. C. Galhardo, Carlos A. Achete. Materials Metrology Division, Inmetro - National Institute of Metrology, Quality and Technology, Duque de Caxias, Rio de Janeiro 25250-020, Brazil

This work presents an experimental study on the homogenous dispersion of carbon black nanoparticles (Monarch®570, Cabot Corp.) in water using different additives to improve their stability – sodium sulfate derivatives (SDBS and SDS) and polyvinylpyrrolidones (PVPK40 and PVPK90). The nanofluids were prepared using ultrasonic disruptor. The primary particles have diameters between 20 and 50 nm, the treatment to breakdown the agglomerates resulted in different distributions for each additive. The results of size distribution and zeta potential are summarized in the table. Low particle sedimentation was observed in the first week due to nanofluids instability as observed in zeta potential measurement. The best dispersions were obtained using both PVP.

195. Size and count analysis of fluorescent drug delivery nanoparticles in complex biological media

Duncan A Griffiths1 duncan.griffiths@nanosight.com

Sonja Capracotta1, William Bernt1, Patrick Hole2. (1) NanoSight Inc., Worthington, OH 43085, United States (2) NanoSight Ltd., Amesbury, Wiltshire SP4 7RT, United Kingdom

The ability to count and measure size distributions of nanoparticles in various media is critical in order to obtain accurate performance information. Size analysis of both drug and gene delivery nanoparticles are typically performed using conventional methods, such as DLS and TEM. However, the requirements of high particle concentration or lyophilization of a sample are not compatible with the characterization of in vitro or in vivo dosing environments. Recently, the measurement of nanoparticles in complex media has been demonstrated using the fluorescence capability of nanoparticle tracking analysis (NTA). Using NTA, sizing (10 nm to 1 m) and concentration measurements of particles in various media are obtained. The particle-by-particle measurements lead to accurate size distributions for polydisperse, low concentration nanoparticle samples (108 particles/mL) commonly encountered in therapeutic and diagnostic applications.

196. Antimicrobial Behavior of Novel Surfaces Generated by Electrophoretic Deposition and Breakdown Anodization

Jessamine A. Quijano1 jquij002@ucr.edu

Young Soo Joung², Cullen R. Buie², and Sharon L. Walker¹ (1) Department of Chemical and Environmental Engineering, University of California, Riverside, California 92521 (2) Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139

Managing biofouling is critical for medical devices, modern infrastructures and marine vessels. In this study, the mass transfer of a marine bacterium, Halomonas pacfica g, was examined, depending upon surface wettability ranging from superhydrophobic to superhydrophilic. This was achieved using a specially designed parallel plate flow chamber system, allowing for deposition to be quantified under a range of relevant solution chemistries. Halomonas pacifica g was analyzed to determine its attachment behavior along with complementary characterization via electrophoretic mobility and hydrophobicity. Surfaces with varying wettability were generated via breakdown anodization or electrophoretic deposition. Surface properties including surface roughness, contact angle, and capillary diffusivity were quantified. The greatest deposition was observed on a superhydrophilic surface, which had micro and nano scale hierarchical structures composed of titanium oxide. Conversely, a hydrophobic surface with micro porous films overlaid with polydimethylsiloxane appeared to be the most “antimicrobial”. Deposition was found to be due to a combination of hydrophobicity and surface roughness. Mechanisms of cell attachment will be discussed.

197. Plenary- Mechanisms of formation and growth of airborne particles

Barbara J. Finlayson-Pitts bjfinlay@uci.edu

Department of Chemistry, University of California Irvine, Irvine, CA 92697-2025, United States

Airborne particles play a major role in climate through scattering of solar radiation back to space and through acting as seeds for cloud and ice nucleation. Quantifying the role of particles in climate change requires a detailed understanding of their sources as well as mechanisms of growth into the size range at which they scatter light efficiently and serve as cloud condensation and ice nuclei. This is complicated by the fact that more than half of the particle mass is often not due to direct emissions but rather to formation from low volatility products of the oxidation of gaseous organic precursors. We report studies of the mechanisms of formation and growth of particles from organosulfur compounds and amines, as well as from ozonolysis of terpenes. Challenges in carrying out such studies and extrapolating to ambient air as well as future needs will be highlighted

198. Colloidal Plasmonics

Andrea R. Tao atao@ucsd.edu

Bo Gao, Su-Wen Hsu. Department of NanoEngineering, Univ of California-San Diego, San Diego, California 92093-0448, United States

Self-assembly – where components spontaneously organize themselves – can be carried out on a massively parallel scale to construct large-scale architectures using solid-state nanocrystal building blocks. I will present our recent work on the synthesis and self-assembly of nanocrystals for plasmonics, where light is propagated, manipulated, and confined by solid-state components that are smaller than the wavelength of light itself. We show the organization of polymer-grafted metal nanocrystals into hierarchical nanojunction arrays that possess intense “hot spots” due to electromagnetic field localization. We also show that doped semiconductor nanocrystals can serve as a new class of plasmonic building blocks, where shape and carrier density can be actively tuned to engineer plasmon resonances. These examples demonstrate that nanocrystals possess unique electromagnetic properties that rival top-down structures, and the potential of self-assembly for fabricating designer plasmonic materials.

199. Tailoring Molecular Recognition Toward Inorganic Surfaces: the Case of Pt

Yu Huang yhuang@seas.ucla.edu

Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095-1595, United States

Solution synthesis of inorganic nanomaterials with precise maneuver over morphology has always been a central goal in many fields of chemistry and physics since the physical and chemical properties of nanomaterials heavily lean on their size and shape. Small molecules and polymers have been extensively explored for this purpose although the organic-inorganic interface interaction in the colloidal system is still far from being understood. In this talk I will share our efforts in decoding the origin of selective molecular adsorption to noble metal facets. The selection of facet specific short peptides and their abilities in guiding predictable shape control of Pt nanocrystals will be first demonstrated. Then detailed experimental and theoretical studies on binding mechanism will be discussed. The end of the talk, the discovered molecular signature for facet specific adsorption will be applies to the design of small molecules that deliver the expected colloidal synthesis results.

200. Confined growth of silver nanoplates in hollow nanospheres

James Goebl jgoeb001@ucr.edu

Vershan Hatharasinghe, Yadong Yin. Department of Chemistry, University of California Riverside, Riverside, California 92521-0001, United States

Recently, we have developed a method for the confined synthesis of silver nanoplates within hollow nanostructures. Although previous studies have demonstrated the confined growth of nanomaterials, the nanoparticles are typically isotropic and simply grow to match the shape of their container. In our study, we demonstrate a method to precisely synthesize high aspect ratio silver nanoplates within the confines of hollow titanium dioxide nanospheres, allowing us to control the shape of the nanoplates based on the dimensions of the container. By coating small silver nanoplate seeds with a silica template, followed by a subsequent titania coating and removal of the template, we obtain hollow titania spheres containing nanoplate seeds. Using a controlled seeded growth technique, we can grow the plates laterally until their edges reach the walls of the container, after which growth stops. We expect this demonstration to lead to the development of increasingly sophisticated confined nanoscale heterostructures.

201. Site-specific synthesis of metal nanoparticles entrapped in hollow polymer nanocapsules

Sergey Shmakov sshmakov@slu.edu

Ying Jia, Eugene Pinkhassik. Chemistry Department, Saint Louis University, Saint Louis, MO 63103, United States

We describe the synthesis of metal nanoparticles exclusively inside hollow polymer nanocapsules (NCs). These polymer NCs could be prepared by templated synthesis in bilayer of vesicles formed by lipids or ionic surfactants. NCs have pores in their nanometer-thin shells that allow fast transport of small molecules and ions across the membrane while bigger molecules or particles could not enter or escape NCs. Here, we entrapped large molecules capable of reducing metal ions within polymer NCs. The synthesis of metal nanoparticles occurs only inside NCs and leads to selective formation of “nanorattles” containing either individual nanoparticles or small clusters of nanoparticles entrapped in hollow porous nanocapsules. Nanoparticles grown inside NCs do not need stabilizing agents to prevent the large-scale aggregation. Combination of "naked" surface of nanoparticles and filtering function of nanoporous shell of NCs can lead to functional nanodevices, such as nanoreactors or advanced sensors.

202. Predicting environmental transformations of nanomaterials from their intrinsic properties

Gregory V Lowry glowry@cmu.edu

Civil & Environmental Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, United StatesCenter for the Environmental Implications of Nanotechnology, United States

The intrinsic properties of many engineered nanomaterials (ENMs) afford them extraordinary novel properties and reactivity. Correlating intrinsic properties to their environmental impacts is the goal of nanotechnology environmental health and safety research. However, it is the extrinsic properties of nanomaterials, i.e. those that are determined in part by the environment conditions and solution composition such as solubility or electrophoretic mobility that determine the environmental fate of ENMs and their potential toxicity. The transformations of ENMs are largely extrinsically driven and will depend on the solution conditions. Important transformations of ENMs include adsorption of biomacromolecules, sulfidation, biodegradation, and redox reactions. This talk will present results from laboratory and field scale studies within the Center for Environmental Implications of Nanotechnology (CEINT) describing the nature and rates of these transformations, and how the intrinsic properties of the particles affect the properties and potential bioavailability and effects of the resulting transformed ENMs.

203. Heteroaggregation of engineered nanoparticles and natural colloids: Method development using gold nanoparticles and hematite.

Jeffrey A. Nason jeff.nason@oregonstate.edu

Brian M. Smith. School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR 97331, United States

The rapid development of engineered nanoparticles (ENPs) and nanoparticle enabled products/processes must be paralleled with appropriate evaluation of their environmental implications. One area that has received relatively little attention is the interaction between ENPs and natural colloids in aquatic systems. Because ENP concentrations in natural systems will likely be dwarfed by the concentration of natural colloids, understanding the interactions between these species is important for predicting environmental fate, transport and toxicity. This presentation will detail the use of a suite of complementary experimental methods (time-resolved dynamic light scattering and filtration-based fractionation techniques followed by ICP analysis) for quantifying the heteroaggregation of 10 nm citrate-capped gold nanoparticles with 150 nm hematite colloids. Experiments have evaluated the influence of pH, ionic strength, ENP:colloid ratio, and the role of a dynamic capping agent on heteroaggregation behavior. Continuing work is focused on extending these methods to other classes of ENPs and natural colloids.

204. Environmentally relevant nanoparticle surfaces and their interaction with lipid bilayers studied by vibrational sum frequency generation and second harmonic generation

Franz Geiger geigerf@chem.northwestern.edu

Northwestern University, United States

This work reports on our ongoing studies aimed at understanding the fundamental chemistry of nanoparticles interacting with biological interfaces. Nonlinear optical spectroscopies, including sum frequency (SFG) and second harmonic generation (SHG), are employed to study the interactions of noble metal and semiconductor core shel nanoparticles having cationic, neutral, and anionic ligands with biologically relevant symmetric and mixed supported lipid bilayers in situ. Our fundamental science results are discussed in the context of quartz crystal microbalance studies as well as in vivo studies to assess biological endpoints.

205. Stabilization of carbon nanotubes by oil droplets in water

Chongzheng Na chongzheng.na@gmail.com

Tong Wu. University of Notre Dame, Notre Dame, Indiana 46556, United States

Hydrophobic carbon nanotubes (HCNTs) have minimal amounts of hydrophilic surface functional groups; therefore, they are believed not to disperse well in water. Unless HCNTs are coated by amphiphilic NOM, they should quickly separate from water through aggregation, precipitation, and sorption processes. Here, we show that HCNTs can be stabilized by oil droplets introduced into ground and surface waters by both natural processes and human activities. The resulting Pickering emulsion can provide mobility to HCNTs in aquatic systems.

206. Adhesion of magnetic nano-particles on a membrane surface

Eunhyea Chung1,2 eunhyea.chung@gmail.com

Seockheon Lee2. (1) Department of Energy Resource Engineering, Seoul National University, Seoul, Republic of Korea (2) Center for Water Resource Cycle, Korea Institute of Science and Technology, Seoul, Republic of Korea

Use of hydrophilic magnetic nanoparticles as a draw solute in forward osmosis process is often suggested due to their unique characteristics. Nanoparticles can generate high osmotic pressure and they can be separated easily compared to such draw solutes as ionic salts. However, it was found that the magnetic nanoparticles sometime block the membrane pores and hinder the water transport through the membrane. In this study, the adhesion of a nano-sized magnetic particle on a membrane in various conditions has been quantified. Atomic force microscopy is applied to measure the adhesion forces between two surfaces in an aqueous solution, and obtained data are compared to theoretical calculations and forward osmosis flux test results. The result of this study would imply that the flux decline in forward osmosis process caused by particulate draw solutes can be possibly improved by controlling draw solution chemistry.

207. Controlling the stability of colloidal dispersions using charged nanoparticles

John Y. Walz1 john.walz@uky.edu

Francisco Guzman2. (1) Department of Chemical Engineering, University of Kentucky, Lexington, KY 40506-0503, United States (2) Department of Chemical Engineering, Virginia Tech, Blacksburg, VA 24060, United States

In this talk, I will discuss the effects of highly-charged nanoparticles on the stability of a dispersion of micron-sized colloidal particles ('microparticles') in solution. I will demonstrate that the impact of these nanoparticles on the interaction between two microparticles depends on the nature of the microparticle-nanoparticle interaction. By varying the nature of the microparticle-nanoparticle interaction, the microparticle-microparticle interaction can be made attractive or repulsive, meaning a stable system of microparticles can be flocculated or an unstable system can be stabilized. I will also demonstrate results from recent experiments demonstrating how these nanoparticles can be used as a novel particle separation technique. Specifically, I will show that these nanoparticles can produce size separation of a binary dispersion of microparticles in a flow-through packed column. These experimental results are consistent with predictions of a model describing how these nanoparticles alter the equilibrium interaction potential between a microparticle and a plate.

208. Direct, simultaneous measurements of colloidal energy and diffusivity landscapes in macromolecular solutions

Michael A Bevan mabevan@jhu.edu

Daniel Beltran-Villegas, Tara Edwards. Chemical & Biomolecular Engineering, Johns Hopkins University, Baltimore, MD 21218, United States

We report a non-equilibrium analysis to simultaneously measure colloidal forces and hydrodynamic interactions in the presence of both adsorbed and unadsorbed macromolecules. A novel analytical method is implemented to self-consistently obtain the position dependent potential energy (i.e., energy landscape) and diffusivity (i.e., diffusivity landscape) from measured colloidal trajectories normal to a wall. Measurements are performed for particles and surfaces with adsorbed polyethylene oxide (PEO) copolymer as a function of unadsorbed PEO homopolymer concentration. Energy landscapes are well described by a steric repulsion between adsorbed brushes and depletion attraction due to unadsorbed macromolecules. Diffusivity landscapes show good agreement with predicted short-range permeable brush models and long-range mobilities determined by the bulk solution viscosity. Lower than expected mobilities in the vicinity of overlapping depletion zones are attributed to finite macromolecule concentrations in the depletion zone altering non-conservative lubrication forces.

209. Synergestic effects of polymers and nanoparticles on depletions forces

Shunxi Ji shunxiji@vt.edu

John Y Walz. Department of Chemical Engieering, Virginia Tech, United States

This study focused on understanding synergistic effects of nanoparticles and polyelectrolytes on depletion forces between micron-sized colloidal particles. The experiments consisted of measuring the force-vs.-distance profile between a large silica particle and a silica plate in aqueous solutions using colloidal probe atomic force microscopy (CP-AFM). The depletants used were silica nanoparticles (22 nm in diameter) and sodium polyacrylate (Mw of 100k). With low concentrations of either only nanoparticles or only polymer in solution, little, if any, depletion forces were detected. When both polymer and nanoparticles were mixed, however, significant depletion forces were observed. Calculation of the potential energy profile that would result from these forces indicated that the forces would be more than sufficient to induce flocculation of an otherwise stable dispersion of micron-sized particles. Our hypothesis is that polymer chains adsorb to the surface of the nanoparticles, creating much larger, charged complexes that can increase the depletion force.

210. Stabilization of weakly-charged microparticles using highly-charged nanoparticles

David Herman1 dherman@vt.edu

John Y. Walz2. (1) Department of Chemical Engineering, Virginia Tech, Blacksburg, Virginia 24061, United States (2) Department of Chemical and Materials Engineering, University of Kentucky, Lexington, Kentucky 40506, United States

A study was performed to understand the ability of highly-charged nanoparticles to stabilize weakly-charged microsphere dispersions. The experiments involved adding either anionic (sulfate) or cationic (amidine) latex nanoparticles to dispersions of micron-sized silica spheres near the silica IEP. Although both nanoparticles increased the zeta potential of the microspheres above the value at which the silica-only dispersions were stable, only the amidine/silica dispersions were stable. Adsorption tests on silica slides indicated that amidine nanoparticles deposited more densely than sulfate nanoparticles, producing multi-layer surface coverage. Calculated DLVO energy profiles between nanoparticle-coated microspheres predicted stability for both systems. It is hypothesized that the relatively low coverage of the sulfate nanoparticles (=25%) led to bare silica patches on the microspheres that could align during interaction due to Brownian motion. This indicates highly-charged nanoparticles can be effective stabilizers, provided sufficient levels of adsorption, and that zeta potential alone is insufficient for predicting coated microsphere stability.

211. Direct measurement of the depletion force produced by ionic micellar solutions

Gregory K. James1 gkjames@vt.edu

John Y. Walz2. (1) Department of Chemical Engineering, Virginia Tech, Blacksburg, Virginia 24061, United States (2) Department of Chemical and Materials Engineering, University of Kentucky, Lexington, Kentucky 40506, United States

The technique of atomic force microscopy was used to measure the depletion force between a silica particle and a flat silica plate in solutions of tetradecyltrimethylammonium bromide (C14TAB) and sodium dodecyl sulfate (SDS) at varying concentrations. The measured results were compared to the predicted results of the model of Walz and Sharma (J. Colloid Interface Sci. 1994, 168, 485-496.) for charged, hard sphere depletants. For C14TAB the measured depletion force was smaller in magnitude than that predicted by the model. A correction is proposed to the Walz and Sharma model that accounts for the physical property differences between ionic micelles and charged, hard spheres. In solutions of SDS micelles, a similar overestimation of the depletion force was observed but not to the same degree as for the C14TAB solutions. This suggests that the specific properties of varying types of micelles are fundamental in determining the magnitude of the depletion force.

212. Interfacial water: A key reactant to biomineralization.

Jason R Dorvee jason.dorvee@northwestern.edu

Arthur Veis. Cell and Molecular Biology, Northwestern University, Chicago, IL 60611, United States

Biomineralization like all biological processes occurs in the presence of water. Most of the studies about the mechanism of biomineralization; the detailed pathways by which the mineral ions proceed from solution to crystal state, have been carried out in relatively dilute and “clean” solutions. In many of these studies the role of water has not been considered. In vivo, the environment is neither dilute nor “clean”. The fluids found within both the intracellular or intercellular environment contain water that is crowded by intra and inter-cellular material. These microenvironments are made up of components which modulate the activity of ions associated with the formation the mineral, but also regulate the activity and structure of the surrounding water. Thus in biomineralization, water is indeed a direct reactant and must be considered. The formation and crystallization of biogenic minerals from aqueous environments is dictated by the manipulation of bound water layers at interfaces.

213. Chiral hierarchal self-assembly in Langmuir monolayers of diacetylenic lipids

Elizabeth K. Mann1 emann@kent.edu

Prem B. Basnet1, Pritam Mandal1, Dominic W. Malcolm1, Sahraoui Chaieb2. (1) Physics, Kent State University, Kent, OH 44242-0001, United States (2) Division of Physical Science and Engineering, KAUST, Thuwal, Saudi Arabia

A Langmuir monolayer made of chiral lipid molecules forms a hierarchal structure when compressed in the intermediate temperature range below the chain melting temperature. These structures are captured via Brewster angle microscopy. When the liquid monolayer is compressed, an optically anisotropic condensed phase nucleates in the form of long, thin claws. These claws pack closely to form stripes. This appears to be a new mechanism for forming stripes within Langmuir monolayers. In the lower temperature range these stripes arrange into spirals within overall circular domains, while near the chain melting transition the stripes arrange into target-structure. We attributed this transition to a change in boundary conditions at the core of the largest-scale circular domains.

214. Evaporation-induced shape change and fission of droplet interface bilayers

Charles P Collier colliercp@ornl.gov

Jonathan B Boreyko, Paul Mruetusatorn. Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States

A promising technique for studying the properties of cellular membranes is the use of droplet interface bilayers (DIBs), where two or more aqueous droplets form bilayers in oil containing lipids. We form DIBs using droplets smaller than 10 microns in diameter in a microfluidic channel, two orders of magnitude smaller than previous DIB systems. The uniquely large surface-area-to-volume ratio of our DIBs results in strong evaporation effects, with two distinct regimes as the droplets shrink in volume. In the first regime, two adjacent droplets minimize surface energy by becoming a single spherical droplet, with the lipid bilayer still in the middle. In the second regime, the evaporating droplet forces the bilayer to buckle to conserve its mass, until fission, with the budding of ultrasmall vesicles, occurs within the droplet above a critical surface tension to regulate stress in the bilayer. This behavior is reminiscent of exo- and endocytosis in cells.

215. Toughening mechanisms of biological and biomimetic composites via interfacial engineering

Lessa K Grunenfelder1 grunenfe@gmail.com

Christopher Salinas1, Steven Hererra1, Chien Huang2, David Kisailus1,2. (1) Department of Chemical and Environmental Engineering, University of California, Riverside, Riverside, California 92521, United States (2) Department of Materials Science and Engineering, University of California, Riverside, Riverside, California 92521, United States

The complex hierarchical structures and impressive mechanical properties observed in biological constructs can provide inspiration for the next generation of high performance composites. A common theme amongst impact-resistant and tough composites is the ability to dissipate large quantities of energy at the interfaces between mineral and organic constituents. Two such examples provided by Nature include the nacreous layer of mollusks and the crustacean cuticle. In this work, we present a detailed examination of the toughening mechanisms present in these two systems and extend the underlying toughening principles via construction of biomimetic composites. The use of uniquely fabricated interfaces using a hierarchical construction of engineering materials provides superior performance and the potential for multifunctionality.

216. Anti-predation adaptations in an ultrahard and bioluminescent marine snail

Christopher Salinas1 chris.salinas@gmail.com

David Kisailus1,2, Dimitri Deheyn3, Russell Shimada3. (1) Department of Chemical & Environmental Engineering, University of California, Riverside, Riverside, CA 92521, United States (2) Department of Material Science & Engineering, University of California, Riverside, Riverside, CA 92521, United States (3) Marine Biology Research Division, SCRIPPS Institution of Oceanography, La Jolla, CA 92093, United States

Mollusks have evolved a wide range of calcified shells to survive in a variety of habitats. There are two common types of microstructures found in mollusk shells: the less common but evolutionarily older nacreous structure, or the more common cross-lamellar structure. In gastropods, the cross-lamellar structure can range from relatively thin brittle shells that enable transmittance of bioluminescent light to thicker, heavier defensive shells. Through carful control of the cross-lamellar system, the gastropod Hinea Brasiliana has evolved to develop a shell that is not only hard and tough, but also one that acts as a wavelength specific diffuser tuned for green bio-luminescence produced by the snail. This combination of strength and bioluminescence makes this organism multifunctional against predation. Here, we uncover the microstructural and interfacial features that yield combined hardness and optical diffusion. We look to understand these structure-function relationships to produce multifunctional ceramics that have tuned optical properties.

217. Bioinspired Hybrid Materials by Gluing of Anistropic Nanocrystals

Ulrich Tritschler1 ulrich.tritschler@uni-konstanz.de

Igor Zlotnikov2, Paul Zaslansky3, Peter Fratzl2, Helmut Schlaad4, Helmut Cölfen1. (1) Department of Chemistry/Physical Chemistry, University of Konstanz, Konstanz, Germany (2) Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Potsdam, Germany (3) Julius Wolff Institute and Centre for Musculoskeletal Surgery, Charité - Universitätsmedizin Berlin, Berlin, Germany (4) Department of Colloid Chemistry, Max Planck Institute of Colloids and Interfaces, Potsdam, Germany

In natural organic-inorganic composites stiff but very brittle mineral crystals are joined by soft but ductile organic materials. Due to a sophisticated hierarchical structuring and a well controlled coupling at the interface between the two components, these biominerals combine both stiffness and toughness. In our present work, biomimetic composite structures were transferred to the synthetic realm by gluing together nanoparticles (Laponite and vanadium pentoxide) with polymers and fabricating composite materials structured on two hierarchical levels by means of liquid crystal (LC) formation of polymer and inorganic nanoparticles: Alignment of anisotropic nanoparticles (first level) within a structured organic matrix (second level). The polymers used are charged LC polyoxazolines with pendant cholesteryl units, enabling the polymer to form lyotropic phases, and carboxyl units, binding ('gluing') selectively to nanoparticle faces. Different analytical techniques revealed insights into the shear-induced hierarchical structuring of the composite materials from the millimeter and micrometer to the nanometer lengthscale.

218. Wetting of superamphiphobic surfaces

Hans-Juergen Butt1 butt@mpip-mainz.mpg.de

Periklis Papadopoulos1, Xu Deng1, Frank Schellenberger1, Ciro Semprebon2, Martin Brinkmann2, Matteo Ciccotti3, Longquan Chen4, Doris Vollmer1. (1) Max Planck Institute for Polymer Research, Mainz, Germany (2) Max Planck Institute for Dynamics and Self-Organization, Goettingen, Germany (3) Laboratoire PPMD/SIMM, UMR 7615, ESPCI, Paris, France (4) Center of Smart Interfaces, Technical University Darmstadt, Darmstadt, Germany

Superamphiphobic surfaces show contact angles with water, aqueous solutions and non-polar liquids greater than 150. Tilting a superamphiphobic surface by a few degrees is already sufficient for a drop to overcome adhesion and to roll off. Characteristic and essential for the unique properties are microscopic pockets of air that are trapped beneath the liquid drops (Cassie state). Prospective applications include self-cleaning, anti-fouling, and drag reduction in micro fluidics. For applications superamphiphobic layers need to be made in a simple, self-assembled process. This often leads to the use of aggregates of spheres. The optimal design of superamphiphobic layers fabricated from highly porous aggregates of nanospheres is discussed (Soft Matter 2013 , 9, 418). This leads to criteria of how to optimize such layers for a particular application.

219. Experimental study of the effect of geometry on equilibrium and nonequilibrium contact angles on textured surfaces

Brendan Koch1 bmkoch@ualberta.ca

Janet A. W. Elliott2 janet.elliott@ualberta.ca

Alidad Amirfazli1. (1) Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta T6G 2G8, Canada (2) Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 2V4, Canada

This experimental study examined the effects of asperity size and sparsity (both individually and in combination) on contact angle. Using photolithography, regularly patterned silicon surfaces with finely controlled geometries were produced, that when chemically passivated to be hydrophobic allow for exploration of multiple geometric factors on the behaviour of superhydrophobic surfaces. Furthermore, performing dynamic contact angle experiments with multiple liquids (water, ethylene glycol and hexadecane) with a broad range of surface tensions has allowed for the exploration of the bounds of applicability of both the Cassie and Wenzel equations for the wetting of textured surfaces. The results are interpreted in terms of a non-dimensional pinning force (or equivalently non-dimensional pinning energy) of defects in a sense equivalent to that used by Joanny and de Gennes.

220. Thin films of partially fluorinated bolaamphiphiles at the air-water interface and on solid substrates

Jan Paczesny1 jpaczesny@ichf.edu.pl

Krzysztof Sozanski1, Patrycja Niton1, Andrzej Zywocinski1, Robert Holyst1, Benjamin Glettner2, Robert Kieffer2, Carsten Tschierske2, Damian Pociecha3, Ewa Górecka3. (1) Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland (2) Institute of Chemistry, Martin-Luther-University Halle-Wittenberg, Halle, Germany (3) Faculty of Chemistry, University of Warsaw, Warsaw, Poland

Partially fluorinated bolaamphiphiles of different shapes exhibit a layering transition from monolayer to multilayer films when spread at the air-water interface and compressed using Langmuir technique. The monolayers do not collapse during compression and ordered lamellar structures are formed instead. The balance between rigidity and flexibility of the molecules seems to be the key factor to avoid irreversible aggregation and to create ordered multilayers. Several peaks and plateaus corresponding to layering transitions were observed in the Langmuir isotherms. Perfect fits of the X-ray reflectometry (XRR) data to theoretical equations allowed for conclusion that the multilayers were really well-ordered lamellar structures. These investigations lead to general understanding of multilayer formation and indicate that only in exceptional cases it is due to a roll-over process. Ordered films of partially fluorinated bolaamphiphiles appeared spontaneously in proper conditions. The tendency for self-assembly of the bolaamphiphiles could be transferred to other species i.e. nanoparticles.

221. Water drops dancing on ice: how sublimation leads to drop rebound

Carlo Antonini1,2 carlo.antonini@mavt.ethz.ch

Ilaria Bernagozzi1, Stefan Jung2, Dimos Poulikakos2, Marco Marengo1. (1) Departement of Engineering, University of Bergamo, Dalmine, BG 24044, Italy (2) LTNT Laboratory of Thermodynamics in Emerging Technologies, ETH Zurich, Zurich, Other CH-8092, Switzerland

Drop rebound is a spectacular phenomenon that can appear through the so-called Leidenfrost effect and after impact on hydrophobic and superhydrophobic surfaces. Here we show that drop rebound can also be originated by another physical mechanism, i.e. solid substrate sublimation. To prove this idea, drop impact tests were conducted on solid carbon dioxide (commonly known as dry ice). As such, we show how three different physical mechanisms, which apparently share nothing in common (evaporation, superhydrophobicity and sublimation), lead to the same phenomenon (i.e. drop rebound), in an extremely wide range of temperatures, from 300C down to -79C (and even below). The visualization of an air vortex ring around the drop is also reported.

222. Wettability engendered templated self-assembly (WETS) for the fabrication of multi-phasic particles

Sai Pradeep Reddy Kobaku1 saireddy@umich.edu

Gibum kwon2, Philip Wong2, Anish Tuteja2. (1) Macromolecular Science & Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States (2) Materials Science & Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States

We have developed a novel technique to fabricate multiphasic particles using surfaces with patterned wettability as a template. The developed methodology, termed WETS (Wettability Engendered Templated Self-assembly) provides us with an unprecedented ability to manufacture, on a large-scale, monodisperse, multi-phasic particles (homogeneous particles, Janus particles, tri-phasic particles, and quad-phasic particles) of any size, shape or chemistry. Using the WETS process, we have fabricated multiphasic polymer particles with a variety of different polymers, micro-particles, as well as nanoparticles. The fabricated monodisperse particles have dimensions ranging from 20 nm – 200 µm. We have also fabricated different amphiphilic Janus particles, possessing both a hydrophobic and a hydrophilic phase, in a wide range of shapes and sizes. Using such amphiphilic particles of different sizes and shapes as building blocks, we have also obtained and studied a diverse set of self-assembled structures at an oil-water interface.

223. Incompleteness in immature HIV-Gag particles: kinetic or thermodynamic?

Bogdan Dragnea dragnea@indiana.edu

Department of Chemistry, Indiana University, Bloomington, IN 47405, United States

Human immunodeficiency virus type I buds out from the infected cell in the form of an immature particle formed from a polyprotein shell which has the intriguing feature of being incomplete. We hypothesized that the apparent incompleteness has its origin in a topological constraint rather than being a kinetic effect as previously thought. To test this hypothesis, we have assembled the Gag polyprotein on a mono disperse spherical template formed from a P22 phage procapsid and studied the structure of the ground state by atomic force, cryo-electron microscopy, and SAXS.

224. Optical Characterization of GAG protein Induced Plasma Membrane Budding in In-vitro Systems

Umar Mohideen umar.mohideen@ucr.edu

Sharad Gupta, Dong Gui, Roya Zandi. Department of Physics and Astronomy, University of California, Riverside, Riverside, CA 92521, United States

Retroviruses such as human immunodeficiency virus (HIV) and murine leukemia virus are single stranded RNA viruses whose assembly relies on viral GAG protein and its ability to interact with genomic RNA. The shell of the “immature” HIV particle made up of uncleaved Gag proteins is surrounded by a lipid bilayer which is derived from the plasma membrane of the host cell during budding (or exiting) of the virus from the cell. We will investigate the budding process though the interaction of denatured GAG protein with free standing bi-lipid plasma membranes and giant unilamellar vesicles (GUVs) composed of diphytanoylphosphatidylcholine (DPhPC), phosphocholine (POPC) and Cholesterol.

225. Selfassembly of viral shells under non-equlibrium conditions

Jef Wagner jeffrey.wagner@ucr.edu

Andrew Jarjour, Gonca Erdemci-Tandogan, Roya Zandi. Department of Physics and Astronomy, University of California, Riverside, Riverside, CA 92521, United States

Across the virus world the viral shells take on a great many shapes, including icosahedra, cylinders, cones, and irregular spheroidal particles. We have developed a coarse grained physical model for viral capsid growth, treating each protein as a single triangular unit that binds along the edges. The model has only three parameters: the ratio of the bending to stretching moduli, the preferred curvature, and a parameter related to forming a pentamer. We present a survey of the capsid shapes over the full range of parameter space.

226. In vitro packaging of RNA by CCMV capsid protein

Rees F Garmann rgarmann@chem.ucla.edu

Mauricio Comas-Garcia, Charles M Knobler, William M Gelbart. Department of Chemistry and Biochemistry, UCLA, Los Angeles, CA 90095-1569, United States

Cowpea chlorotic mottle virus (CCMV) was the first spherical virus to be reconstituted in vitro (Bancroft, 1967). CCMV capsid protein (CP) has since been shown to package heterologous RNA, a property we exploit when packaging brome mosaic virus RNA1 into virus-like particles (VLPs) consisting of 180 CP molecules and a single RNA. By cryo-electron microscopy, we find that simply equilibrating CP and RNA in the canonical assembly buffer (neutral pH) is insufficient for generating uniform VLPs with icosahedral capsids, and that an additional acidification step is required. These observations are consistent with an “en-masse” assembly mechanism (McPherson, 2005; Elrad and Hagan, 2010) in which CCMV CP initially binds to RNA forming a disordered complex due to the relatively weak CP-CP interactions at neutral pH. This complex acquires icosahedral symmetry upon acidification, when the strength of the CP-CP interactions is known to increase.

227. Self-assembly of virus particles: The role of genome

Gonca Erdemci-Tandogan1 gonca.erdemcitandogan@email.ucr.edu

Jef Wagner1, Rudolf Podgornik2, Roya Zandi1. (1) Department of Physics and Astronomy, University of California, Riverside, United States (2) Department of Physics, University of Ljubljana, Slovenia

A virus is an infectious agent that inserts its genetic material into the cell and hijacks the cell's machinery to reproduce. The simplest viruses are made of a protein shell (capsid) that protects its genome (DNA or RNA). Many plant and animal viruses can be assembled spontaneously from a solution of proteins and genetic material in different capsid shapes and sizes. This work focuses on the role of genome in the assembly of spherical RNA viruses. The RNA, a highly flexible polymer, is modeled by mean field approximations. Two RNA models are discussed: (i) A linear polymer model including a pairing affinity between RNA base pairs, and (ii) a branched polymer model. Polymer density and electrostatic potential profiles are obtained, and the relevant free energies are calculated from these profiles. The optimal length of the encapsidated chain is examined as a function of the model parameters.

228. Water surfaces and impact on aerosol: nitrates, sulfates, and carbonates with mono and divalent counter cations

Heather C Allen allen.697@osu.edu

Wei Hua, Dominique Verreault, Ellen M Adams, Dana M Telesford. Chemistry and Biochemistry, Ohio State University, Columbus, OH 43210, United States

Atmospheric aerosols and their surfaces play significant roles in the atmospheric chemistry and transformation of airborne pollutants, and in influencing climate change. The surface of an aerosol can be comprised of an aqueous and organic phase, a dust particulate, or a soot particle with an aqueous surface film. Within the surface layers, inorganic and organic ions are also typically present. These surfaces are complex and have an organization unique to their interface. Here we present the vibrational nonlinear spectroscopic and Brewster angle microscopy of aqueous surfaces, ion distributions, the interfacial electric fields, and the organization of lipids and fatty acids that are prevalent in urban and marine regions. Conventional and phase-sensitive vibrational sum frequency generation (VSFG and PS-VSFG) are used to investigate the average direction of the transition dipole moment of interfacial water molecules, adding insight into possible and prevalent reaction pathways for atmospheric aerosols.

229. Organic Aerosol from the Deepwater Horizon Oil Spill: Chemical and Microphysical Properties

Roya Bahreini1,2,3 bahreini@ucr.edu

Ann M. Middlebrook,3 Charles A. Brock,3 Joost A. de Gouw,2,3 Stuart A. McKeen2,3 Leah R. Williams,4 Kelly E. Daumit,5 Andrew T. Lambe,4,6 Paul Massoli,4 Manjula R. Canagaratna,4 Ravan Ahmadov,2,3 Anthony J. Carrasquillo,5 Eben S. Cross,5 Barbara Ervens,2,3 John S. Holloway,2,3 James F. Hunter,5 Timothy B. Onasch,4,6 Ilana B. Pollack,2,3 James M. Roberts,3 Thomas B. Ryerson,3 Carsten Warneke,2,3 Paul Davidovits, x6 Douglas R. Worsnop,4 and Jesse H. Kroll5,7. (1) Department of Environmental Sciences, University of California, Riverside, 92507, United States. (2) Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder, Boulder, Colorado, United States. (3) Chemical Sciences Division, Earth System Research Laboratory, NOAA, Boulder, Colorado, United States (4) Aerodyne Research Inc., Billerica, Massachusetts, United States (5) Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States (6) Chemistry Department, Boston College, Chestnut Hill, Massachusetts, United States (7) Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States

The explosion at the Deepwater Horizon (DWH) oil rig in April 2010 resulted in a massive oil spill in the Gulf of Mexico. Here we present results from airborne gaseous and aerosol measurements from one of the NOAA WP-3D survey flights conducted around and downwind of the oil spill site in June 2010. The analysis indicated that intermediate volatility organic compounds emitted from the aged, surface oil contributed to significant formation of secondary organic aerosol (SOA). Mass spectra of the SOA were similar to that of fresh organic aerosol typically observed in urban areas although contribution of oxygenated fragments with a hydrocarbon backbone was relatively higher. In each transect downwind of the spill site, a gradient in SOA oxygen content was observed: higher degree of oxygenation was observed in the SOA downwind of the fresher surface oil. Furthermore, size-resolved composition measurements indicated that growth of the newly formed particles with downwind distance from the site was not due to condensation of heavily oxidized SOA, but rather by condensation of moderately oxygenated hydrocarbon species. To support observations from the field, laboratory oxidation experiments of evaporated crude oil were conducted. Mass spectral comparisons between ambient SOA and laboratory-generated SOA will be presented.

230. Measuring water diffusion coefficients in mixtures of long-chain alcohols

Annabel M. Edwards edwardsa@denison.edu

Devon Widmer, David Calhoun. Department of Chemistry and Biochemistry, Denison University, Granville, OH 43023, United States

Hydrophobic coatings may limit water uptake and diffusion in aqueous atmospheric aerosols. In addition, the water content of some organic aerosols influences the aerosol's phase state. Few experiments have measured the diffusion constant of water in long-chain molecules that serve as model compounds for the organic fraction of aerosols. This presentation will highlight current experiments that measure the diffusion coefficient of water in binary mixtures of long-chain alcohols. We use Fourier-transform infrared spectroscopy in attenuated reflection mode to study the rate of water uptake into liquid and liquid-solid mixtures. Our earlier measurements of water's diffusion coefficient in n-octanol matched literature values indicating the robustness of our technique to liquid systems. Current work focuses on mixtures of tetradecanol and eicosanol and aims to measure diffusion coefficients across a liquid-solid phase diagram of this binary mixture.

231. Understanding the Hygroscopcity of Multi-component Secondary Aerosol from Precursor Mixtures

Shaokai Gao2 shaokaigao@gmail.com

Akua Asa-Awuku1,2. (1) Chemical and Environmental Engineering, University of California, Riverside, Riverside, CA 92507, United States (2) Center for Environmental Research and Technology, University of California, Riverside, United States

High concentrations of isoprene have been measured with beta-caryophyllene emissions. However few studies have looked at the formation of secondary organic aerosol (SOA) and the SOA cloud condensation nuclei (CCN) activities in the presence of both. In this study, gas-phase, aerosol-phase chemistry and their influences on particle wetting (CCN activities) was explored by selected ion flow tube mass spectrometer (SYFT-MS), high resolution time of flight mass spectrometer (HR-Tof-AMS), and a CCN counter (CCNc) respectively. Gas-phase partitioning behaviors into the aerosol phase were investigated. Experimental results showed that the exponential decay rate of isoprene was much slower in the presence of beta-caryophyllene. SOA formed from the beta-caryophyllene and isoprene mixtures have larger, hygroscopicity, kappa values compared with that formed by beta-caryophyllene only. CCNc results also showed that SOA may have multiple activation peaks, suggesting that particle chemical compositions can be varied with size distributions.

232. Pollen Detachment from Surfaces: Effects of Surface Roughness, Ornamentations and Pollenkitt Coating

Haisheng Lin hlin74@mail.gatech.edu

J Carson Meredith. School of Chemical & Biomolecular Engineering, Gerogia Institution of Technology, Atlanta, GA 30332, United States

Pollen, exhibiting a remarkable breadth of complex surface features, is dispersed as a dusty material and carried by either wind or insects. In addition, many pollen grains are coated with a viscous liquid, 'pollenkitt', thought to play important roles in pollen dispersion and adhesion. We develop a new approach to measure the pollen detachment from various surfaces using centrifuge methods with/without air-flow. The evaluated effects include surface wetness, roughness, and pollen morphologies with/without pollenkitt. Four pollen species were investigated, and each has a unique surface morphology and pollenkitt volume. The morphology effect (size and shape of echinate/reticulate features) is a contribution by the contact area between pollen exine and surface. The pollenkitt enhances the pollen adhesion to surface; however, the detachment results indicate this nanoscale pollenkitt film (~2-8 nm thick) reduces frictional forces with air. Modeling of pollen size and contact area is used to predict pollen adhesion force.

233. Effect of interlayer slippage on the scanning tunneling microscope image of graphite

David Pullman1 dpullman@mail.sdsu.edu

Maria G Moreno-Armenta2. (1) Department of Chemistry and Biochemistry, San Diego State University, San Diego, CA 92182-1030, United States (2) Centro de Nanociencias y Nanotecnologia, Universidad Nacional Autónoma de México, Ensenada, Baja California 22800, Mexico

The origin of contrast in scanning tunneling microscope (STM) images of graphite is generally considered a solved problem; however, persistent discrepancies between experiment and theory in the shape of features have led research groups to reassess our understanding of the images. We use periodic density functional theory in conjunction with the Tersoff-Hamann formalism to simulate STM images and show that 1) lateral slippage of the top layer of graphite with respect to underlying layers can account for the elongated features often seen in experiment, and 2) the spots can be described in terms of distorted p-orbitals and in some cases pi-states located between carbon atoms. Surprisingly, small k-point meshes generally give better agreement with experiment than do large meshes. We hypothesize that the Tersoff-Hamann approximation overcounts the number of electronic states contributing to graphite's STM image, perhaps due to a selection rule that applies to the electron transfer process.

234. Bonding of anthracene derivatives to a Cu (111) surface: A combined STM and DFT study

Jonathan Wyrick1 jwyri001@ucr.edu

Yeming Zhu1, Danniel Salib2, Connor Holzke2, Ludwig Bartels2. (1) Department of Physics, University of California at Riverside, Riverside, CA 92521, United States (2) Department of Chemistry, University of California at Riverside, Riverside, CA 92521, United States

The ability to diffuse uniaxially on a Cu(111) surface has drawn attention to the substrate interactions of substituted anthracenes. We compare anthracene to three of its derivatives whose 9,10 hydrogens are replaced by the elements O, S, and Se, respectively, that act as “feet” binding the molecules to a Cu (111) substrate. DFT calculations shed light on STM imaging and diffusion studies on the three substituted species. Our theoretical work addresses the geometric and electronic structure upon adsorption, taking into account the competing effects that the “feet” have with the anthracene moiety in their interactions with the underlying Cu surface. We include vdW interactions and effects of the substrate surface state.

235. Molecular Dynamics Simulation of the atomistic structure and interfacial tension at Oil/Brine interfaces

N. Khiabani, A. Bahramian, J. L. Mendoza-Cortes, T. Pascal, A Jaramillo-Botero, M. R. Ejtehadi, P. Pourafshary, W. A. Goddard

We report molecular dynamics studies on the atomistic structure and surface tension of the interface formed between a brine solution and oil in a reservoir, with and without surfactant.. Here we consider various concentrations of NaCl in water with hexane as a prototype for the oil. We compare the predicted interfacial surface tension (IFT) from the standard Kirkwood- Buff (KB) methodology with our new 2PT approach, showing that the same results are obtained but 2PT requires only 3 nsec of MD compared to 30-100ns for KB. The 2PT method allows us to quantify the free energy, enthalpic, and entropic contributions to the IFT on a molecule by molecule basis so that we can determine the effects at the water double layer of ions and surfactants. We show that salt in the aqueous solutions increases the IFT at the water/oil interfaces, which is in turn lowered by the surfactant. Thus sodium chloride is not a surface active agent. We find that the surface layer of pure water at the interface with the oil, has a lower entropy and lower dielectric constant than the bulk water (3rd layer and beyond), while the 2nd layer has a higher entropy and higher dielectric constant than the bulk water. These properties affect the distribution of Na and Cl ions in the double layer which in turn affects the IFT leading to a remarkable difference on the hydration behavior in the bulk and in the interface. Thus we find that chloride anions dissolve more easily than sodium cations at the interface and in the bulk.

236. High temperature adsorption of Helium on ZSM-5

Hai Ching Lee hli16@aol.com

Chemistry, Aspen Systems, Inc., Marlborough, MA 01752, United States

This research utilizes two systems to probe the phenomenon of high temperature (100-600?) helium adsorption. Both methods indicate that high temperature helium adsorption on ZSM-5 proceeds 3 different phases. Under very low Helium pressure of 10-5-100 torr the weight of the sample diminishes due to exchange between helium and adsorbate of the sample. After the sample weight falls to its minimum level, an increase in helium pressure stimulates weight increase. The adsorption isotherm conforms to a log-linear function. When the continuous pressure increase reaches a specific threshold, the adsorption phenomenon changes to the Langmuir process and depending on the temperature of the sample, the processing is completed at around 10-50 torr.

237. Effect of gas type and humidity levels on the collisions of gas molecules with solid and liquid surfaces

Dongjin Seo ehdwls77@vt.edu

Dean Mastropaetro, Willam A Ducker. Department of Chemical Engineering, Virginia Tech, Blacksburg, VA 24061, United States

Lubrication forces and tangential momentum accommodation coefficients (TMACs) at atmospheric pressure were measured for different gases: helium, nitrogen, argon, and carbon dioxide. We have measured lubrication forces of these gases in a confined channel consisted of two glass surfaces, each coated with octadecyltrichlorosilane (OTS). Lubrication forces for these gases are similar, despite the differences in viscosity. This is reconciled by differences in the molecular details of collision between the solid and each gas type. The molecular details are manifest in different slip lengths and TMAC: gases with higher molar mass conserve more momentum after the collision with OTS film. Experiments with water films showed the collisions between the various gases with water conserve about the same fraction of the momentum. Thus OTS films and water films on glass behave differently. Levels of humidity dictate the amount of water films, so humidity matters in determining the lubrication force acted by gases.

238. Physical-chemical aspects of the adsorption of charged Conditioning Polymers on hair Surfaces

Gustavo S Luengo1 gluengo@rd.loreal.com

J. M. Hervet1, Colette Cazeneuve1, Nawel Baghdadli1, Carlos Drummond2, Ramon G. Rubio3. (1) L'Oréal Recherche and Innovation, Aulnay sous Bois, France (2) CRPP, Bordeaux, France (3) Universidad Complutense, Madrid, Spain

We will present an updated review of our research of the physical parameters affecting the adsorption of charged polymers on hair. A particular challenging situation is the adsorption of zwitterionic polymers. We will present results of the adsorption of succinamide fonctionalized chitosan, in the presence or not of surfactants on a model surface for bleached hair. The polymer adsorbs 35-45% less in a neutral ionic state (PZ) than in a cationic state (PC). This slightest adsorption of the neutral polymer is at the originof the higher fiction of hair and therefore a lack of smoothness and disentangling capacity. The deposition of the neutral polymer PZ in aqueous solution with 2 types of surfactants is around 60-65% lower than the PC in presence of surfactants. We concluded that the electrostatic interactions between the surface and the deposition are not only the possible interactions playing in this case.

239. Titanium alkoxide-ethylene glycol mixed precursors for coating TiO2 on nanoparticles

Michael Dahl mdahl001@ucr.edu

Yadong Yin. Department of Chemistry, University of California, Riverside, Riverside, California 92521, United States

The coating of TiO2 shells onto sub-micron sized particles has been widely studied in recent years with much success occurring in the coating of templates with sizes above 50 nm. Direct coating on particles below this size has been difficult to attain especially with good control over properties such as thickness and TiO2 crystallinity. Here we demonstrate a mixed solution of titanium n-butoxide and ethylene glycol to create a titanium-glycolate coating on aqueous nanoparticles. This coating can subsequently be crystallized into TiO2 through refluxing in water or calcination. Direct coatings on metal nanoparticles such as gold and silver can be easily achieved with a corresponding shift in the surface plasmon resonance. Additionally, coatings on larger microspheres, e.g. SiO2 and polymer spheres, can be done through a simple extension of this method.

240. Anisometric supraparticlesfrom colloidal building blocks by an evaporation method

Michael Gradzielski1 michael.gradzielski@tu-berlin.de

Marcel Sperling1, Orlin Velev2. (1) Institut fuer Chemie, Stranski-Laboratorium, Technische Universitaet Berlin, Berlin, Germany (2) Department of Chemical and Biomolecular Engineering, North Carolina State University, United States

Supraparticles made by self-assembly of colloids offer high potential in terms of controlling structure, shape and functionality in complex colloidal systems. Their properties are determined by the constituting colloidal building blocks that can impart special functionality to them, like catalytic, optical, magnetic properties, etc., opening interesting perspectives for a variety of applications. In our experiments we employed the evaporation method and fumed silica as main colloidal building block. For this system the shape of the finally formed dry supraparticles depends strongly on the ionic strength of the aqueous solution. For low ionic strength circular symmetric particles are formed while beyond a critical salt concentration anisometric, boat-like structures are observed, where the average anisometry depends in a systematic fashion on the ionic strength. This simple way of shape control can also be extended to form hybrid supraparticles containing for instance catalytically active metal colloids, magnetic nanoaparticels, or fluorescent latices.

241. Formation of amphiphilic molecular capsule through dynamic self-assembly process

Toshiaki Taira1 t-taira@aist.go.jp

Dariush Ajami2, Julius Rebek, Jr.2. (1) Research Institute for Innovation in Sustainable Chemistry, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8565, Japan (2) The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, California 92037, United States

Self-assembled capsules are reversibly formed assemblies which can surround their guests and isolate them from the bulk solution. Here we report dynamic formation of molecular capsule 1.24.1 composed of two bowl-shaped molecules 1 and four grycolurils 2 . In solution, 1.24.1 provides an amphiphilic environment with hydrophobic aromatic ends and hydrophilic glycoluril belt at the center and we found that 1.24.1 encapsulates both hydrophobic and hydrophobic guests in its inner space.

242. Synthesis and characterization of environmentally benign nanoparticles

Alexander P Richter1 aprichte@ncsu.edu

Joseph Brown1, Vesselin N Paunov2, Simeon Stoyanov3, Sumit Gangwal4, Elaine A. Cohen Hubal4, Orlin D. Velev1. (1) Department of Chemical and Biomolecular Engineering, North Carolina State Univeristy, Raleigh, NC 27606, United States (2) Department of Chemistry, University of Hull, Hull, United Kingdom (3) Laboratory of Physical Chemistry and Colloid Science, University of Wageningen, Wageningen, The Netherlands (4) National Center for Computational Toxicology, US EPA, RTP, NC 27711, United States

There has been a growing interest in replacing current non-biodegradable nanosystems with environmentally benign biopolymer based ones to minimize post-utilization hazards due to persistent nanomaterial waste. Lignin-based nanoparticles (NPs) are biodegradable, environmentally benign, and may be potentially employed as foam and emulsion stabilizers, as drug delivery system, and as matrices for environmental remediation systems. We will report means of synthesizing such Environmentally benign Nanoparticles (EbNPs) in a simple, inexpensive, and non-toxic way. We used Indulin AT (IAT) lignin and applied environmentally friendly acid precipitation technology for EbNP synthesis. By utilizing the ethylene glycol (EG)-water based pH drop method we were able to obtain IAT EbNPs with increased pH stability ranging from pH 4.0 to 9.0. We hypothesize that the pH stability of these EbNPs is due to a favorable molecular stacking facilitated by EG prior to precipitation. Post-synthesis treatment options for fabrication of antimicrobial suspensions have been explored and formulated.

243. Perovskite Oxide Nanocrystals: Room Temperature Synthesis and Crystal Structure

Federico Rabuffetti rabuffet@usc.edu

Richard Brutchey. Department of Chemistry, University of Southern California, Los Angeles, CA 90089, United States

Alkaline-earth perovskite oxide nanocrystals with the formula ABO3(A = Sr, Ba; B = Ti, Zr) and their corresponding solid solutions exhibit a wide range of properties that make them promising functional materials in the areas of energy conversion and storage, display technologies, and heterogeneous catalysis. Our group has developed a novel vapor diffusion sol-gel approach to the synthesis of perovskite oxide nanocrystals under ultrabenign conditions (atmospheric pressure, low temperature, and near neutral pH). This method affords the preparation of complex perovskite sub-30 nm Ba1-xSrxTi1-yZryO3 (0 = x = 1, 0 = y = 1) nanocrystals of arbitrary and well-defined stoichiometry. A comprehensive structural picture of perovskite oxide nanocrystals was achieved using a dual space approach combining Rietveld and pair distribution function analysis of X-ray scattering data. This methodology allowed for a fundamental understanding of the effect of spatial confinement on dipole-dipole cooperative interactions that are the structural basis for ferroelectricity.

244. Bioinspired Hybrid Materials by Gluing of Anisotropic V2O5 Nanoparticles

Ulrich Tritschler1 ulrich.tritschler@uni-konstanz.de

Igor Zlotnikov2, Paul Zaslansky3, Peter Fratzl2, Helmut Schlaad4, Helmut Cölfen1. (1) Department of Chemistry/Physical Chemistry, University of Konstanz, Konstanz, Germany (2) Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Potsdam, Germany (3) Julius Wolff Institute and Centre for Musculoskeletal Surgery, Charité - Universitätsmedizin Berlin, Berlin, Germany (4) Department of Colloid Chemistry, Max Planck Institute of Colloids and Interfaces, Potsdam, Germany

Natural organic-inorganic composites are built of stiff and brittle mineral crystals in a matrix of soft and ductile organic materials. Due to a sophisticated hierarchical structuring and a well-controlled coupling at the interface between the two components, these biominerals combine both stiffness and toughness. Herein, biomimetic composite structures were transferred to the synthetic realm by gluing together vanadium pentoxide nanoparticles with polymers. Composite materials with structuring on two hierarchical levels were produced through liquid crystal (LC) formation of polymer and inorganic nanoparticles: alignment of anisotropic nanoparticles (first level) within a structured organic matrix (second level). The polymers used for synthesizing organic-inorganic composite materials are copolymers with pendant cholesteryl units, enabling the polymer to form lyotropic phases, and carboxyl units, binding ('gluing') selectively to nanoparticle faces. Different analytical techniques revealed a shear-induced hierarchical structuring of vanadium pentoxide composites from the micrometer to the nanometer lengthscale, resembling the structures of Biominerals.

245. Effect of surface charge segulation on the transport in fluidic nanochannels

Dimiter N. Petsev1 ulrich.tritschler@uni-konstanz.de

Mark Fleharty1, Frank van Swol2. (1) Department of Chemical and Nuclear Engineering, University of New Mexico, Albuquerque, New Mexico 87131, United States (2) Sandia National Laboratories, Albuquerque, New Mexico 87185, United States

We examine the effect of surface charge regulation at the wall of a fluidic nanochannel on the transport of current and fluid. It is shown that for small channels with overlapping electric double layer the apparent electrokinetic zeta potential is no longer a property that depends only on the material of the wall and the type of electrolyte solution. Instead it is also a strong function of the channel width. In addition to that the surface (or the zeta) potential strongly depends on the pH of the solution. This means that the overall performance of a nanochannel will depend on a complex interplay between channel width, salt concentration and (separately) the concentration of hydrogen and hydroxyl ions in the solution. A detailed analysis of the effect of these parameters is presented.

246. Characterization of a silica surface modified with an antimicrobial Moringa protein

Toni M Bechtel1 tmb5235@psu.edu

Darrell Velegol1, John Riley2, Robert D. Tilton2, Stephanie B Velegol3. (1) Department of Chemical Engineering, The Pennsylvania State University, University Park, PA 16802, United States (2) Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, United States (3) Department of Civil and Environmental Engineering, The Pennsylvania State University, University Park, PA 16802, United States

The seeds of the Moringa oleifera tree contain a cationic protein (MOCP) that works as an antimicrobial flocculent in water. We have shown that this protein adsorbs from a solution of crushed Moringa oleifera seeds to a silica surface. This functionalized silica was shown to remove turbidity and inactivate E. coli in water. Our current work focuses on characterizing MOCP-modified silica surfaces. We measured the surface excess concentration via ellipsometry and changes in zeta potential via Zeta Spin. These results indicate that the amount of adsorbed protein and the adsorption reversibility are highly dependent on the adsorbed layer history and ionic strength. In addition we discuss how the surface characteristics change when the MOCP is adsorbed from de-fatted seeds. This work aims toward the development of a low-cost, sustainable, antimicrobial surface for water treatment in the developing world.

247. Transport of fluid and particles into-and-out of dead end pores

Abhishek Kar1 ayk5241@psu.edu

Tso-Yi Chiang1, Isamar Ortiz Rivera2, Ayusman Sen2, Darrell Velegol1. (1) Department of Chemical Engineering, Penn State University, University Park, Pennsylvania 16802, United States (2) Department of Chemistry, Penn State University, University Park, Pennsylvania 16802, United States

Achieving transport inside dead end pores is not currently possible with pressure driven mechanisms, which limits our ability to obtain material from these pores, or to put material into them. Here we show that the phenomenon of diffusioosmosis can be used to drive flows in dead end pores, and the flows can be used to sweep otherwise-trapped materials from the pore into a sink, or vice versa. These flows arise along the walls of the channel due to an imposed or self-generated salt gradient. We observe that tracer particles have a finite axial speed of roughly 10 microns/s, as well as a finite crosswise transport. Using electrokinetic modeling along with independently measured system parameters, we find solid agreement between predicted speeds and our experimental data. The temporal nature of the salt gradients may explain some of the other phenomena like the LoSal waterflooding process and DNA translocation in solid-state nanopores.

248. Attachment efficiency of TiO2 nanoparticles in sand under low seepage velocity

Seunghak Lee1 seunglee@kist.re.kr

Eunhyea Chung2. (1) Center for Water Resource Cycle, Korea Institute of Science and Technology, Seoul, Republic of Korea (2) Department of Energy Resource Engineering, Seoul National University, Seoul, Republic of Korea

Several studies have shown that a decreases as the seepage velocity increases. However, this relationship might not be readily applicable for colloid transport in the subsurface because the velocities considered in previous studies are orders of higher than typical groundwater velocity. Lower value of groundwater velocity implies that the hydrodynamic force applied to nanoparticles might not be high enough to cause any movement of colloids from the deposition well. Thus, the relationship between a and seepage velocities in lower ranges could be quite different from the earlier findings in higher ranges. In this study, sand column tests were performed by varying the seepage velocity in the ranges relevant to groundwater flow under unfavorable condition with surrogate of natural organic matter. Results show that a increases with the seepage velocity, which is opposite to the relationship previously reported.

249. Titanium Dioxide Nanoparticle Removal: Role of Solution Chemistry, Natural Organic Matter, Coating, and Source Water

Ryan Honda rhond001@ucr.edu

Sharon Walker. Department of Chemical and Environmental Engineering, University of California, Riverside, Riverside, CA 92521, United States

Titanium dioxide nanoparticles (TNP) have been found in wastewater effluent and have the capacity to enter ground and surface waters. Thus, research is needed on how to effectively remove them in water treatment. Traditional separation methods include coagulation, flocculation, and sedimentation (CFS). This study involves investigating TNP removal using aluminum sulfate as a coagulant in KCl and two model source waters during CFS. Absorbance values were recorded at each CFS stage to determine total particle removal. Extensive characterization of hydrodynamic diameter and zeta potential has been done. The role of coagulant dose, coating (bare and coated), presence of natural organic matter, and solution chemistry has also been tested. To date, aggregate size and zeta potential have been found to directly correlate to total removal after CFS. The governing mechanisms involved in TNP aggregation and removal under various solution chemistries will be discussed.

250. Transport behavior of nanoparticles, aqueous solutions in porous media vs. T

Mason B. Tomson mtomson@rice.edu

Lu Wang, Amy T. Kan. Department of Civil and Environmental Engineering, Rice University, Houston, Texas 77005, United States

The revolution of nanotechnology has led to the increased application of nanoparticles in many industrial fields, water treatment, oil and gas, and remediation, to mention a few. Nanoparticles, due to their small size transport through subsurface formations without changing the pore structure and thus have received tremendous attention as delivery tools and as probes. When released into the environment, nanoparticles tend to form large aggregates. The size of the aggregate determines the mobility, stability and reactivity of nanoparticles in the environment. Nanoparticles, about 100 nm and less can be functionalized with ionic and non-ionic polymers that change interaction with temperature. A modified DLVO theory has been developed that includes both steric and electrostatic effects and this has been used in classic filtration theory to model the breakthrough of nanoparticles from packed cores. Examples of the success of this new model will be illustrated.

251. Microcapsules from double emulsions: Control of capsule morphology and release kinetics

Abiola Shitta1 ashitta3@gatech.edu

Helmut Auweter2, Wen Xu3, Sven H Behrens1. (1) School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0100, United States (2) BASF SE, Limburgerhof, Germany (3) BASF Corporation, Research Triangle Park, NC 27709, United States

Double emulsion droplets are useful precursors for microcapsules with functions in the storage, transport, and controlled release of pharmaceuticals and other active cargoes. Application properties of such microcapsules crucially depend on the morphology of the templating emulsion droplets. Exquisite control in this matter can be achieved using microfluidics-based, droplet-by-droplet fabrication of “designer” emulsions, but the production rates are severely limited, and thus many high volume applications continue to rely on classical emulsification techniques. In this presentation we will discuss strategies to control droplet morphology that can be applied in standard batch emulsification. We will show that some of the common limitations of batch emulsification can be overcome. The achievable control over (double) emulsion droplets and the consequences for droplet-based microcapsules will be illustrated using a model system with relevance to field of active formulation.

252. Bottom-up nanoemulsification of hydrocarbons in water from hydrothermal homogeneous solutions

Shigeru Deguchi shigeru.deguchi@jamstec.go.jp

Nao Ifuku. Institute of Biogeosciences, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Kanagawa 237-0061, Japan

Oil and water do not mix, but they do mix freely near the gas/liquid critical point of water (Tc = 374 C, Pc = 22.1 MPa). We used the unique phase behavior of oil/water mixtures at extreme conditions and developed a novel bottom-up nanoemulsification method that we call MAGIQ (Monodisperse nAnodroplet Generation in Quenched hydrothermal solution). A flow type instrument was developed and experiments were carried out using a model system consisting of dodecane, water, and Brij 97. Homogeneous solutions of dodecane in water were prepared at high temperature and high pressure, and rapidly cooled at a rate of 200–240 C/sec down to room temperature to induce phase separation. We found that spinodal decomposition of the solution resulted in bottom-up formation of monodisperse nanodroplets (down to 53 nm in diameter) of dodecane in water. The flow-type instrument minimized thermal decomposition of dodecane to less than 1%.

253. Interfacial shear Rheology of crude oil-water interface: Impact of aqueous phase ionic strength and composition on interfacial elasticity

Mehrnoosh Moradi mmoradib@uwyo.edu

Vladimir Alvarado. Department of Chemical and Petroleum Engineering, University of Wyoming, Laramie, WY 82071, United States

Emulsions stability has been attributed to the formation of networks of viscoelastic, cross-linked compounds indigenous to crude oil. The attachment of asphaltenes to the interface has been hypothesized to increase interfacial elasticity, which impart mechanical strength to the interface and increases emulsion stability. The objective of this work is to investigate the impact of interfacial viscoelastic property on the stability of emulsions by using double-wall ring geometry. The interfacial dynamic moduli are measured in the linear viscoelastic region. The effect of aqueous phase ionic strength and composition is investigated. Additionally, the time evolution of interfacial moduli is studied to evaluate the kinetics of adsorption of polar materials. Earlier work has shown that lower ionic strength, particularly in the present of calcium, is conducive to higher emulsion stability. Results demonstrate the kinetic rate of film formation and confirm that lower salinity favors the formation of a more elastic film.

254. Stability analysis of microdrop shrinkage during concentrating processes

Janet A. W. Elliott janet.elliott@ualberta.ca

Fatemeh Eslami Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 2V4, Canada
Concentrating of solutes and nanoparticles within aqueous microdrops has many applications in biological and microfluidic systems. Using an organic phase in which water has a small solubility, provides a mean for the solutes within aqueous microdrops to be concentrated via water molecules leaving the drop and dissolving in the organic phase. We had previously investigated this concentration process thermodynamically. Considering two kinds of solutes from the solubility limit point of view, descriptions were provided for the equilibrium system behaviour including microdroplet final concentration and final size.1 In the current work, by means of free energy analysis we describe the different stability status of the equilibrium states for the microdrop concentration process, and the influence of initial drop size and amount of organic phase on this stability analysis has been studied. 1F. Eslami, J. A. W. Elliott, “Design of microdrop concentrating processes”, J. Physical Chemistry B, In Press.

255. Gravity driven advective motion during sessile drops merging on a surface

Stephen Garoff1 sg2e@andrew.cmu.edu

Ying Zhang1, Samuel Oberdick1, Shelley L Anna2,3. (1) Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, United States (2) Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, United States (3) Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, United States

We study the mixing behavior of two sessile drops following the coalescence on a silicone elastomer surface with contact angle of about 90. The two drops are of equal volumes at coalescence, but different densities and viscosities. Using Laser induced fluorescence technique, we obtain both a top view of the contact line motion and a side view of the cross-sectional flow. The initial meniscus bridge healing occurs at the short inertio-capillary time scale. However, the interface between the dyed and undyed components remains sharp, with diffusive mixing occurring at much longer timescales. At intermediate time scales the motion is controlled by a gravity current, which leads to the eventual stratification into two separate layers within the composite drop. Using lubrication analysis, we characterize the gravity current as a function of the drop sizes, density and viscosity differences. The numerical results capture the interface movement due to the gravity driven flow.

256. Thin film drainage between micro- drops and bubbles under applied cyclical drives to mimic micro-fluidic pumping scenarios

Raymond Dagastine1 rrd@unimelb.edu.au

Rico Tabor4, Chu Wu3, Franz Grieser2, Derek Chan3. (1) Department of Chemical and Biomolecular Engineering, The University of Melbourne, Parkville, Victoria 3010, Australia (2) School of Chemistry, The University of Melbourne, Parkvillle, Victoria 3010, Australia (3) Department of Mathematics and Statistics, The University of Melbourne, Parkvillle, Victoria 3010, Australia (4) School of Chemistry, Monash University, Clayton, Vic 3800, Australia

This talk will focus on what we can learn from the direct force measurement of sequential collisions of pairs of micro-drops or micro-bubbles in order to mimic pumping conditions in micro-fluidic devices(1). A number of diverse velocity drive profiles were used to drive to drops together with repeated collisions including waveforms for sinusoidal, peristaltic and diaphragm pumping using AFM. In most cases, it was shown that when equilibrium interactions of the drops were in a meta-stable state, small perturbations in pumping conditions could cause drop coalescence. This was further probed through using simple constant velocity approach and retract cycles where the approach and retract velocities were varied independently. Agreement between quantitative modeling of these collisions and the experimental measurements allows for visualization of the thin film and pressure profiles during these processes. 1. Tabor, Wu, Grieser, Chan, Dagastine, Soft Matter, 2013 , 9, 2426-2433.

257. Protein conformational flexibility as a prerequisite for the formation of crystalline nuclei

Peter G. Vekilov1,2 vekilov@uh.edu

Maria Vorontsova1, Weichun Pan1, Vassiliy Lubchenko2. (1) Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States (2) Department of Chemistry, University of Houston, Houston, Texas 77204, United States

Nuclei of ordered solid phases of proteins in native conformations form within crucial precursors, which are metastable mesoscopic liquid clusters, existing both in the homogenous region of the solution phase diagram and in the region supersaturated with respect to an ordered solid phase. We show that the cluster exist due to the conformation flexibility of the protein molecules, leading to the exposure of hydrophobic surfaces and enhanced intermolecular binding. We show that additives known to destabilize the native protein structure lead to enhanced cluster formation. NMR characterization reveals that in solutions, in which clusters are present at concentrations allowing each protein molecule pass through a cluster within an hour, the protein conformational variability is significantly enhanced in comparison to solutions without clusters. These results indicate that protein conformational flexibility might be the mechanism behind the metastable mesoscopic complexes and, hence, behind the clusters and new-phase nucleation.

258. Biophysical studies on the structural adaptation of porcine amelogenin in micelles and vesicles

Karthik Balakrishna Chandrababu karthiba@usc.edu

Sowmya Bekshe Lokappa, Janet Moradian-Oldak. Center for Craniofacial Molecular Biology, University of Southern California, Los Angeles, California 90033, United States

Amelogenin, an intrinsically disordered protein, is the major component in the developing dental enamel matrix. The supramolecular structure formed by its self assembly is considered to be important for the formation of highly ordered enamel crystal arrays. The recombinant porcine amelogenin (rP172) was proved to be highly flexible with several short structural regions and it was predicted that the flexible and structured regions should cooperatively help amelogenin during biomineralization. In order to gain more insights into the possible conformational transitions of amelogenin during mineralization we investigated the structural adaptability rP172 in the presence of micelles and vesicles and analyzed the transformation between its disordered to ordered conformations. Our final results revealed that rP172 penetrates into hydrophobic core of anionic liposomes and SDS micelles and coils to form helix. Our comprehensive analysis of amelogenin interactions with membrane models can provide detailed insight into mechanisms of amelogenin-cell or amelogenin-vesicle interactions during amelogenesis.

259. Forces between micro-bubbles in the presence of novel responsive peptide surfactants

Raymond Dagastine rrd@unimelb.edu.au

Department of Chemical and Biomolecular Engineering, The University of Melbourne, Parkvillle, VIC 3010, Australia

Reversibly switchable surfactants are becoming increasingly important for controlling foam stability in many industrial applications because they can be recycled as foaming and antifoaming agents. Novel stimuli responsive peptide surfactants have been previously studied to classify the molecular confirmation at the air-water interface before and after switching. In this study, Atomic Force Microscopy (AFM) was used to correlate the peptide conformation to directly measured changes in colloidal interaction forces between immobilized air bubbles before and after switching(1). Results were compared to previous studies of macroscopic foam column stability using these peptides. Differences in foam stability and the AFM force measurements were apparent, highlighting variations in directly measured equilibrium colloidal interactions to macroscopic bulk behavior. These results help elucidate the connection between the switching mechanism of novel stimuli responsive peptide surfactants and their effect on colloidal scale interactions between bubbles. 1. Balasuriya, Dagastine, Langmuir 2012, 28, 17230.

260. In-situ multi-photon microscopy characterization of the effect of ionic strength on collagen fiber formation within hydrogels

Xuye Lang2 xlang001@ucr.edu

Julia Lyubovitsky1,2. (1) Bioengineering, UC Riverside, Riverside, CA 92521, United States (2) Biochemistry, UC Riverside, Riverside, CA 92521, United States

The complex supramolecular architecture of collagen biopolymer plays an important role in the applications of this biomaterial. Studying nucleation, assembly and 3-D arrangement of collagen fibers can accelerate rational design of collagen-based biomedical products. Optical density measurements and novel characterization with multi-photon microscopy (MPM) were carried out in-situ during polymerization of collagen hydrogels. Hydrogels were separately prepared at room temperature and 27 °C while varying ionic strength of phosphate buffer with 0 to 0.9 M NaCl. Assembly depends greatly on the polymerization temperature and collagen solid content. Optical density measurements showed no obvious effect when NaCl was between 0.15 and 0.6 M and MPM detected long collagen fibers. Short lag time and fast assembly rates were observed when NaCl was 0 or 0.9 M. Short, connected fibers were detected under 0 M NaCl. In 0.9 M NaCl, only unconnected one micron fiber nuclei with low second harmonic generation contrast formed.

261. Integration of alpha helical peptides to lipid-polymer microbubbles

Joseph V Badami jbadami@che.ccny.cuny.edu

Raymond S Tu. Chemical Engineering, The City College of New York, New York, New York 10031, United States

The ability to direct therapeutic and visualization agents to specific locations within a biological system has become an attractive approach to drug delivery with a potential upside of limiting cytotoxic effects to uncorrupted regions. Microbubbles comprise one distinct set of “theranostic”, biomimetic assemblies that provide an effective means for both delivery and imaging when used in conjunction with clinical ultrasound. In such particles however, the lateral interactions amongst molecular constituents at the gas/liquid interface impacts overall system properties, including size, stability, and mechanics. We have designed a set of amphiphilic peptides that can partition into the microbubble interface, where we influence phase behavior by controlling charge distribution along the z-axis of the helical cylinder. This work investigates the effect of these rationally designed peptides on bubble size distribution and stability. We aim to quantify the influence of charge distribution on lateral phase behavior, interfacial structure, and bubble mechanics.

262. Ice Release Coatings

Di Gao gaod@pitt.edu

University of Pittsburgh, United States

Icing in a cold environment causes many problems, including glazing rotors and blades of wind turbines, breaking power lines, and stalling airfoil of aircrafts. Most of these problems are due to build-up of ice on surfaces. One promising method to prevent ice build-up is to protect the surface with a coating that has an ultra-low ice adhesion strength (i.e. ice barely adheres to the coating), so that ice formed on such a coating can be released by the weight of ice alone or by a very small shear force applied to the ice. This talk presents recent advances in making coatings that possess ultralow ice adhesion strength (i) by tuning the surface texture and (ii) by continuously releasing a lubricant from the coating surface, as well as commercialization progress of these coatings for industrial applications.

263. Which Controls Wetting? Contact Line versus Interfacial Area: Simple Experiments on Capillary Rise

C. W. Extrand chuck_extrand@entegris.com

Sung In Moon. Surface Science R&D, Entegris, Chaska, MN 55318, United States

Working equations that describe wetting phenomena can be derived in a variety of ways, by starting from capillary forces, Laplace pressure, or solid surface energies. We examined the relative importance of the contact line and interfacial areas in the capillary rise inside small diameter glass tubes. A series of simple experiments demonstrate that this wetting phenomenon is controlled by interactions in the vicinity of the contact line.

264. How superhydrophobicity breaks down

Periklis Papadopoulos papadopoulos@mpip-mainz.mpg.de

Lena Mammen, Xu Deng, Doris Vollmer, Hans-Jürgen Butt. Max Planck Institute for Polymer Research, Mainz, Germany

Drops are repelled by superhydrophobic surfaces, because air is trapped under them (Cassie state). In applications the collapse of the Cassie state must be prevented. Here, confocal microscopy images the water–air interface on superhydrophobic micropillars (Papadopoulos et al., PNAS 2013, DOI:10.1073/pnas.1218673110) or fractal silica (Deng et al., Science, 335 , 6064 (2012)). Once the capillary pressure is high enough the Cassie state collapses. Depending on geometry the drop sags into the substrate or slides along the walls of the pillars.

265. Dynamic defrosting via spontaneous dewetting on nanostructured superhydrophobic surfaces

Jonathan B. Boreyko boreykojb@ornl.gov

Bernadeta R. Srijanto, Trung Dac Nguyen, Miguel Fuentes-Cabrera, C. Patrick Collier. Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6493, United States

Nanostructured superhydrophobic surfaces enable jumping-drop condensation that continuously removes moisture from the surface. We demonstrate that the jumping-drop effect can be exploited to passively remove subcooled condensate from a subzero superhydrophobic surface before heterogeneous ice nucleation can occur. However, the condensing surface still frosts over eventually due to the invasion of an inter-drop freezing front that propagates from neighboring surface defects. It is therefore crucial to determine whether facile defrosting is possible on a superhydrophobic surface. We show that when a film of frost on a nanostructured superhydrophobic surface is partially melted into a slush puddle composed of water and ice, it is able to spontaneously dewet into mobile Cassie drops that slide off the surface at low tilt angles. This dynamic defrosting effect is driven by the spontaneous dewetting of the slush puddle to the shape corresponding to its equilibrium surface energy on the superhydrophobic surface.

266. Polymeric coatings for ultra-low ice adhesion

Kevin B Golovin kegolo@umich.edu

Anish Tuteja. Department of Materials Science & Engineering, University of Michigan, Ann Arbor, MI 48103, United States

The ability of a surface to easily shed ice offers enormous advantages for power lines, airplane wings, wind turbine blades and sub-freezing environment naval components. In this work we develop polymer coatings that are able to shed ice with nearly no additional force beyond friction. The coatings can be applied in a single-step, using a spray-based methodology, on nearly any surface and over large areas. After multiple icing – deicing cycles, our icephobic coatings still show an adhesive strength comparable to the best values reported in the literature (~ 10 kPa). We also optimize the coating – ice interface to minimize the adhesive strength. Our analysis of force vs. time curves allows us to explain the phenomenon using simple frictional arguments. Further, we evaluate the resistance of the coating to multiple successive icing – deicing cycles, temperature cycling and actual winter storm conditions.

266. Polymeric coatings for ultra-low ice adhesion

Kevin B Golovin kegolo@umich.edu

Anish Tuteja. Department of Materials Science & Engineering, University of Michigan, Ann Arbor, MI 48103, United States

The ability of a surface to easily shed ice offers enormous advantages for power lines, airplane wings, wind turbine blades and sub-freezing environment naval components. In this work we develop polymer coatings that are able to shed ice with nearly no additional force beyond friction. The coatings can be applied in a single-step, using a spray-based methodology, on nearly any surface and over large areas. After multiple icing – deicing cycles, our icephobic coatings still show an adhesive strength comparable to the best values reported in the literature (~ 10 kPa). We also optimize the coating – ice interface to minimize the adhesive strength. Our analysis of force vs. time curves allows us to explain the phenomenon using simple frictional arguments. Further, we evaluate the resistance of the coating to multiple successive icing – deicing cycles, temperature cycling and actual winter storm conditions.

267. Molecular Model for the Thermodynamic Stability of Virus

Jehoon Kim1 jkim194@ucr.edu

Roya Zandi2, Jianzhong Wu1. (1) Department of Chemical & Environmental Engineering, UC Riverside, Riverside, California 92521, United States (2) Department of Physics and Astronomy, UC Riverside, Riverside, California 92521, United States

We report a thermodynamic model for the stability of viral particles. For the Hepatitis B virus (HBV), an effective coarse-grained model is constructed, which includes all pertinent molecular interactions: the hydrophobic association of capsid subunits, the electrostatic interactions, the entropy and the excluded volume effects. Based on such an explicit framework, we investigate the stability of the viral particle with a focus on physiological cellular conditions. We consider the free energy of the empty capsid formation and the interaction free energy of pre-genomic RNA and C-terminal domain (CTD) of the capsid proteins. In comparison with experimental investigations, our model presents appropriate equilibrium values for the capsid assembly and reveals new insights on the contribution of hydrophobic association to the capsid assembly. In addition, our model describes the balanced electrostatic interaction between capsid proteins and genome as well as the effects of temperature and ion concentration for the capsid stability.

268. Controlled liposome fusion mediated by lipidated coiled-coil peptides

Alexander Kros a.kros@chem.leidenuniv.nl

Dept. of Soft Matter Chemistry, Leiden Institute of Chemistry, Leiden University, Leiden, - 2300RA, The Netherlands

Membrane fusion is essential for the delivery of chemicals across biological barriers to specific cellular locations controlled by SNARE-proteins. To allow membrane fusion to be better understood we have mimicked this process with a bottom-up model in which synthetic fusogens (i.e. lipidated coiled-coil peptides) replicate the essential features of this process. We discuss how liposome fusion is controlled by different parameters within this modelsystem. The lipopeptide fusogens form specific coiled-coils that dock liposomes together, resulting in the merging of membranes via the stalk intermediate. Unusually for model systems, the lipopeptides can rapidly lead to fusion of entire liposome populations and the liposomes can undergo many rounds of fusion. The rate and extent of fusion and the number of fusion rounds can be manipulated by adjusting the fusogen and liposome concentrations. The improved understanding of membrane fusion paves the way for controlled liposome mixing towards nanoreactors.

269. Nanometer range liposome synthesis via hydration in packed beds

Sundar S.K. sundar.bio@gmail.com

Mahesh Tirumkudulu. Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, Maharashtra 400076, India

Drug delivery using liposomes targeting the afflicted areas of the host with minimal drug loss has attracted significant interest in the scientific community. While traditional liposome preparation techniques result in polydisperse suspension, liposomes prepared via microfluidic approach give monodisperse suspension with tightly controlled sizes. Here, we describe a technique to synthesize monodisperse liposomes in the sub-50 nm range with low polydispersity by drying lipids dispersed in an organic solvent in a packed bed of colloidal particles followed by hydration using aqueous medium. The volume fraction of the liposomes can be varied by changing the ratio of lipid to buffer volume. Our experiments suggest that the size of the liposome is controlled by the surface topography of the colloidal particle rather than by the pore size. We conclude with a discussion on the possible mechanisms for liposome formation along with the potential for commercialization of the above technique.

270. Entrapment of integral membrane proteins in nanoporous silica gels via nanolipoprotein particles

Wade F Zeno1 wzeno@ucdavis.edu

Mahesh Tirumkudulu. Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, Maharashtra 400076, India

Marjorie L Longo1, Subhash H Risbud1, Matthew A Coleman2. (1) Chemical Engineering and Materials Science, University of California, Davis, Davis, California 95616, United States (2) Lawrence Livermore National Laboratory, Livermore, California 94550, United States

270. Entrapment of integral membrane proteins in nanoporous silica gels via nanolipoprotein particles

Wade F Zeno1 wzeno@ucdavis.edu

Marjorie L Longo1, Subhash H Risbud1, Matthew A Coleman2. (1) Chemical Engineering and Materials Science, University of California, Davis, Davis, California 95616, United States (2) Lawrence Livermore National Laboratory, Livermore, California 94550, United States

Immobilization of integral membrane proteins (IMPs) in transparent, nanoporous silica gels has proven to be a challenge, as current and previous techniques utilize liposomes as biological membrane hosts. The instability of liposomes in nanoporous gels is attributed by their size (~150 nm) and altered structure and lipid dynamics upon entrapment, ultimately resulting in disruption of protein activity. We intend to address these issues by using nanolipoprotein particles (NLPs) as biomembrane hosts. NLPs are discoidal patches of lipid bilayer that are belted by apolipoproteins (~5 nm thickness and 10-30 nm diameter). The IMP-NLP complexes are synthesized in a cell-free environment, which circumvents traditional protein reconstitution in membranes. Bacteriorhodopsin - a robust IMP protein that indicates its proper conformation via distinct purple coloration – will serve as a model IMP for this system. In addition to the phase behavior of the lipids, spectral and physical properties of bacteriorhodopsin will be examined.

271. Molecular modeling approaches for self-assemblyprocesses of amphiphilic compounds and their interaction with carbon nanoparticles

Arben Jusufi arben.jusufi@csi.cuny.edu

Department of Chemistry, City University of New York - College of Staten Island, New York, NY 10314, United States

Molecular simulations of self-assembly phenomena of amphiphilic molecules is a challenging task due to the long time scales (>1µs) needed for aggregation, and the low critical association concentrations (cac) that typically lie way below 10mM. Hence, the development of creative modeling and methodologies becomes essential. We discuss approaches that range from implicit to explicit solvent coarse-grained (CG) models of surfactants and lipids that allow the study of self-association properties such as the aggregate size and cac. As an application, a recent CG-MD simulation study on the interaction of carbon nanoparticles with lipid membranes is discussed. We present results of the free energy change when C60, C180, and C540 fullerenes are transferred from bulk water to the interior of a dioleoylphosphatidylcholine bilayer where fullerene-clusters are formed. While C60-clusters do not distort membrane morphology we found that C540-clusters cause substantial membrane undulations with potential implications for cytotoxicity of biological cells.

272. Tunable nano-patterns from polymer brushes: Molecular dynamics simulations

Thomas Lee1 thomas.lee@sydney.edu.au

Chiara Neto1, Shaun Hendy3,2. (1) School of Chemistry, The University of Sydney, Sydney, NSW 2006, Australia (2) MacDiarmid Institute for Advanced Materials and Nanotechnology, Victoria University of Wellington, Wellington, New Zealand (3) Callaghan Innovation, Lower Hutt, New Zealand

Under poor solvent conditions polymer brushes may collapse into nano-patterned layers, with various possible morphologies including those shown in Figure 1. We have studied this process, known as constrained dewetting, using molecular dynamics simulations. We have shown that the nano-pattern morphology can be tuned by the adsorption of a small amount of good solvent into the brush, and examined the potential of polymer brushes as surfaces with switchable fluid-flow boundary conditions, and as templates for controlling nucleation at surfaces.

273. Aerosol Particles from Southern Finland, Amazonia, and California Studied by Vibrational Sum Frequency Generation

Franz Geiger geigerf@chem.northwestern.edu

Chemistry, Northwestern U, Evanston, IL 60202, United States

This talk summarizes our current state of knowledge regarding the analysis of synthetic and natural aerosol particles from forest and marine environments by vibrational sum frequency generation. We describe how the combination of multiple disciplines, such as aerosol science, advanced vibrational spectroscopy, meteorology, and chemistry can be highly informative when studying particles collected during atmospheric chemistry intensives, such as those carried out during HUMPPA-COPEC-2010, AMAZE-08, BEARPEX-2009, or CAICE 2011 and when they are compared to results from synthetic model systems such as particles from the Harvard Environmental Chamber (HEC). Discussions regarding the future of the chemical analysis of aerosol particles are given in the context of providing a path toward detailed spectroscopic assignments of SOA particle precursors and constituents and to fast-forward, in terms of mechanistic studies, through the SOA particle formation process.

274. Secondary Organic Aerosol Formation from Naphthalene and Methylnaphthalene Photooxidation

Chia-Li Chen cchen065@ucr.edu

Mary Kacarab Fishell, David R. Cocker III. Department of Chemical and Environmental Engineering, University of California, Riverside, Riverisde, CA 92521, United States

Polycyclic aromatic hydrocarbons (PAHs) play a significant role in semivolatile gas-phase emissions from anthropogenic sources, which include incomplete combustion emissions, wood-burning, and may be a major “missing” source of SOA. Secondary organic aerosols can be formed from oxidation of PAHs and their contributions to ambient fine particulate matter are not well understood. Large uncertainties in PAH derived SOA, fine particle aging properties, SOA formation mechanisms and their gas-particle transformation reaction pathway in the atmosphere that promote further investigation. The characteristics of SOA formation from oxidation of PAHs such as naphthalene and methylnaphthalene under the absence and presence of NOx conditions were conducted in the UCR CE-CERT chamber. SOA composition characteristics were identified by HR-ToF-AMS, and particle size distributions, particle density, SOA yield and particle volatility were investigated. This research provides a foundation for prediction of SOA formation from PAH precursors.

275. Radioactivity-induced charging and its influence on aggregation of radioactive particles in air

Costas Tsouris3 tsourisc@ornl.gov

Yong-ha Kim1, Sotira Yiacoumi1, Ida Lee2, Joanna McFarlane3(1) Department of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0373, United States (2) Department of Electrical Engineering and Computer Science, University of Tennessee, Knoxville, TN 37996, United States (3) Department of Energy and Transportation Science, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6181, United States

Accurate prediction of radioactivity transport in air is important in efforts to minimize potential damage to humans and ecosystems resulting from radiation exposure. Radioactivity can alter significantly the electrostatic characteristics of aerosol particles during the decay process. However, particle charging and its effects on mutual interactions have rarely been considered in transport modeling of radioactive particles. In this study, mechanisms of radioactivity-induced charging and effects on aggregation kinetics of radioactive particles are investigated. Scanning surface potential microscopy is employed to perform measurements of radioactivity-induced charging. A population balance model, considering particle interactions, is used to predict temporal changes in the size distribution of radioactive particles. Simulation results have indicated that radioactivity-induced charging hinders aggregation of radioactive particles via generation of strong repulsive electrostatic forces attributed to like charges. The effects of various parameters on the charging and aggregation of radioactive particles are investigated.

276. Effect of bursting bubbles on the fate of spilled oil

Paria Avij pavij1@lsu.edu

Victoria Dugas, Isaiah Woodson, Xin Shu, Thilanga Liyana-Arachchi, Franz Ehrenhauser, Francisco Hung, Kalliat Valsaraj. Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA 70803, United States

During the Deepwater Horizon Oil Spill, estimated 4.9 million barrels of crude oil were released into the Gulf of Mexico which followed multiple pathways. We investigate one of the potential transportation pathways of oil matter - aerosolization via bursting bubbles, as they are produced by oceanic whitecaps. We simulate the aerosolization process in a laboratory reactor in which bursting bubbles generate droplets, which are dried up to particulate matter by an air lift. Crude oil and dispersants are injected into the reactor. The resulting particulate matter is sampled and analyzed by gas chromatography. The injection of oil into the bubble column reactor results in the ejection of semi-volatile and non-volatile components of the crude oil. The addition of dispersant enhances the ejection of all compounds but is particular significant for non-volatile compounds. Our results indicate that the aerosolization of oil matter via bursting bubbles is indeed a potential transport vector.

277. Effects of gas-wall partitioning on the yields of alkyl nitrates measured for reactions of n-alkanes with OH radicals in a Teflon film chamber

Paul J. Ziemann paul.ziemann@ucr.edu

Geoffrey K. Yeh. Air Pollution Research Center and Department of Chemistry, University of California-Riverside, Riverside, CA 92521, United States

Organic nitrates are formed in polluted air from reactions of organic peroxy radicals with NO. They serve as sinks for NOx and thus affect tropospheric O3 formation, and the addition of nitrate groups to volatile organic compounds leads to less volatile products that are more likely to form secondary organic aerosol. The OH radical-initiated reactions of alkanes are a major source of organic nitrates, and yields have been measured for compounds with small carbon numbers. Quantifying yields of larger, less volatile products is more difficult, however, because of enhanced partitioning to reactor walls. Here I discuss studies conducted in a Teflon film environmental chamber to measure the yields of alkyl nitrates formed from reactions of C8–C14n-alkanes with OH radicals in the presence of NOx. The results demonstrate the challenges of conducting such studies with semi-volatile compounds and the importance of accounting for gas-wall partitioning of reaction products

278. Assembling two-directionally percolated particle networks using orthogonal electric and magnetic fields

Bhuvnesh Bharti bbharti@ncsu.edu

Orlin D. Velev. Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27606, United States

Electric and magnetic fields have been used individually to assemble colloidal particles into one, two or three dimensional structures. However, colloidal assemblies formed under the action of conjugated electric and magnetic field have not been characterized. In this study we report a single-step, facile and reversible method for the assembly of 2D biresposive structures. A mixture of magnetic and non-magnetic spherical latex particles is subjected to orthogonal electric and magnetic fields. A highly percolated and two-dimensionally interconnected structure is formed. The order of electric and magnetic field application determines the equilibrium morphology of assembled 2D structure In addition, modulating the number density of the biparticle dispersion controls the interconnectivity of the assembled structure. This experimental technique for the biparticle assembly offers a potential way for the fabrication of smart gels and biresponsive functional materials that can be useful in electronics and biomedical applications.

279. Carbon nanotube ponytails as rapid settling sorbent particles

Chongzheng Na chongzheng.na@gmail.com

Haitao Wang, Hanyu Ma. University of Notre Dame, Notre Dame, Indiana 46556, United States

Carbon nanotubes (CNTs) are promising candidate materials for developing next-generation water treatment technologies due to their high capacity and fast kinetics in contaminant sorption. The direct use of CNTs, however, faces a prohibitive challenge. Because CNTs do not settle well under gravity, processes employing them run the risk of releasing the potentially toxic nanomaterial in drinking water. To provide a viable solution to this challenge, we designed and fabricated carbon nanotube ponytails by bundling CNTs into colloidal particles.

280. Characterisation of particle morphology and dispersion stability via compressive rheology

Huai Nyin Yow h.n.yow@leeds.ac.uk

Simon R Biggs. Institute of Particle Science & Engineering, School of Process, Environmental and Materials Engineering, University of Leeds, Leeds, United Kingdom

Compressive rheology offers a simple alternative to characterise the stability of concentrated particle dispersions. This is achieved by de-stabilising the particle dispersion in an increasing centrifugal field and analysing the response of the particle network to the applied force. Our work investigates the stability of temperature-sensitive core-shell poly(ethylene glycol)-stabilised polystyrene particles as a function of temperature and electrolyte concentration. Stable particle dispersion forms an incompressible particle bed irrespective of centrifugal force, while an aggregated dispersion has stepwise bed compression that balances each applied force. The compressive response of the colloidal dispersion can also infer the particle morphology obtained under different conditions. With the growth in inkjet printing applications such as printed electronics, display panels, 3D-printing, etc, compressive rheology can help to characterize and understand ink formulations. This becomes critical as increasing ink solids content beyond the current 5vol% is a critical step towards better resolution and material deposition control.

281. Fluorescence Correlation Spectroscopy as a tool to directly study coalescence during nanoparticle preparation

David Schaeffel schaeffel@mpip-mainz.mpg.de

Roland Hinrich Staff, Hans Jürgen Butt, Katharina Landfester, Daniel Crespy, Kaloian Koynov. Max Planck Institute for Polymer Research, Mainz, Germany

One of the most common approaches for nanoparticles preparation is the use of emulsion droplets as templates. However, this approach has intrinsic drawbacks originating from the colloidal stability of the emulsions. Droplets coalescence can lead to a large size distribution of the obtained nanoparticles. Therefore, to optimize the nanoparticles preparation processes it is very important to monitor the nanodroplets coalescence quantitatively. Here, we show how dual color fluorescence cross-correlation spectroscopy, can be applied to monitor directly and unambiguously the coalescence during nanoparticles preparation from emulsions. To demonstrate the generality of our approach we studied three different preparation routines, namely the solvent evaporation process from emulsion droplets, miniemulsion polymerization and polycondensation to silica-nanocapsules. We found that while for the first two routines coalescence plays a minor role, a substantial aggregation of nanocapsules takes place during the polycondensation reaction to inorganic nanocapsules [1]. [1]Schaeffel et al., Nano Lett. 2012 , 12, 6012

282. Engineered-micelles and engineered-membranes: a novel concept for specific conjugation of detergent micelles and lipid bilayers

Guy Patchornik guyp@ariel.ac.il

Department of Biological Chemistry, Ariel University, Ariel, Israel

A highly specific and mild mechanism for conjugating, i.e. tethering, detergent micelles and lipid bilayers is presented. The mechanism does not require any precipitants, high ionic strength, temperature alterations or water-soluble polymers. Rather, it relies on complexes between hydrophobic chelators embedded within the micelle or membrane and appropriate metal cations in the aqueous phase, serving as mediators. This approach has been applied to a number of non-ionic detergents (e.g. C8E4, C12E5, OG, DDM) using diverse hydrophobic chelators and transition metals, thus demonstrating its potential generality. Parameters affecting process specificity and efficiency were studied with light microscopy, DLS, AFM and cryo-TEM. When applied to native phospholipid bilayers containing the membrane protein, bacteriorhodopsin, mm sized aggregates were generated in which the protein conformation remained unaltered for months during storage at 19C in the dark. Some applications of the tethering mechanism e.g. crystallization and purification of membrane proteins, will be presented.

283. Physical stability of nanoparticle dispersion

Jonathan Denis1 tisserand@formulaction.com

Guillermo Smart1, Christelle Tisserand2. (1) Applications, Formulaction Inc, Davie, Florida 33330, United States (2) Applications, Formulaction, L'Union, France

Nanoparticles applications in the industry are getting more and more important and concern many different field. Using new analytical techniques, it is now possible to control and tailor properties of suspensions and to get a better understanding of time behaviour. Following this idea, stability measurements, which were commonly done by simple visual observations, can now be performed automatically via an optical device. This instrument is based on Multiple Light Scattering and is associated to a vertical scanning of the sample. It enables to identify and quantify instability phenomena before they are visible to the operator (up to 200 times earlier). Physical parameters and kinetics can be computed in order to facilitate and improve sample comparison. Examples of CNT dispersibility measurements are presented using this technique and enable to fine tune the dispersion in terms of solvent, surfactant content etc.

284. How can magnetic resonance imaging (MRI) help understanding particle transport in the subsoil.

Eric Michel1,2 eric.michel@avignon.inra.fr

Pamela Faure4, Stephane Rodts4, Francois Lafolie1,2, Pierre Guillet3, Ange Polidori3, Sophie Neveu5. (1) UMR1114 EMMAH, INRA, Avignon, Cedex9 84914, France (2) UMR1114 EMMAH, UAPV, Avignon, Cedex9 84914, France (3) UMR5247 IBMM, UAPV, Avignon, France (4) UMR8205 Laboratoire Navier, IFSTTAR, Marne-la-Vallée, cedex2 77455, France (5) UMR7195 Laboratoire PECSA, Université Paris 6, Paris, France

Current models often fail to predict colloidal particle transport in the soil, indicating the need for a better understanding of the processes controlling particle attachment, detachment and transport in complex porous media. In order to tackle this issue, we synthesized maghemite nanoparticles (NP) and stabilized them by grafting onto their surface either sodium citrate (NP-Cit) or neutral hydrophilic poly(ethylene-glycol) polymer chains (NP-PEG). We then compared the transport properties of these particles in saturated repacked soil columns recording (1) the nanoparticle breakthrough curves (concentration as a function of time) and (2) their concentration in the soil as a function of depth and time using Magnetic Resonance Imaging (MRI). We will show how the MRI concentration profiles help discriminate between different models that can fit equally well the particle breakthrough curves. More generally, we will discuss how MRI is an unique tool to understand 'why' and 'where' particle retention occurs.

285. Effect of Carbon Nanotubes on the Transport and Retention of Bacteria in Saturated Porous Media

Haiyan Yang1 yanghaiyan@iee.pku.edu.cn

Meiping Tong1, Hyunjung Kim2. (1) College of Environmental Sciences and Engineering, Peking University, The Key Laboratory of Water and Sediment Sciences, Beijing 100871, China (2) Department of Mineral Resources and Energy Engineering, Chonbuk National University, Jeonju, Jeonbuk 561-756, Republic of Korea

This study investigated the influence of carbon nanotubes (CNTs) on the transport and deposition behaviors of bacteria (E.coli) in packed porous media in both NaCl and CaCl2 solutions with different aggregation states of CNTs. In 5 mM NaCl and 0.1 mM CaCl2 solutions where aggregation rates were low, both breakthrough curves (BTCs) and retained profiles (RPs) of bacteria with CNTs in solutions were equivalent as those without CNTs, indicating CNTs with low aggregation rates did not affect the transport and retention of E.coli in quartz sand. In contrast, in 25 mM NaCl and 0.4 mM CaCl2 solutions where CNTs were stable yet aggregation occured, bacteria BTCs with CNTs were lower than those without CNTs, demonstrating that CNTs with relatively high aggregation rates decreased transport of bacteria in quartz sand. The formation of cell-CNTs clusters was found to be the main contributor to the increased cell deposition with CNTs in suspensions.

286. Theoretical predictions of operating conditions to accelerate particle adsorption kinetics

Kunal Savaji kunalsavaji@gmail.com

Alexander Couzis. Chemical Engineering, City College of New York, New York, New York 10031, United States

Uniform monolayers of particles on a substrate find application in diverse fields like optical coatings, Layer by layer assembly etc. The outcome is strongly dependent on pH and ionic strength that affects both the magnitude of charge on the substrate and the NP surface. Motivated by improved packing of NP and better understanding of the adsorption process, we have characterized adsorption of nanoparticles on substrates using different particle stabilization mechanisms. To gain insight into the actual mechanism of the adsorption process, efforts are made to propose a model describing the kinetics of the electrostatically driven adsorption process. The model tries to incorporate the transport equations, energetics and the random sequential adsorption logic. Experimental results obtained with Silicon substrates and Polystyrene particles at different suspension conditions were compared with the results of the model. Based on the model, further predictions for accelerating the kinetics were made which cannot be made experimentally.

287. Dynamics of wet colloids under mechanical load studied by 3D confocal microscopy

Günter K. Auernhammer auhammer@mpip-mainz.mpg.de

Jennifer Wenzl, Marcel Roth, Rene Stangenberg. Physics at Interfaces, Max Planck Institute for Polymer Research, Mainz, Germany

Wet colloids are prevalent in many industrial applications, e.g. food processing, or pharmaceuticals. Detailed information of the microscopic behavior of wet colloids is still an open field. The challenge is the 3D visualization on the micro scale of the particle structure and liquid distribution, especially under mechanical deformation. We present a study on model wet colloids, which can be observed in 3D with confocal microscopy. For a high spatial resolution, the refractive index of all components has to be matched: Silica particles (diameter 7m) dispersed in a mixture of an aqueous salt solution and an immiscible organic solvent. Partial hydrophobization of the colloid surface allows us to change the contact angle of liquid-liquid interface, i.e. the interaction of the colloids with the liquid interface. We follow the reorganization of this model wet colloids under mechanical load on a single colloid level and discuss the effects due to capillary bridging.

288. Electrolyte dependent aggregation of colloidal particles near electrodes in a low frequency oscillatory electric field

Taylor J Woeh tjwoehl@ucdavis.edu

Cari S Dutcher, Kelley Heatley, William D Ristenpart. University of California, Davis, Davis, California 95618, United States

Colloidal particles adjacent to charged electrodes have been observed to exhibit drastically different electrohydrodynamic (EHD) aggregation behavior depending on the suspending electrolyte. Previous models have only been able to predict whether the electrolyte will cause particle aggregation or separation, but have not provided a concrete physical mechanism for the difference in particle behavior. Here we show that the electrolyte dependent particle aggregation is explicable in terms of the EHD flow magnitude predicted by a scaling analysis. The particle aggregation rate, AC electric field, and zeta potential of particles were experimentally measured for a number of electrolytes. We employ a previously formulated electroosmotic slip scaling analysis and compute the EHD flow magnitude for each electrolyte suspension, and find good agreement with the experimental aggregation rates. Counter intuitively, the aggregation rate and predicted EHD flow magnitude decrease with increasing particle zeta potential.

289. Using QCM-D to characterize the size of engineered nanoparticles

Adam L.J. Olsson adam.olsson@mcgill.ca

Danqing He, Ivan Quevedo, Mohan Basnet, Nathalie Tufenkji. Department of Chemical Engineering, McGill University, Montreal, QC Quebec H3A 2B2, Canada

A quartz crystal microbalance with dissipation (QCM-D) was used to determine size of engineered nanoparticles by “weighing” the particles as per the piezoelectric effect of a quartz crystal sensor. The method, reported in literature for viruses and liposomes, is here applied for engineered polymer-coated nanoparticles of varying complexity (i.e., polymer-coated metal particles and polydisperse suspensions of polystyrene latex particles). Sizes obtained from QCM-D, for particles ranging from a few nm up to a hundred nm, are shown to be in closer agreement with the nominal particle sizes determined by TEM rather than with the nanoparticle aggregate sizes obtained by light scattering techniques (such as DLS and NTA). The use of these latter techniques has been criticized because the scattering intensity varies strongly with the particle diameter, thereby biasing the interpretation of particle size toward larger particle sizes. Likewise, sample preparation for TEM may introduce multiple artifacts in particle sizing measurements.

290. The diffusion of nanoparticles and molecules at the water-oil interface

Hans-Juergen Butt1 butt@mpip-mainz.mpg.de

Dapeng Wang1, Stoyan Yordanov1, Christopher Y. Li2, Klaus Muellen1, Harsha Mohan Paroor1, Ashis Mukhopadhyay3. (1) Max Planck Institute for Polymer Research, Mainz, Germany (2) Department of Materials Sci. & Eng., Drexel University, Philadelphia, Pennsylvania 19104, United States (3) Department of Physics & Astronomy, Wayne State University, Detroit, Michigan 48201, United States

To better understand the properties of the water-alkane interface, the interfacial diffusion of isolated molecular tracers and nanoparticles was measured using fluorescence correlation spectros-copy (FCS). Hydrophilic and hydrophobic quantum dots of 5, 8, and 11 nm hydro-dyna-mic radius diffused 1.5-2 times more slowly than in the bulk (Small 2011 , 7, 3502); the effect was most evident at the water-decane interface, where the viscosities of both liquids were similar. For a surface active dendrimer the two-dimensional interfacial diffusion coefficient agreed with what one would expect for the viscosities of the two phases. In contrast, rhodamine 6G faster than in the bulk (Phys. Rev. E 2013 , 87, 012403). The results may be interpreted assuming that a depletion layer exists between the alkane and water phase.

291. Hexatic-to-disorder transition in colloidal crystals near electrodes

William D Ristenpart wdristenpart@ucdavis.edu

Cari S Dutcher, Taylor J Woehl, Nicholas H Talken. Department of Chemical Engineering and Materials Science, University of California, Davis, Davis, California 95616, United States

Colloids are known to form two-dimensional, hexagonal closed packed (HCP) crystals near electrodes in response to electrohydrodynamic (EHD) flow. Previous work by several groups has established that the EHD flow magnitude increases as the applied AC frequency decreases. Here we report that the HCP crystals instead undergo an order-to-disorder transition at sufficiently low frequencies, despite the increase in the attractive EHD driving force. For an HCP colloidal crystal formed at ~500 Hz, a decrease in frequency below approximately 250 Hz causes a crystalline structure transition to randomly close packed (RCP) with an orientational order parameter significantly less than one. Independent measurements of the EHD aggregation rate confirm that the EHD driving force is indeed higher at the lower frequencies. We present evidence that the order-disorder transition is instead caused by an increased particle diffusivity associated with a corresponding increase in the particle height over the electrode induced at lower frequencies.

292. Hydrodynamic Behavior of Carbon Nanotubes and Characterization of Length Distributions

Carlos A. Silvera Batista cas3@nist.gov

Constantine Y. Khripin, Ming Zheng, Xiaomin Tu, Jeffrey A. Fagan. Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States

Single-walled carbon nanotubes (SWCNTs) are 1D, cylindrical, structures of carbon with long persistence lengths and consistent diameters. I will discuss the use of doubly sorted SWCNTs (by buoyancy and length) to explore experimentally the effectiveness of theoretical approximations for the hydrodynamic drag of freely rotating rods. The objective of this work is to establish the use of Analytical Ultracentrifugation (AUC) to measure the length distribution of rodlike colloidal particles. This is particularly necessary for applications of nanotube dispersions, as the transport, optical, as well as the toxicity of SWCNTs have been demonstrated to depend on the length. Contrary to AFM, AUC can measure the whole population of particles in liquid phase. I will present AUC measurements and analysis of SWCNT samples with narrow distributions in length, diameter and buoyancy and compare them to independent AFM measurements. Using this data, the validity of hydrodynamic theory for this application is verified.

293. Solvent relaxation NMR studies of polymer competition in aqueous systems

Catherine L Cooper1 Catherine.Cooper@bristol.ac.uk

Terence Cosgrove1, Jeroen S van Duijneveldt1, Martin Murray2, Stuart W. Prescott1. (1) Department of Chemistry, The University of Bristol, Bristol, Avon BS8 1TS, United Kingdom (2) AkzoNobel, Slough, Berkshire SL2 5DS, United Kingdom

Solvent relaxation NMR can be used to investigate polymer adsorption to nanoparticles.Here we outline recent studies where there is competition for polymer adsorption by different surfaces; this is of particular interest in industrial formulations, which usually contain a wide range of components. Figure 1 shows the situation in which there is competition between particles with different surface chemistries. The relaxation rate was predicted for each adsorption scenario, and we found that PVP is preferentially adsorbed to silica particles.

294. Self-assemblies of highly methyl-branchedhydrocarbon surfactants in supercritical carbon dioxide

Masanobu Sagisaka sagisaka@cc.hirosaki-u.ac.jp

Kotaro Kudo, Junichi Oasa, Shota Nagoya, Shioki Narita, Misaki Niwase, Tsuyoshi Narumi, Atsushi Yoshizawa. Graduate School of Science and Technology, Hirosaki University, Hirosaki, Aomori 036 8561, Japan

To develop an efficient and fluorine-free solubilizer for a water/supercritical CO2 microemulsion (W/CO2 µE), in this study, highly methyl-branched alkyls, especially isostearyl group were focused on as CO2-philic tails, and the custom-made hydrocarbon surfactants were synthesized. The surface tension (?) of an aqueous surfactant solution was measured at ambient pressure as a function of surfactant concentration, and it was found to be ~25 mN/m at concentrations above their cmcs. A low ? value can generally be reached only by a fluorocarbon surfactant, which implies that these surfactants have an excellent solubilizing power for the W/CO2 µE, similar to some fluorocarbon surfactants reported previously. Some of the surfactant/W/CO2 mixtures revealed the formation of transparent single phases without separated water, identified as W/CO2 µE. The µE was well-stabilized at pressures >210 bar and temperatures > 55 C.

295. Experimental study of immiscible fluid replacement in a heterogeneous microfluidic pore-network

Peng He phe@lanl.gov

Sowmitri Tarimala, Amr I. Abdel-Fattah, James W. Carey, Hakim Boukhalfa. Division of Earth and Environmental Sciences, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States

Displacement of fluids in porous media is an important process in many environmental and industrial applications including pollution and remediation of non-aqueous phase liquids, geologic CO2 sequestration in saline aquifers, and enhanced oil recovery. Characterization of fluid displacement processes at pore scale provides crucial information to better understand macroscopic processes at micro-scale and to improve multi-scale computational models. We present here microfluidic experiments of immiscible fluid replacement at ambient conditions using a heterogeneous pore-network that represents the realistic subsurface flow in complex geologic medium. Quantitative information of flow pattern, interfacial length, and saturation levels are extracted from direct visualization. The data demonstrate remarkable impact of porosity heterogeneity on the local capillary trapping and bypass of fluids, which is largely missed by previous studies performed using homogeneous micromodels. Preliminary results of fluid replacement in pore-network under high-pressure/high-temperature conditions will also be presented. (LA-UR-13-20819)

296. Topical ophthalmic drug delivery

Clayton J. Radke1,2 radke@berkeley.edu

Cheng-Chun Peng1. (1) Department of Chemical and Biomolecular Engineering, University of California, Berkeley, Berkeley, CA 94720, United States (2) Vision Science Group, University of California, Berkeley, Berkeley, CA 94720, United States

Despite considerable inefficiency, topical ophthalmic drug delivery remains the main application modality to the human eye. We present a new description of tear dynamics that quantifies drug bioavailability by topical administration. The tear supply/drainage system is divided into 5 compartments: upper and lower menisci, upper and lower conjunctival sacs, and tear film. Transient description is provided for each compartment for tear, salinity, and drug. Compartments are coupled to each other and to drug pharmacokinetics (PK) through kinetic routes. The model can be integrated with available PK models to improve drug-uptake prediction in both the anterior and vitreous chambers. Further, the model is suitable for quantifying ocular drug delivery by other vehicles including contact lens, and emulsion and nanoparticle suspensions. Emphasis is made on the importance of quantifying drug equilibrium and transport properties. We provide a new tool to optimize multi-drug, multi-dose administration strategies for both normal and dry-eye subjects.

297. Doubly crosslinked microgel / polyelectrolyte complexes: Three simple methods to tune and improve gel mechanical properties for regenerative medicine applications

Brian R Saunders brian.saunders@manchester.ac.uk

School of Materials, University of Manchester, Manchester, England M13 9PL, United Kingdom

Doubly crosslinked microgels (DX MGs) are hydrogels composed of covalently-interlinked microgels. They are injectable and have potential application in soft tissue repair. Here, we investigate the effect of added polyelectrolyte and NaCl on the mechanical properties of the gels[1]. Addition of polycations improved ductility and decreased the storage modulus (G') of the DX MG / polyelectrolyte complex (DX MG / PECs) gels. The best DX MG / PEC gel had a yield strain of 109%, which is the highest reported to date for any DX MG. Our DX MG / PEC gels maintained high G' values as well as good ductility when swollen at pH = 7.5. We investigated the effect of addition of NaCl during DX MG and DX MG / PEC preparation. This caused remarkable increases in both G' and ductility. Addition of linear polyacrylic acid also increased G' values. [1] Soft Matter, 8, 10932, 2012

298. Engineered peptides for breast cancer targeted delivery of doxorubicin

Kamaljit Kaur kkaur@ualberta.ca

Rania Soudy, Mostafa Shahin, Afsaneh Lavasanifar. Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta T6G2E1, Canada

Cancer treatment using chemotherapy is constantly challenged by poor selectivity and limited access of drugs to the cancer cells. Targeted drug delivery methods have been explored to improve drug efficacy, selectivity, and lower side effects by directing the drug to a specific cell type. In recent years, a number of peptides have been identified for targeting specific tumor cells. These cancer targeting peptides bind cancer cells with high specificity, and show promising results in delivering drugs and diagnostic elements into tumors. Using peptide array-whole cell binding assay, we have identified several cancer targeting peptides which selectively bind breast cancer cells. We have applied a novel strategy to develop proteolytically stable peptide analogues that retain targeting ability of the peptides in vivo. Further peptide-doxorubicin conjugates as well as peptide-liposomal doxorubicin formulations have been used to deliver active drug in a cell-specific fashion, and overcome multidrug resistance.

299. Optimizing nanoparticles for brain tumor immunotherapy

Jacob M Berlin1 jberlin@coh.org

Yiming Weng1, Huaqing Wang2, Anna Carvalho da Fonseca2, Ethan White1, Hui Ren2, Anil K Suresh1, Leying Zhang2, Ian Zhang2, Xuebo Chen2, Behnam Badie2. (1) Department of Molecular Medicine, Beckman Research Institute at City of Hope, Duarte, CA 91010, United States (2) Department of Surgery, Beckman Research Institute at City of Hope, Duarte, California 91010, United States

Even when treated with aggressive current therapies, most patients with primary or metastatic malignant brain tumors survive less than two years. We recently demonstrated that even a single low-dose injection of an immunotherapy agent (CpG) conjugated to carbon nanotubes eradicated brain tumors in animal models and protected surviving animals from tumor rechallenge. Here we describe optimizing this novel immunotherapy strategy for treatment of human brain tumors.

300. Cavitand-mediated endocytosis into live cells

Yoo-Jin Ghang yghan001@ucr.edu

Richard J Hooley. Department of Chemistry, University of California, Riverside, Riverside, CA 92521, United States

Receptor-mediated endocytosis (RME) is a process of the entry of a small molecule into a cell by its binding to a specific receptor on the cellular membrane. In RME, molecular recognition and selectivity at membrane interfaces are crucial. Deep cavitands can be considered artificial membrane-bound receptors due to their ability to selectively recognize small molecules. The presence of water-soluble cavitand increased the incorporation rate of guest transport into the cells in a short incubation time with no observed cytotoxicity.

301. Molecular simulation study of wetting and drying behavior

Jeffrey R Errington jerring@buffalo.edu

Chemical and Biological Engineering, University at Buffalo, Buffalo, NY 14260-4200, United States

We first describe our recent efforts aimed at development of Monte Carlo simulation methods for determining the wetting properties of fluids at solid surfaces. Our strategy involves calculation of the surface excess free energy (also referred to as the interface potential) as a function of the surface density of a fluid in contact with the substrate at a specified temperature and chemical potential. The shape of this curve provides qualitative insight regarding the system's wetting behavior (e.g. partial wetting, complete wetting) and quantitative analysis provides macroscopic interfacial properties, such as the spreading coefficient and interfacial tension. We describe how components of the interface potential are obtained via grand canonical transition matrix Monte Carlo simulation and various expanded ensemble Monte Carlo simulation strategies. We then show examples of the application of this general strategy to geometric and chemically heterogeneous surfaces, aqueous systems, and room temperature ionic liquids.

302. The interfacial free energy of a hard-sphere fluid at a curved surface

Brian B Laird1 blaird@ku.edu

Ruslan L Davidchack2. (1) Department of Chemistry, University of Kansas, Lawrence, KS 66045, United States (2) Department of Mathematics, University of Leicester, Leicester, United Kingdom

The interfacial free energy of a fluid, ?, at a curved surface is a central component in determining the solvation free energy of colloidal particles. In this work, we calculate using molecular-dynamics simulation and Gibbs-Cahn integration, the values of ? for a hard-sphere fluid at spherical and cylindrical colloidal hard surfaces for a large range of fluid densities and surface curvatures. These results are used to test the validity in these systems of Hadwiger's theorem, which states that the curvature dependence of ? is determined completely by (and linearly dependent upon) the mean and Gaussian curvatures of the surface. We find that Hadwiger form holds well at low and intermediate fluid packing fractions, but that marked devations are seen above packing fractions of about 0.42.

303. Interface potential and film thick dependent surface tension of adsorbed liquid films.

Luis G. MacDowell1 lgmac@quim.ucm.es

Jorge Benet1, Nebil A. Katcho2, Eva M. Fernández3, Enrique Chacón3, Pedro Tarazona4. (1) Departamento de Química Física, Universidad Complutense de Madrid, Madrid, Madrid 28040, Spain (2) Unite d ' Electronique Imprimee, Le Laboratoire d’Innovation pour les Technologies des Energies Nouvelles et les nanomatériaux (LITEN), Grenoble, France (3) Instituo de Ciencia de los Materiales, Consejo Superior de Investigaciones Científicas, Madrid, Madrid 28048, Spain (4) Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, Madrid, Madrid 28049, Spain

We study the capillary wave fluctuations of an adsorbed liquid film on a solid exhibiting long range interactions. We show that independent measurements of the interface potential (red lines) are fully consistent with expectations from the clasical capillary wave spectrum (green symbols). However, the film thick dependent surface tension that results (blue symbols) may be only explained using an improved theory of capillary waves that accounts for broadening of the density profile beyond mere interfacial displacements (yellow line).

304. Solvent cavitation under solvophobic confinement

Henry S. Ashbaugh hanka@tulane.edu

Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, LA 70118, United States

The stability of liquids under solvophobic confinement can tip towards the vapor phase, nucleating an evaporation transition that induces attractive surface forces. The macroscopic theory of cavitation under confinement connects the size of the confining surfaces, interfacial tensions, and pressure with the critical evaporation separation and interfacial forces. While simulations have confirmed the broad trends, a quantitative comparison based on independent measurements of the interfacial tension and coexistence properties has, to the best of our knowledge, not yet been performed. Here we simulate cavitation of a confined two-dimensional Lennard-Jones fluid over a range of plate sizes and pressures. Our simulations confirm the predicted forces and critical separations once the length dependence of the solvation free energy of the confining plates is taken into account. The length dependence of the solid-liquid tension results from molecular scale correlations that asymptotically decay to the macroscopic limit for plates longer than 150 solvent diameters.

305. Drops and bubbles on curved surfaces

Majid Soleimani1 majid.soleimani@mail.mcgill.ca

Reghan J Hill1, Theo G.M. van de Ven2. (1) Department of Chemical Engineering, McGill University, Montreal, Quebec H3A OC5, Canada (2) Department of Chemistry, McGill University, Montreal, Quebec H3A 2K6, Canada

A curved support can affect the shape, stability, and contact angle of sessile and pendant drops. We developed an approximate analytical solution for drops on a curved surface in the absence of gravity. This furnishes the drop shape, pressure, and interfacial energy when a spherical drop on a planar support is perturbed by substrate curvature while maintaining a fixed contact angle and volume. The analytical theory is validated by comparison with numerical solutions of the Laplace equation from the Surface Evolver software. We quantify how contact angle and surface curvature affect the drop shape, internal pressure, and surface energy. The total energy furnishes a driving force for lateral migration that is driven by a lateral gradient of substrate surface curvature. For 1 µm diameter drops on a surface with a curvature gradient of 1011 m-2, forces on the order of 10-8 N can be achieved.

306. The Impact of Geometric Anisotropy on Colloids under Electric Fields

Fuduo Ma fma@mines.edu

Ning Wu ningwu@mines.edu

Sijia Wang, David T. Wu. Department of Chemical and Biological, Colorado School of Mines, Golden, Colorado 80401, United States

Colloids possessing anisotropic interactions assemble in more diversified structures than isotropic particles. Here, we investigate the impact of geometric anisotropy on the assembly of colloidal dimers on conducting substrates under electric fields. By systematically tuning the size ratio between two lobes, we found that interactions between dimers are strongly dependent on their relative orientations. For example, attractive interactions exist between lying and standing dimers on the substrate. When all dimers stand on the substrate, they experience attraction if neighboring dimers have alternating orientations. Otherwise, they feel repulsive forces. Such orientation-dependent interactions generate various new structures, such as chiral clusters and dimer crystals with alternating orientations. We will discuss the physical origin of those orientation-dependent interactions and the impacts of experimental conditions such as the ionic concentrations and surface charges. Our numerical model based on electrostatics agrees well with experimental observations and provide further insights on electric-field assembly of anisotropic particles.

307. Effect of Network Geometry on Electron Transport in a TiO2 photoanode of a Dye-sensitized Solar Cell (DSSC)

Ilona Kretzschmar kretzschmar@ccny.cuny.edu

Department of Chemical Engineering, The City College of New York, NY 10031

DSSCs have garnered considerable attention because of their low production costs. They are based on a layer of TiO2 nanoparticles (NP), which maximizes the optical path of incident light and provides efficient contact with the electrolytic solution. While the disordered NP network has a high surface area maximizing photogenerated electron density, it also has a large number of surface states limiting electron transport and efficiencies. An interconnected photoanode architecture in the form of an inverse opal (IO) structure may improve electron transport. TiO2 IOs fabricated via self-assembly of colloidal particles followed by TiO2 precursor infiltration and calcination at 450°C are electrochemically evaluated and incorporated into a DSSC configuration for tests in indoor light. In IO electrodes, the number of surface traps scales with surface area per unit volume and better conductivity and less recombination are observed than for the standard NP electrode leading to higher power output in indoor illumination.

308. Location specific self-assembly of vertical nanowire arrays via lithographic micro-features

David J Kirby djk291@psu.edu

Benjamin D Smith, Christine Keating. Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, United States

Developing high-density vertical arrays of long nanowires (> several µm) is challenging. Here, self-assembly was directed by gravitational sedimentation of particles into lithographic microwells. Nanowires (4-10 µm long and ca. 300 nm diameter) were assembled at selected locations with up to 100% vertically orientated. Microwell dimensions forced particles that normally orientated horizontally to adopt vertical ones. Nanowire position and orientation were retained in microwells as samples were dried and anchored to a surface.

309. Silica nanoparticles grafted with a weak polybasic brush: Ionic strength and pH-dependent adsorption to the silica/aqueous interface

John K. Riley1 jkriley@andrew.cmu.edu

Robert D. Tilton1,2. (1) Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, United States (2) Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, United States

The adsorption of spherical silica nanoparticles grafted with a brush layer of poly(n,n-dimethylaminoethyl methacrylate) (Si-g-PDMAEMA) to flat silica surfaces from aqueous salt solutions is studied using ellipsometry. Si-g-PDMAEMA adsorption is driven by electrostatic attraction to the surface but the saturation coverage is primarily governed by interparticle electrostatic repulsions, and these competing effects are investigated over a range of pH and ionic strengths. Both double layer screening and pH-induced deprotonation of DMAEMA monomers can lead to increased particle packing on the surface. Brush swelling and electrophoretic mobility of the particles are measured in suspension. Streaming potential measurements obtained from a rotating disk apparatus are used to gain insight into the charge compensating ability of the adsorbed particles. The adsorption of Si-g-PDMAEMA will be compared to linear PDMAEMA homopolymer with a molecular weight comparable to the individual Si-g-PDMAEMA arms. Force measurements between surfaces coated with Si-g-PDMAEMA particles will also be discussed.

310. Tuning the morphology of surfactant surface aggregates

Bhuvnesh Bharti bbharti@ncsu.edu

Gerhard H. Findenegg. Stranski Laboratorium, Institut für Chemie, Technische Universität, Berlin, Berlin 10623, Germany

Self assembly and adsorption of nonionic surfactants in/on nanomaterials plays an important role in various industrial applications. Here we present a method to control the morphology of surfactant aggregates in the presence of silica nanomaterials. Addition of a surface modifier (lysine) to a silica nanoparticle dispersion with adsorbed nonionic surfactants can lead to complete desorption and formation of cylindrical micelles in the aqueous phase (Bharti et al., Soft Matter, 2012 ). Surface modification also changes the adsorption and aggregate structure of nonionic surfactants in the cylindrical mesopores of SBA-15 ordered mesoporous silica. Using neutron scattering we have found that by modulating the surfactant aggregates to pore-wall interaction threadlike micelles, although entropically unfavorable, can be stabilized in the 8 nm channels of SBA-15 silica substrate (Bharti et al., JACS, 2012 ). We propose that this method of fine-tuning interactions with surfaces may also be applicable to other types of amphiphiles and polymers.

311. From multi-ring and radial spoke to spider net and foam: Pattern formation from drying colloidal drop

Xin Yang1 xinyang3721@gmail.com

Christopher Li2, Ying Sun1. (1) Mechanical Engineering and Mechanics, Drexel University, Philadelphia, Pennsylvania 19104, United States (2) Material Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States

Deposition morphologies of inkjet-printed colloidal drops containing nanoparticles of different concentrations are examined under different drying conditions. A variety of deposition patterns from multi-rings and radial spoke to spider net and foam structures are observed. For a drop with high particle loading, the deposition pattern within a single drop transitions from circumferential stripes near the drop edge to spider-net-like structure and finally to foams and islands in the drop center. This morphology transition is a result of increasing contact line velocity while keeping a constant deposition rate per unit length of the contact line during drop evaporation. Fingering instability of the shrinking contact line attributes to the spider-net-like deposition and saw-toothed structures, whose wavelengths quantitatively follow the linear stability theory. For a drop with low particle loading, the deposition morphology transitions from radial spoke near the edge to islands in the center, where the spoke spacing also follows fingering instability

312. Unilever Award Lecture- Chemical Transformations on the Nanoscale

Prashant K. Jain jain@illinois.edu

Department of Chemistry, University of Illinois Urbana Champaign

Intermediates or transition states in chemical reactions involving small molecules are well understood. However, we are missing a similar level of insight into the dynamics of transformations in extended solids. This is despite the utility of this knowledge in catalysis, solid-state devices, heterostructure fabrication, and materials’ degradation in reactive environments. My lab is taking a unique approach towards developing such understanding of solid-state transformations. Whereas, kinetic studies on bulk materials provide a picture averaged over multiple domains or crystallites, we monitor chemical transformations on the level of single nanocrystals. This is accomplished using in-situ single-particle optical spectroscopy. The objective is to glean from single-particle trajectories previously unknown information about dynamical pathways or nucleation in the solid-state transformation. In particular, we are using single-particle studies to elucidate the dynamics of a) impurity doping in chalcogenide nanocrystals, b) self-assembled monolayer formation on single gold nanoparticles, and c) galvanic exchange of single silver nanoparticles.

312. Unilever Award Lecture- Chemical Transformations on the Nanoscale

Prashant K. Jain jain@illinois.edu

Department of Chemistry, University of Illinois Urbana Champaign

Intermediates or transition states in chemical reactions involving small molecules are well understood. However, we are missing a similar level of insight into the dynamics of transformations in extended solids. This is despite the utility of this knowledge in catalysis, solid-state devices, heterostructure fabrication, and materials’ degradation in reactive environments. My lab is taking a unique approach towards developing such understanding of solid-state transformations. Whereas, kinetic studies on bulk materials provide a picture averaged over multiple domains or crystallites, we monitor chemical transformations on the level of single nanocrystals. This is accomplished using in-situ single-particle optical spectroscopy. The objective is to glean from single-particle trajectories previously unknown information about dynamical pathways or nucleation in the solid-state transformation. In particular, we are using single-particle studies to elucidate the dynamics of a) impurity doping in chalcogenide nanocrystals, b) self-assembled monolayer formation on single gold nanoparticles, and c) galvanic exchange of single silver nanoparticles.

313. Victor K. LaMer Award Lecture- Self-assembly of Nanoparticles using External Stimuli

Rafal Klajn rafal.klajn@weizmann.ac.il

Department of Organic Chemistry, Weizmann Institute of Science, Israel

Self-assembly has emerged as a method of choice for organizing nanoparticles into higher-order structures, and ultimately macroscopic materials. Among the different ways to induce self-assembly, those based on using external stimuli as a trigger are the most attractive as the external signals can be delivered to a closed system, and can be “turned off” at will. This talk will describe methodologies developed to assemble nanoparticles using light and magnetic fields as the external stimuli. To achieve these goals, we decorated the surfaces of metallic nanoparticles with monolayers of photoresponsive molecules, and employed differently shaped superparamagnetic nanoparticles, respectively. In addition, by chemically functionalizing the surfaces of magnetic nanocrystals with light-responsive ligands, we synthesized “dualresponsive” nanoparticles, whose behavior can be tailored with magnetic field and light in an orthogonal fashion. This design has enabled a unique goal of manipulatingnon magnetic (diamagnetic) objects with the help of magnets.

314. Biological and chemical insights from physical measurements of objects in fluid

William H. Grover wgrover@engr.ucr.edu

Department of Bioengineering, University of California, Riverside, Riverside, CA 92521, United States

The fundamental physical properties of an object can provide novel biological or chemical information about the object. In this talk I will show how we use a microfluidic mass sensor to precisely measure the physical properties of single living cells and particles in fluid. The mass sensor we use, the Suspended Microchannel Resonator (SMR), consists of a micron-sized vibrating silicon cantilever containing an embedded microfluidic channel. When an object passes through the cantilever, the object's buoyant mass is measured as a change in the resonance frequency of the cantilever. By using the SMR to weigh a cell twice in fluids of different densities, the cell's mass, volume, and density can be determined. We have found that for many samples, density is much more meaningful than mass or volume, and density measurements can provide detailed information about the biology of a cell or the chemistry of a particle.

315. Influence of relative humidity on spreading, pattern formation and adhesion of a drying drop of whole blood

David Brutin david.brutin@polytech.univ-mrs.fr

Wassim Bouzeid. Mechanical Engineering, Aix-Marseille University, Marseille, France

Our experimental work aims to investigate the effect of relative humidity on the spreading behavior and on the pattern formation of a dried drop of whole blood at the end of the evaporation process. Drops of blood of same volume are gently deposited on ultraclean microscope glass substrates. A top-view camera allows for the monitoring of the drying regime (deposition, gelation and fracturation). We show that humidity influences the contact angle, and the final wetting diameter and consequently, the final deposition pattern at the end of the evaporation process. A good agreement has been observed between our results for whole blood and the experimental work of Chhasatia et al. 2010) performed an aqueous drop of 1.1 microns colloids. Our experimental measurements are in a good agreement with the purely diffusive model where the wetting diameter and the contact angle are function of humidity.

316. Brownian Coagulation Kinetics in Concentrated Dispersions

Aniruddha V Kelkar kelkara@purdue.edu

Elias I Franses, David S Corti. School of Chemical Engineering, Purdue University, West Lafayette, Indiana 47907, United States

Colloidal dispersion stability is important in several applications including inkjet printing, paint formulation, and flow assurance in oil and gas production. One destabilization mechanism of colloidal dispersions is Brownian coagulation. Smoluchowski (1916) first modeled the steady-state Brownian coagulation of initially mono-disperse hard spheres starting from a uniform concentration profile. However, this model is only accurate for particle volume fractions, F, less than 0.0005 (Kelkar et al. (2013)). We have developed a new rigorous model that accounts for transient, entropic packing and non-ideal particle diffusion effects in coagulation in concentrated colloidal dispersions. The model predicts significantly higher, about two orders of magnitude, rates of coagulation compared to those of Smoluchowski. The model predictions are in good agreement with Brownian Dynamics Simulation results up to F=0.35. The trends for enhancement in coagulation rates with concentration agree with previous Lattice-Boltzmann studies of Heine and Pratsinis (2007).

317. Measurement of rotation and translation of polydispere spherical particles in cohesive colloidal systems

Günter K. Auernhammer1 auhammer@mpip-mainz.mpg.de

Jennifer Wenzl1, Ryohei Seto2, Marcel Roth1, Hans-Jürgen Butt1(1) Physics of Interfaces, Max Planck Institute for Polymer Research, Mainz, Germany (2) Benjamin Levich Institute for Physico-Chemical Hydrodynamics, New York, New York NY 10031, United States

Single particle dynamics in colloidal systems include (in the simplest case) translations and rotations of the colloids. To explore these dynamical processes, we use a combination of 3D imaging and mechanical testing. We analyze structural changes using confocal microscopy while applying a mechanical load simultaneously. Fluorescently labeled polydisperse silica particles were hydrophobized with long alkyl chains and dispersed in an index-matching liquid. The particles show a weak attraction. Photobleaching the central plane of individual particles generates an optical anisotropy without changing particle interaction. In a series of 3D images, we follow trajectories and rotation of single particles. We focus on particle translation and rotation in dependency of the local volume fraction. During compression, restructuring happens predominantly in regions of low packing density. We show that rotation plays an important role and is hence a key parameter for explaining dynamical processes in granular systems.

318. Microfluidic Space-Domain Time-resolved Emission Spectroscopy of Terbium (III) and Europium(III) Chelates with Pyridine-2,6-dicarboxylate

Vicente Nunez1 vnune004@ucr.edu

Srigoku xl Upadhyayula1,2, Brent Millare1,4, Ali Hadian1, Sanghoon Shin1, Prashanthi Vandrangi1, Jillian Larsen1, Sharad Gupta1, Hong Xu1, Adam Lin1, Georgi Georgiev5, Valentine I Vullev1,2,3. (1) Department of Bioengineering, University of California Riverside, Riverside, CA 92507, United States (2) Department of Biochemistry, University of California, Riverside, Riverside, CA 92507, United States (3) Department of Chemistry, University of California, Riverside, Riverside, CA 92507, United States (4) Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, United States (5) Department of Natural Sciences, Assumption College, Worcester, MA 01609, United States

This research describes the utilization of laminar microflows for time-resolved emission measurements with steady-state excitation and detection. Pyridine-2,6-dicarboxylate (dipicolinic acid or DPA) is a natural component of bacterial endospores and it is important for making endospores some of the most resilient life forms known on Earth. Complexationof lanthanides with DPA results in luminescent chelates that serve as indicators of sterilization. By imaging microfluidic flows carrying chelates of DPA-Terbium (III) and DPA-Europium (III), photoexcited in short regions of microchannels, we extracted the excited-state lifetimes of such complexes from the spatial distribution of the changes in the emission intensity. The lifetime values obtained using this microfluidic space-domain approach matched the lifetimes from established time-domain measurements. The thus validated space-domain microfluidic approach reveals a means for miniaturization of time-resolved emission spectroscopy with biosensing applications.

319. Developing quantum dot solids for thin-film photovoltaics

Matt Law lawm@uci.edu

Department of Chemistry, University of California, Irvine, United States

Colloidal semiconductor quantum dots (QDs) are attractive building blocks for solar photovoltaics (PV). In this talk, I will provide an overview our ongoing efforts to design lead salt QD thin film absorbers for next-generation PV. I will first discuss several methods used to make conductive QD films by solution deposition and ligand exchange. Studies of carrier mobility as a function of basic film parameters such as inter-QD spacing, QD size, and QD size distribution have led to a better understanding of charge transport within highly disordered QD films. Engineering the inter-QD matrix to produce QD/inorganic or QD/organic nanocomposites is introduced as a promising way to optimize coupling, remove surface states, and achieve long-term environmental stability for high-performance, robust QD films. The relative roles of superlattice order, energy disorder, and surface states in controlling the minority carrier diffusion length will be summarized.

320. Correlating Spectroscopy with Photocatalytic Activity of Au@TiO2 Core-Shell Nanostructures

Robert J Dillon robert.dillon@email.ucr.edu

Ji-Bong Joo, Francisco Zaera, Yadong Yin, Christopher J Bardeen. Department of Chemistry, University of California Riverside, Riverside, CA 92521, United States

This work investigates the spectroscopic and photocatalytic properties of a series of colloidal Au@TiO2 yolk-shell nanostructures, where the crystallinity of the TiO2 shells was varied by changing the etching and calcination conditions. The goal of the work is to identify spectroscopic observables that correlate with the measured hotocatalytic activity of the particles. By measuring the H2 production under ultraviolet illumination, a strong correlation between TiO2 shell crystallinity and the H2 production rate was found. Time-resolved photoluminescence experiments on these samples showed that the lifetime of the photoluminescence increases with sample crystallinity, providing a good correlation with photocatalytic activity. But this correlation is only found when the excitation wavelength is less than or equal to 300 nm. Our results imply that photoexcitation with high energy photons can generate both reactive surface sites and photoluminescent surface sites in parallel, which then undergo similar electron-hole recombination processes.

321. Flexible TiO2 three-dimensional nanowire array for visible light photoelectrochemical water splitting

Fan Zuo fzuo001@ucr.edu

Department of Chemistry, University of California Riverside, Riverside, CA 92521, United States

As the fast energy demand hiking and the significant environmental concerns, alternative energy is receiving more and more both research and industrial focus. Solar energy is viewed as one of the most promising candidates considering its green, sustainable, and abundant characters. Here we report a facile strategy to fabricate TiO2 three-dimensional nanowire array on flexible substrates. Unlike the pristine TiO2, which is only active under UV irradiation, the as-prepared partially reduced TiO2 shows strong visible light response, which makes it a good photoanode for visible light photoelectrochemical water splitting. Moreover, this strategy is proved to be a versatile method to fabricate three-dimensional TiO2 nanowire array on various flexible substrates.

322. Converting light into mechanical work using molecular crystal nanostructures

Chris Bardeen christob@ucr.edu

Taehyung Kimi. Chemistry, U. California, Riverside, Riverside, CA 92521, United States

Nanostructures that undergo well-defined shape changes when exposed to light could have applications as actuators or as components of nanoscale machines. We have investigated several classes of molecular photoreactions, including photodimerization and trans-cis isomerization, in order to characterize how molecular-scale chemical changes can drive micro-scale mechanical motions and deformations in shaped molecular crystals. Using a variety of methods, we prepare different classes of single crystal shapes, including nanowires, micro-ribbons, and micro-needles, all composed of photoreactive molecules. Depending on the nature of the photochemical reaction, the shape of the crystal, and the orientation of the molecules within the shaped crystal, different types of motions can be induced by photoexcitation, including expansion, bending, twisting, and curling.

323. Electrochemical measurements on colloidal TiO2 nanoparticles

Mario A Alpuche-Aviles malpuche@unr.edu

Ashantha Fernando, Suman Parajuli. Department of Chemistry, University of Nevada, Reno, Reno, Nevada 89557, United States

We propose electrochemical methods to study colloidal nanoparticles for measurements of kinetic properties of metal oxide nanoparticles (NPs). We present our studies on the photocatalytic properties of colloidal TiO2 nanoparticles. The measurements are made from nanoparticles suspended in MeOH while they interact with a working electrode. The particles are suspended in MeOH, a hole scavenger, under constant irradiation. Upon interaction with a metal electrode, discrete current steps are observed that are related to the rate of MeOH photoxidation by individual NPs. We discuss the frequency of collision of individual NPs and our advances on the calculation of photoxidation rates of individual NPs.

324. Effect of micellization on conductivity enhancement and surface charging in nonpolar media

James W. Schneider schneider@cmu.edu

Yun-Hsuan Chu, Lisa D'Costa, Benjamin Yezer, Paul J. Sides, Dennis C. Prieve. Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890, United States

Enhancement of electrical conductivity in nonpolar media is required for the safe delivery of hydrocarbon fuels, controlled electrophoresis of nonpolar pigment particles in display devices, and a growing list of applications in next-generation fuel cells. Historically, this enhancement has been achieved using compounds that form inverted micelles. By a mechanism known as disproportionation, these micelles dynamically acquire charge and act as charge carriers. A second, less well-studied class of organic compounds performs the same function without forming micelles. Here, we will present measurements of conductivity in nonpolar solvents in the presence of both types of materials and compare the observations to predictions made by the disproportionation model.

325. Surfactant induced charging of PMMA in nonpolar solvents

Gregory N. Smith1 gregory.smith@bristol.ac.uk

Sarah E. Rogers2, Roger Kemp3, Julian Eastoe1. (1) School of Chemistry, University of Bristol, Bristol, United Kingdom (2) ISIS-STFC, Rutherford Appleton Laboratory, Chilton, Oxon OX11 0QX, United Kingdom (3) Merck Chemicals Ltd, Southampton, United Kingdom

Charges in nonpolar solvents are not as easily stabilized as in polar media but are important in technologies such as electrophoretic displays. Poly(methyl methacrylate) (PMMA) spheres sterically-stabilized with poly(12-hydroxystearic acid) graft copolymer (PHSA) can be charged in organic solvents using sodium dioctylsulfosuccinate (AOT). It is unclear whether AOT adsorbs on the surface as aggregates or in the stabilizer layer as monomers. Contrast-variation small-angle neutron scattering has been employed to understand the interaction between surfactants and polymer surfaces. Solutions of PHSA have been prepared in dodecane, where it forms micelles, with AOT to simplify the system. Scattering profiles arising from PHSA contrast indicate that AOT does not significantly alter the PHSA micelles. On the other hand, when contrast arises from AOT, the scattering profile indicates that AOT surfactant penetrates throughout the stabilizer layer as monomers, rather than adsorbing on the surface as micelles.

326. Diffusiophoresis arising from multiple ions

Darrell Velegol velegol@psu.edu

Tso-Yi Chiang, Department of Chemical Engineering, Penn State University, University Park, PA 16802, United States

The movement of charged particles occurs in a salt gradient by the mechanism of diffusiophoresis. Recently, our lab has reported the diffusioosmotic flow from calcium carbonate (CaCO3) micropumps which results from the dissolution of CaCO3 in water. This dissolution generates three primary ions: Ca2+, HCO3-, and OH-. However, current models for the diffusiophoretic velocity have been derived only for charged particles in a Z:Z electrolyte at steady state, with ß = (D+ - D-)/(D+ + D-) describing the induced electric field due to the difference in diffusion coefficients between the two ions. With three ions present in our system, the ß term needs to be modified. In this talk, we present a model for the time-dependent diffusiophoretic velocity involving multiple ions. The results from our model show good agreement with our experimental data, and the calculations also suggest strategies for obtaining large diffusiophoretic transport rates.

327. Effects of Image Charges on Double Layer Structure and Forces

Rui Wang wangrui@caltech.edu

Zhen-Gang Wang. Department of Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States

The study of the electrical double layer lies at the heart of soft matter physics and biophysics. Here, we address the effects of the image charges on the double layer structure and forces using a weak coupling theory. For electrolyte solutions between two neutral plates, we show that depletion of the salt ions by the image charge repulsion results in short-range attractive and long-range repulsive forces. If cations and anions are of different valency, the asymmetric depletion leads to the formation of an induced electrical double layer. In comparison to a 1:1 electrolyte solution, both the attractive and the repulsive parts of the interaction are stronger for the 2:1 electrolyte solution. For two charged plates, the competition between the surface charge and the image charge effect can give rise to like-charge attraction and charge inversion. These results are in stark contrast with predictions from the Poisson-Boltzmann theory.

328. Irreversible electrostatic adsorption of silica nanoparticles at solid-liquid interface

Xue Li xli@che.ccny.cuny.edu

Olivia Niitsoo, Alexander Couzis. Department of Chemical Engineering, The City College of New York, New York, NY 10031, United States

Adsorption process has been widely studied and is well understood theoretically within the framework of the random sequential adsorption (RSA) model based on the assumption of irreversible adsorption. However, there is little experimental data accessible concerning the adsorption at solid-liquid interfaces, which provides detailed information about the structural arrangement of NPs and stability of the adsorbed particles, arising from the irreversibility. In this work, we exploited the irreversibility of electrostatically driven adsorption of NPs uniquely by employing the Ag@SiO2 NPs as tracking agent. In our study we used SiO2 NPs for the formation of the first layer of electrostatically adsorbed films onto amino-functionalized silicon wafer substrates. Subsequently, the substrate with adsorbed SiO2 on top was exposed to Ag@SiO2 suspension. Adsorption time was varied from 1min to one week so as to obtain well understanding of the process irreversibility. Direct SEM observation was employed followed a carefully selected set of experiments.

329. Surface charge of gold-water and gas-water interfaces: Surface chemistry surprises

Rico F Tabor1,2 rico.tabor@monash.edu

Franz Grieser2, Derek YC Chan2, Raymond R Dagastine2. (1) School of Chemistry, Monash University, Clayton, Victoria 3800, Australia (2) Particulate Fluids Processing Centre, University of Melbourne, Parkville, Victoria 3010, Australia

Capturing a bubble with the atomic force microscope, we probed interactions between bubbles of different gases and gold surfaces, mapping the pH-dependent surface charge. For air bubbles, charge is modified significantly by the presence of dissolved carbon dioxide, as seen by comparison with pure, inert gases. Using charged air bubbles as probes, we measured the surface charge of gold as a function of surface oxidation, showing a significant shift in the isoelectric point and surface chemical properties.

330. Self-Dispersing drug carriers for pulmonary delivery

Stephen Garoff2,5 sg2e@andrew.cmu.edu

Amsul Khanal1,2, Ramankur Sharma2,3, Timothy E Corcoran1,4,Ellen R Swanson x6, Todd M Przybycien1,2,3, Robert D Tilton1,2,3. (1) Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States (2) Center for Complex Fluids Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States (3) Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States (4) Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, United States (5) Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States (6) Department of Mathematics, Centre College, Danville, Kentucky 40422, United States

Present aerosolized drug delivery techniques to the lung rely entirely on aerodynamic mechanisms to disperse and distribute medications. Mucus blockages and unusual aerodynamics associated with obstructive diseases limit the distribution of these medications throughout the lung, limiting their efficacy. We are developing self-dispersing aerosol drug carriers by adding surfactants to drug formulations. Surfactants induce Marangoni flows that can enhance spreading after deposition along the airway surface liquid (ASL). We focus on relationships between surfactant compositions and final spread area of drops post-deposition. Microliter sized drops containing surfactants show enhanced spreading over saline control when depositing onto ASL mimicking aqueous polymer subphases. Imaging of individual micron-sized surfactant aerosol droplets also show enhanced spreading and delayed coalescence after deposition. Extent of spreading of surfactant aerosol on polymer subphases confined to tubes mimicking lung airways is also studied.

331. What makes M cells efficient at the uptake of invasive microbes? A role for microvilli at the mucosal barrier

Kaila M. Bennett1,2 kbenn001@ucr.edu

Sharon L. Walker3, David D. Lo2. (1) Department of Bioengineering, University of California, Riverside, Riverside, California 92521, United States (2) Division of Biomedical Sciences, University of California Riverside, Riverside, California 92521, United States (3) Department of Chemical and Environmental engineering, University of California Riverside, Riverside, California 92521, United States

Microvilli are ubiquitously expressed on polarized epithelial cells and play a key role in generating a physical barrier at mucosal sites. We report a function for microvilli in early pathogenic invasion that has previously been overlooked. Pathogens are charged species and most infect the host at the mucosal epithelial barrier, suggesting that the charge properties of apical microvilli may play crucial role in curtailing bacterial colonization. We found that uptake of a variety of microbes was increased in Caco-2BBe cells engineered to lack microvilli. This preference for microvilli-minus cells showed a linear relationship with the surface charge (zeta potential) of the microbial particles, consistent with an electrostatic mechanism. Moreover, the effect was retained under dynamic flow conditions. This study illustrates the importance of charge for bacterial invasion, and may help to identify better vaccine delivery strategies for mucosal immunization.

332. Adsorptive and covalent modifications of colloidal magnetic nanoferrites for targeted drug delivery systems

Pawel Krysinski1 pakrys@chem.uw.edu.pl

Krzysztof Nawara1, Anna M Nowicka1, Mikolaj Donten1, Zbigniew Stojek1, Ewa Augustin2, Zofia Mazerska2. (1) Department of Chemistry, University of Warsaw, Warsaw, Poland (2) Department of Pharmaceutical Technology and Biochemistry, Gdansk University of Technology, Gdansk, Poland

In the past decade, the synthesis of magnetic, colloidal nanostructures of various chemical and physical behavior has been intensively developed for many technological and medical applications, such as contrast increase of MRI, bioaffinity assays and targeted drug delivery. Keeping in mind the latter application, we synthesized nanoferrites of different chemical composition and magnetic behavior and then we focused on the two modes of surface modifications of such nanoferrites, namely: adsorptive and covalent binding of doxorubicin – a potent anti-cancer drug. This approach gave us a drug-magnetic nanoparticle conjugate. Both modifications provide stabilization of the colloid, endowing also its surface with functional groups suitable for further tailoring, e.g., modifying the hydrophilic/hydrophobic balance. For both cases the drug load and its efficiency were monitored by means of spectrofluorometry, electrochemistry and UV-VIS spectroscopy. Additionally, the drug release profiles (where applicable) and the nanoferrite-drug conjugate effect on selected tumor cell cultures were monitored.

333. Physiological properties of polymer brush-afforded nanoparticles prepared by surface-initiated living radical polymerization

Kohji Ohno1 ohno@scl.kyoto-u.ac.jp

Yoshinobu Tsujii1, Yasuhiko Tabata2. (1) Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan (2) Institute for Frontier Medical Sciences, Kyoto University, Sakyo, Kyoto 606-8507, Japan

The physiological properties of polymer brush-afforded silica particles prepared by surface-initiated living radical polymerization were investigated in terms of the circulation lifetime in the blood and distribution in tissues. Hydrophilic polymers consisting mainly of poly(poly(ethylene glycol) methyl ether methacrylate) were grafted onto silica particles by surface-initiated atom transfer radical polymerization that was mediated by a copper complex to produce hairy hybrid particles. The hybrid particles were injected intravenously into mice to systematically investigate their blood clearance and body distribution. It was revealed that the structural features of the hybrid particles significantly affected their in vivo pharmacokinetics.

334. Photodynamics of colloidal aggregates of sunscreen molecules in water

Chris Bardeen christob@ucr.edu

Kerry Hanson. Chemistry, U. California, Riverside, Riverside, CA 92521, United States

Sunscreens are an important strategy for the prevention of photoaging and skin cancer. The photochemistry of the UV filter octylmethoxycinnamate is investigated in different environments under simulated UVA+UVB solar irradiation. In dilute solution, the molecule undergoes photoisomerization between trans-OMC and cis-OMC until a photostationary state is achieved. A small decrease in the absorptivity of the UV filter results from the lower molar absorptivity of the cis-isomer. In contrast, when OMC is aggregated in aqueous suspensions, it does not achieve a photostationary state but instead degrades irreversibly via intermolecular cycloaddition and intra-molecular photo-Fries reactions. The data show that the photoresponse of OMC depends on its environment and is qualitatively different when the molecule is aggregated in colloidal suspension in water. Our results suggest that the photochemistry that occurs in colloids of this molecule must be taken into account in the design of commercial sunscreens.

335. Development of Anti-HER2 Functionalized Optical Viral Ghosts for Targeting of Ovarian Cancer Cells

Yadir Guerrero1 yguer002@ucr.edu

Baharak Bahmani1, Sheela P. Singh2, Valentine Vullev1, Vikas Kundra2, Bahman Anvari1. (1) Department of Bioengineering, University of California Riverside, Riverside, CA 92521, United States (2) MD Anderson Cancer Center, University of Texas, Houston, TX 77030, United States

Our group has constructed a new type of virus mimicking nanoconstruct from genome-depleted plant infecting brome mosaic virus (BMV) that encapsulates FDA-approved near infrared indocyanine green1. We refer to these nanoconstructs as optical viral ghosts (OVGs) since they lack viral RNA. One of our areas of interest is the theranostic application of OVGs for real-time intraoperative NIR fluorescence imaging and photodestruction of small peritoneal ovarian tumor nodules. We functionalize the OVGs with anti-HER-2 monoclonal antibodies using PEG linkers and reductive amination methods. We present here the work done to develop the functionalization parameters, as well as the optimization of photophysical parameters. We made use of the SKOV-3 cell line and the OVCAR-3 (high and low-HER-2 expression respectively) to verify the functionality and uptake dynamics of our surface functionalization. Our work suggests that our optimized OVGs are capable of discriminately imaging high HER-2 expressing cells.

336. Geometry-controlled interface localization-delocalization transition in block copolymers

Marcus Mueller mmueller@theorie.physik.uni-goettingen.de

Institute for Theoretical Physics, Georg-August University, Gottingen, Lower Saxony 37077, Germany

Lamellar copolymers confined into a film of thickness D by two stripe-patterned surfaces, which are rotated against each other, form lamellar domains that register and align with the respective chemical surface patterns. The two domains of thickness x and D-x are separated by an interface that resembles a twist grain boundary. At small twist angles or strong selectivity of the surface patterns, this interface fluctuates around the middle of the film, while the interface is localized at one of the surfaces in the opposite limit. These two morphologies are separated by an interface localization-delocalization transition (ILDT) that can be controlled by the twist angle a. For thin films, we find a second-order ILDT while the ILDT is of first-order for large D. A phenomenological interface Hamiltonian is used to relate the findings to the ILDT of symmetric mixtures and the predictions are confirmed by molecular simulation.

337. Elastic Property and Line Tension of Self-Assembled Membranes

An-Chang Shi shi@mcmaster.ca

Department of Physics and Astronomy, McMaster University, Ontario, Canada

The elastic properties, include the bending rigidity, the Gaussian modulus, two fourth-order membrane moduli, and the line tension, of a bilayer membrane are examined theoretically using a microscopic model of flexible amphiphilic chains dissolved in hydrophilic polymer solvents. We systematically investigate the dependency of these phenomenological quantities on the molecular property of the amphiphilic chain. In particular, we examined the region of validity of the linear elastic theory.

338. Reactive Wetting at Planar Interfaces

Frank van Swol fbvansw@sandia.gov

Computational Materials Department, Sandia National Laboratories, Albuquerque, NM 87059, United States

We report on the phenomenon of reactive wetting at a planar wall-fluid interface. The term reactive wetting is used to describe wetting behavior in the presence of compositional changes in the fluid phase. In practice, compositional changes can be due to a variety of phenomena including a chemical surface reaction, dissolution of a solid phase into a fluid phase, or the (re-)partioning of a species between the phases involved. The compositional changes at the interface are reflected in changes in the interfacial free energy and contact angles. The latter directly controls the spreading of a droplet and the capillary flow that occurs during infiltration of porous structures (e.g., as described by the Washburn equation). We use molecular simulation methods to explore the basic phenomenon of reactive wetting and focus on key issues controlling spreading and infiltration.

339. Liquid bridge stability with a free contact line: Catenoid limit

Amir Akbari1 amir.akbari.mcg@gmail.com

Reghan J. Hill1, Theodorus G.M. van de Ven2. (1) Chemical Engineering, McGill University, Montreal, Quebec, Canada (2) Chemistry, McGill University, Montreal, Quebec, Canada

Contact drop dispensing is central to many small-scale applications, such as direct scanning probe lithography and micromachined fountain-pen techniques. Accurate and controllable dispensing required for nanometer resolved surface patterning hinges on the stability and breakup of liquid bridges. Here, we study the stability of axisymmetric liquid bridges pinned at one contact line with the other free to move on a substrate when the capillary pressure is very small or asymptotically zero. The stability region is represented with respect to the bridge volume, slenderness, and contact angle. From a numerical perspective, this problem is ill-conditioned for very small, but not asymptotically zero, pressures. To resolve this issue, a perturbation based conditioning technique is proposed and applied to construct the stability phase diagram for liquid bridges in the catenoid neighbourhood. This also provides insights into the complex structure of the stability region in the catenoid limit.

340. Dynamic wetting of water nano-droplets with non-surfactant and Janus nanoparticles: a molecular dynamics study

Ying Sun2 ysun@coe.drexel.edu

Gui Lu1, Yuanyuan Duan1. (1) Department of thermal engineering, Tsinghua University, Beijing, Beijing 100084, China (2) Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, Pennsylvania 19104, United States

The wettability of nanofluids is of particular interest to microfluidic systems, such as microbial chip and MEMS, in which surface tension plays an important role. In this paper, the dynamic spreading of water nano-droplets with non-surfactant and Janus nanoparticles is examined via molecular dynamics simulations. The effects of particle volume fraction, wettibility, and shape on wetting kinetics and contact line mobility are discussed. The addition of non-surfactant nanoparticles hinders rather than enhancing spreading during the nano-second process, as a result of increasing surface tension and liquid-solid friction. Incapability to assemble among nanoparticles during wetting attributes to the discrepancy of wetting kinetics of a nano-sized droplet compared to those observed in macroscopic experiments. The wetting kinetics of water droplets containing Janus nanoparticles is also explored.

341. Coil-globule transition of a strongly-charged polyelectrolyte chain in a salt-free solvent: A Replica Exchange Monte Carlo Study

Baohui Li baohui@nankai.edu.cn

School of Physics, Nankai University, Tianjin, China

The conformation transitions and the nature of the coil-globule transition of a strongly-charged polyelectrolyte chain in a salt-free solvent are studied using replica-exchange Monte-Carlo simulations. The results reveal that the chain can assume a variety of conformations and it undergoes two phase transitions upon cooling. One transition is identified as a continuous counterion condensation transition whereas the other as a first-order coil-globule transition. In the globular state, the counterions and the charged chain segments are densely packed into three-dimensional Wigner crystals. Based on an analysis of finite chain length effect, it is deduced that in the thermodynamic limit of infinitely large chain length, the coil-globule transition may remain to be first-order, and the chain length dependence of the transition temperature are obtained for systems with several ion concentrations.

342. Photo-rheological response of aqueous wormlike micelles with photocleavable surfactant

Hideki Sakai1 hisakai@rs.noda.tus.ac.jp

Shohei Aikawa1, Kaori Fukuda1, Shrestha G Rekha1, Takeshi Endo1, Kanjiro Torigoe1, Kenichi Sakai1, Kazutami Sakamoto2, Masahiko Abe1. (1) Faculty of Science and Technology, Tokyo University of Science, Noda, Chiba 278-8510, Japan (2) Faculty of Pharmacy, Chiba Institute of Science, Choshi, Chiba 288-0025, Japan

Recently, we have reported a new cinnamic acid-type photo-cleavable surfactant, C4-C-N-PEG9 that experiences a photo-cleavage through UV-induced cyclization in aqueous solution, yielding a coumarin derivative and an aminated polyoxyethylene compound1). Here, we have studied the effects of C4-C-N-PEG9 on the photorheological behavior of viscoelastic wormlike micelles formed by aqueous mixture of nonionic surfactants, polyoxyethylene phytosterol ether (PhyEO20) and tetraoxyethylene dodecyl ether (C12EO4). When C4-C-N-PEG9 is added to the viscous, non-Newtonian PhyEO20/C12EO4/H2O fluid, a decrease in viscosity is observed, while upon UV irradiation C4-C-N-PEG9 added solution regains the viscosity. It increases by 200 times, suggesting a modulation in micellar shape and size. The UV-Vis spectroscopy and HPLC measurements confirm that the trans-C4-C-N-PEG9 with large head group and its photodecomposition to form less surface-active coumarin derivative and an aminated polyoxyethylene compound are responsible for different rheological behavior. Reference: 1) Sakai, H., et al., J. Colloid and Interface Sci., 2012 , 376, 160–164.

343. Dual pH-triggered physical gels prepared from self-assembly in mixed dispersions of oppositely charged pH-responsive microgels

Brian R Saunders1 brian.saunders@manchester.ac.uk

James McParlane1, Damien Dupin2, Stephen P Armes2. (1) School of Materials, University of Manchester, Manchester, England M13 9PL, United Kingdom (2) Department of Chemistry, University of Sheffield, Sheffield, England S3 7HF, United Kingdom

We investigate pH-triggered physical gel (soft particle glass) formation from concentrated mixed dispersions of heteroaggregated pH-responsive microgels[1]. The two microgels studied are poly(ethyl acrylate / methacrylic acid / 1, 4-butanediol diacrylate) (referred to as PEAMAA) and poly(2-vinylpyridine / divinylbenzene) (referred to as PVP). The anionic PEAMAA particles are alkali-swellable and the cationic PVP particles are acid-swellable. Concentrated homodispersions formed physical gels at either low pH (PVP) or high pH (PEAMAA). Concentrated PEAMAA / PVP heterodispersions formed physical gels at both low and high pH. At low pH the collapsed PEAMAA particles greatly increased the storage modulus (G') and also the critical yield strain of the mixed PEAMAA / PVP gels compared to the parent PVP homoparticle gel. A remarkably high G' value of 0.12 MPa was obtained for a mixed PEAMAA / PVP gel containing 90 vol.% water. [1] McParlane et al., Soft Matter, 8, 6239, 2012

344. Surface patterning of conjugated polyelectrolytes through self-assembly with lipid membrane domains

Darryl Y Sasaki1 dysasak@sandia.gov

Carl C Hayden2, Hsing-Lin Wang3, Atul N Parikh4, Andrew P Shreve5. (1) Department of Biotechnology and Bioengineering, Sandia National Laboratories, Livermore, CA 94551, United States (2) Department of Combustion Chemistry, Sandia National Laboratories, Livermore, CA 94551, United States (3) Department of Physical Chemistry and Applied Spectroscopy, Los Alamos National Laboratory, Los Alamos, NM 87545, United States (4) Department of Bioengineering, University of California at Davis, Davis, CA 95616, United States (5) Department of Biomedical Engineering, University of New Mexico, Albuquerque, NM 87131, United States

Conjugated polyelectrolytes (CPEs) are promising materials for generating optoelectronics devices under environmentally-friendly processing conditions, but challenges remain to develop methods to define lateral features for improved junction interfaces and direct optoelectronic pathways. We describe here the potential to use a bottom up approach that employs self-assembly in lipid membranes to form structures which template the selective adsorption of CPEs. Phase separation of gel-phase anionic lipids and fluid phase phosphocholine lipids allowed the formation of negatively charged domain assemblies that selectively adsorb a cationic conjugated polyelectrolyte. Spectroscopic and topological studies found the polymer strongly binds to the membrane resulting in an enhancement in fluorescence intensity due to attenuated pathways for quenching and vibrational relaxation. In supported lipid bilayers we also show that predefined features, such as straight lines, of gel-phase domains can be directed to form upon etched patterns on the substrate thus providing potential routes towards novel optoelectronic architectures.

345. Monitoring intermolecular reactions on nanoparticle-modified supported lipid bilayer platforms

Young Kwang Lee glolee@snu.ac.kr

Sungi Kim, Jwa-Min Nam. Department of Chemistry, Seoul National University, Seoul, Republic of Korea

Supported lipid bilayer (SLB) has been considered to be a very attractive platform as it preserves many of biologically important features of native cell membranes, including lateral fluidity. This model membrane system simplifies the complex circumstances and reproduces various membrane phenomena. In order to completely grasp and analyze the biological processes on SLB, direct visualization and tracking of membrane-associated components are highly desirable. Here, we present plasmonic nanoparticle-modified SLB platforms to observe intermolecular reactions between membrane-tethered components. Metal nanoparticles efficiently scatter incident light at their specific resonance wavelength and free to photobleaching and blinking. When the DNA-modified metal nanoparticles are tethered to a fluid lipid bilayer in a laterally mobile fashion, two-dimensional diffusion trajectories can be recorded with a dark-field microscopy. In situ monitoring of the assembly and disassembly processes at single nanoparticle resolution allows for studying general biological reactions and membrane reactions as well.

346. Tunable self-assembled nanoparticle assemblies with activity in visible wavelengths

Zhiyuan Huang1 zhuan009@ucr.edu

Monica Marks2, Ming Lee Tang1. (1) Department of Chemistry, University of California- Riverside, Riverside, California 92507, United States (2) Department of Materials Science and Engineering, University of California- Riverside, Riverside, California 92507, United States

The interaction of light with noble metal nanoparticles can be tuned by control of their 3D arrangement. With the use of efficient organic chemical reactions, plasmonic nanoparticles are self-assembled to make metamaterials that are active at visible wavelengths. Plasmon hybridization can be tuned by varying particle size or interparticle distance. Different kinds of organic multidentate ligands are synthesized and attached to the surface of nanoparticles. Then rigid organic scaffolds are designed to secure the nanoparticles in predefined positions by self-assembly in order to manipulate and confine light. For example, chiral metamaterials can be synthesized by using asymmetrical scaffolds or different particles in different sizes. This material can be widely used in enantioselective biosensing, non-linear optics, asymmetric synthesis or surface-enhanced spectroscopies.

347. Controlled enantioselectivity in hydrogenation of ethyl pyruvate with platinum catalysts by using self-assembled monolayers

Zhihuan Weng zweng@ucr.edu

Francisco Zaera. Department of Chemistry, University of California, Riverside, Riverside, CA 92521, United States

The enantioselective hydrogenation of ethyl pyruvate over cinchona-platinum catalyst system has been intensively studied as a prototypical system for heterogeneous catalytic asymmetric hydrogenation reactions. Here we describe the preparation of highly enantioselective Pt catalysts involving the deposition of n-alkanethiol self-assembled monolayer coatings. These coatings improve the enantioselectivity of the hydrogenation of ethyl pyruvate on Pt catalysts with cinchonidine from 4.4% to 66.3% under identical reaction conditions. Although sulfur-containing species are generally considered to be indiscriminate catalyst poisons, here we show that the activity and enantioselectivity of Pt catalysts can be regulated rationally via the control of the molar ratios of capping thiol and the length of thiol tail. The behavior of thiol-coated catalysts was compared with catalyst where surface sites were modified by sulfur atoms alone. The results suggest that the morphology of the thiol tail on Pt surface plays the key role on performances of the catalysts.

348. Design, Synthesis, and Characterization of Smart and Multifunctional Hydrogels

Jie Zheng zhengj@uakron.edu

Chao Zhao, Qiang Chen, Lingyan Li. Department of Chemical and Biomolecular Engineering, The University of Akron, Akron, OH 44325, United States

We design, synthesize, characterize, and test a series of smart hydrogels with special functions for different biomedical applications. First, hybrid poly(N-hydroxyethylacrylamide) (polyHEAA)/salicylate (SA) hydrogels with integrated antifouling and antimicrobial capacities synergistically exhibit high antibacterial activity to kill both Gram (+) and Gram (-) bacteria in solution, while still maintaining high surface resistance to bacteria attachment. Both effects contribute to effective antimicrobial activity. Second, switchable poly(acrylamide) with pendant ortho ester groups hydrogels were synthesized. Upon hydrolysis of ortho ester groups in acid condition, the hydrogels enable to achieve a switchable function from protein capture to protein release. Last, we for the first time propose and demonstrate a simple, one-pot method to prepare Agar/PAM double-network hydrogels, which exhibit excellent mechanical and recoverable properties. Particularly, the resulting gels can be easily adapted to different and complex shapes for a specific application.

349. Direct visualization of step stress deformation in attractive colloidal glasses and gels

Hubert K Chan hkchan@uci.edu

Ali Mohraz. Department of Chemical Engineering, University of California, Irvine, Irvine, CA 92697, United States

The decision to incorporate soft viscoelastic materials into numerous products and technologies is often attributed to their complex rheology and deformation in response to external forces. A better understanding of the underlying physics of these events requires the ability to characterize how a material's microstructure evolves during deformation. In this work, we investigate the microstructural origins of creep deformation and yielding under constant unidirectional shear stress in dense colloidal suspensions with varying interparticle attraction strength, using a custom-built shear cell coupled to a fast-scanning confocal microscope. Particularly, we investigate at the microstructural level the load-bearing mechanisms, origins of yielding, and transient rheology of these glassy and paste-like suspensions. The role of these microstructural processes in two-step yielding and re-entrant rheology in these materials will be discussed.

350. Gel point determination thanks to microrheology

Guillermo Smart1 tisserand@formulaction.com

Christelle Tisserand2, Roland Ramsch2. (1) Formulaction Inc, Davie, Florida 33330, United States (2) Formulaction, L'Union, France

This work presents a new technique of passive microrheology for the study of the microstructure viscoelastic properties and the gel point transition for polymers and hydrogels. Passive microrheology consists of using micron sized particles to measure the local deformation of a sample resulting from the thermal energy, that is to say the Brownian motion. Our technique is based on Diffusing Wave Spectroscopy. It consists of Dynamic Light Scattering (DLS) extended to an opaque media. The determination of the Mean Square Displacement (MSD) curve enables to characterize completely the viscoelastic properties of a sample. This work presents a rescaling data processing known in rheology as time cure superposition to determine the gel point transition and gel strength parameters. Results will show the determination of the gel point versus time for yoghurt, gel point versus concentration for xanthan polymer, cross-linker concentration effect on the gel point.

351. Structure and dynamics of microemulsion networks with end-capped star polymers of low functionality.

Paula Malo de Molina1 paulamalodemolina@gmail.com

Christoph Herfurth2, André Laschewsky2,3, Michael Gradzielski4. (1) Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, CA 93106, United States (2) Institut für Chemie, Universität Potsdam, Golm, Germany (3) Fraunhofer-Institut für Angewandte Polymerforschung, Golm, Germany (4) Stranski-Laboratorium, Technische Universität Berlin, Berlin, Germany

The admixture of telechelic polymers to microemulsions allow their rheological control and their mixtures serve as network model systems where the concentration of nodes and connectivity can be tuned separately. We present a study where end-capped multi-arm polymers are the bridging elements of the network. We employed tailor-made bridging amphiphilic polymers with 2, 3, or 4 poly(N,N-dimethylacrylamide) (PDMA) end-capped arms synthesized by the RAFT procedure and nonionic oil in water microemulsion droplets with radii of 2.5-7 nm. Our results show a correlation between the interdroplet interaction, the polymer content and the polymer architecture. The elasticity of the network is correlated with the polymer architecture. DLS show increasingly complex relaxation patterns with increasing number of polymer arms. In summary, we achieve control over the rheological and dynamical properties of the micromulsions via the molecular architecture of the telechelic multi-arm polymers without interfering with the structural integrity of the droplets.

352. Probing arrested spinodal decomposition in attractive nanoemulsions en route to gelation

Yongxiang Gao yxgao@engineering.ucsb.edu

Matthew E. Helgeson. Department of Chemical Engineering, University of California Santa Barbara, Santa Barbara, California 93106, United States

We investigate the mechanism of thermogelation in attractive nanoemulsions at high volume fraction. The reversible nature of gelation allows for careful examination of intermediate states en route to gelation by combining bulk rheology with local structural and dynamical probes including scattering, differential dynamic microscopy (DDM) and microrheology. We find that gelation is accompanied by significant heterogeneity at the micron-scale, which is easily visible by optical microscopy. The observed heterogeneity exhibits correlations whose characteristic dimension grows linearly with time. Using DDM, we quantify the dynamical fluctuations of these correlations, which are well-captured by a convolution of short time diffusion and slow relaxation modes. The latter follows compressed exponential dynamics with ballistic motion above a critical length scale, and a relaxation time that scales according to hyperdiffusive dynamics. These results demonstrate that gelation proceeds via arrested spinodal decomposition, and can serve as a means to control the heterogeneous gel structure and dynamics.

353. Synthesis, crystallinity control, and photocatalysis of mesoporous TiO2 shell nanostructures

Ji Bong Joo jibongj@ucr.edu

Francisco Zaera, Yadong Yin. Department of Chemistry, UC Riverside, Riverside, CA 92507, United States

Mesoporous hollow TiO2 shell nanostructures with well controlled characteristics are highly desirable in many practical applications. In particular, they can provide high surface area, reduced diffusion resistance and improved accessibility during chemical reactions. Recently, we developed couples of novel synthetic methods for synthesis of mesoporous TiO2 shell nanostructures such as protected-calcination, partial-etching and re-calcination, and acid treatment followed by calcination processes. By changing the synthetic parameters and conditions, we precisely controlled crystalline properties as well as other physical characteristics of mesoporous TiO2 shell nanostructures. When used as photocatalysts for the degradation of Rhodamine B under UV irradiation, mesoporous TiO2 shell nanostructures show significantly improved catalytic activity. We will discuss further our synthetic methodologies, crystallinity control and photocatalytic activity of mesoporous TiO2 shell nanostructure in this presentation

354. Polystyrene-Graphene oxide Pickering emulsions for electronics

Soujanya Muralidhara1,2 Bridgette_Budhlall@uml.edu

Margaret J Sobkowicz-Kline1, Bridgette M Budhlall1,2. (1) Department of Plastics Engineering, University of Massachusetts, Lowell, MA 01854, United States (2) NSF Center for High-Rate Nanomanufacturing, University of Massachusetts, Lowell, MA 01854, United States

Here we describe the synthesis and characterization of polystyrene (PS) nanoparticles via a colloidal Pickering emulsion approach using graphene oxide (GO) as a stabilizer. GO can be used to replace conventional surfactants owing to its amphiphilic nature. Particle size and zeta potential measurements were carried out via dynamic light scattering to examine the stability of the colloids. Morphology examined by TEM showed that the GO sheets were located on the surface of the PS particles. TGA was performed to obtain additional confirmation of both GO content and structural aspects on the thermal stability of particles. The modified graphene shows good compatibility and interactions with PS to form conducting films. The electrical conductivity and resistance of the films was measured as a function of GO content. Herein we demonstrate a simple and scalable fabrication scheme based on a commodity plastic that could be useful for low-cost, macro-scale electronics.

355. Isothermal ice-crystallization kinetics in catalyst layers of proton-exchange-membrane fuel cells

Thomas J. Dursch1,2 tdursch@berkeley.edu

Gregory J. Trigub1, Jianfeng F. Liu1, Clayton J. Radke1, Adam Z. Weber2. (1) Department of Chemical and Biomolecular Engineering, University of California, Berkeley, Berkeley, CA 94720, United States (2) Environmental Energy Technology Department, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States

For successful automotive applications, proton-exchange-membrane fuel cells (PEMFCs) must permit rapid startup from subfreezing temperatures where solidified water hinders access of oxygen to catalytic sites in the cathode catalyst layer (cCL) causing cell failure. Elucidation of the mechanism(s) and kinetics of ice formation within the cCL are critical to achieving successful cell startup and to sustaining high performance at low temperatures. New isothermal DSC measurements are presented for ice-crystallization kinetics and ice-nucleation rates as functions of subcooling for four carbon-support materials, and with varying ionomer fraction and platinum loading. Using Johnson-Mehl-Avrami-Kolmogorov theory, we provide an ice-crystallization rate equation valid within cCLs. Using a simplified PEMFC continuum model, we compare ice-crystallization times and ice saturations predicted using the newly obtained rate equation to that predicted using a traditional expression (Balliet, 2008). We then identify conditions under which ice-crystallization kinetics are critical and elucidate their impact on low-temperature PEMFC operation.

356. Silicon nanoparticle and carbon nanotube composite anodes for lithium-ion batteries

Lanlan Zhong1 lzhon002@ucr.edu

Lorenzo Mangolini2. (1) Materials Science and Engineering Program, University of California, Riverside, Riverside, California 92507, United States (2) Department of Mechanical Engineering and Materials Science and Engineering Program, University of California, Riverside, Riverside, California 92507, United States

Silicon is a very promising material for anodes of lithium ion batteries. It exhibits a high theoretical capacity of 3579 mAh/g. However, during the lithiation and de-lithiation, silicon materials experience up to 300% volume change, leading to poor cyclability. Research shows that reducing the silicon particle size can mitigate this problem. Carbon nanotubes (CNTs) function well as electrode material in electrolytic cells for their high electrical conductivity and surface area. In this work, we combine silicon nanoparticles (NPs) and CNTs as anode materials. Silicon NPs are generated using a plasma-enhanced chemical vapor deposition technique, and their surface is modified with a 12-carbon long aliphatic chain to impart solubility in non-polar solvents. They are applied onto a nanotube-based layer using a wet-phase deposition technique. SEM and TEM analysis confirm that they form a conformal coating onto the nanotube surface. The composite material is tested in half-cells.

357. Bicontinuous battery electrodes derived from bijels

Jessica A Witt jawitt@uci.edu

Daniel R Mumm, Ali Mohraz. Department of Chemical Engineering and Materials Science, University Of California, Irvine, Irvine, California 92697, United States

Recent advances in battery electrode technology have shown that the ideal electrode structure consists of a three-dimensional bicontinuous arrangement of interpenetrating domains that allow for efficient electron and ion transport, as well as a large energy storage capacity. Here we present a novel method to produce this unique morphology through the utilization of a soft matter template derived from bicontinuous interfacially jammed emulsion gels (bijels). These non-equilibrium colloidal materials inherently have a bicontinuous microstructure, where interpenetrating domains of two immiscible fluids are kinetically arrested through jamming of colloidal particles at the fluid-fluid interface during spinodal decomposition. The characteristic size of the fluid domains is controlled solely through the overall colloid volume fraction. In this talk, we outline the approach for the synthesis of composite battery electrode materials using this new class of soft colloidal materials, and provide examples of electrochemically-active composites that we have synthesized through this route.

358. Silicon-carbon composite Li-ion anode mateials via seeded dispersion polymerization of acrylonitrile

Juchen Guo jguo@engr.ucr.edu

Department of Chemical and Environmental Engineering, UC Riverside, Riverside, CA 92521, United States

This presentation introduces a new methodology to synthesize nanocomposites in which silicon nanoparticles are uniformly dispersed in a mesoporous carbon host. The composite is synthesized through copolymerization of acrylonitrile and silicon nanoparticles functionalized with vinyl groups which serve as seeds for free radical dispersion polymerization, followed by carbonization of the PAN coating/network. The method yields nanocomposites with high reversible capacities and stable cycling performance, which may be due to improved structural stability of the silicon-carbon composite and the improved bonding between silicon and the carbon host.

359. New method for determining the Hamaker constant of a solid with atomic force microscopy

David S Corti1 dscorti@purdue.edu

Jiannan Dong1, Yan Zhao2, Hou T. Ng2, Elias I Franses1. (1) School of Chemical Engineering, Purdue Univeristy, West Lafayette, Indiana 47907-2100, United States (2) Printing and Content Delivery Lab, HP Labs, Hewlett-Packard Co., Palo Alto, CA 94304-1126, United States

We develop an improved procedure for determining the Hamaker constant, A, of a solid using atomic force microscopy (AFM) which acknowledges explicitly that the tip motion is dynamic, and not quasi-static. While still invoking a quasi-static model to interpret the dynamic data, a novel energy-based iterative scheme is introduced, in which an apparent Hamaker constant, Aapp, is determined from the dynamic data and the quasi-static model. Aapp depends on the cantilever speed, vc, and the spatial resolution d of the data points, and converges to the quasi-static value of A as vc ? 0. We test the method using simulated data generated from the dynamic curve of the tip motion, and show that small values of d and low cantilever speeds yield the most accurate estimates of A. Finally, the new method is applied to dynamic AFM data for a model system of glass (amorphous SiO2).

360. Variable wavenumber cutoff for modelling van der Waals dispersion energy

Nadia A. Shardt1,2 nshardt@ualberta.ca

Janet A. W. Elliott1 janet.elliott@ualberta.ca

Subir Bhattacharjee2. (1) Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 2V4, Canada (2) Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta T6G 2G8, Canada

Understanding the fundamental principles underlying van der Waals interactions is essential in the field of colloids and interfacial phenomena. The traditional Lifshitz model encounters a divergence in energy as the distance between two semi-infinite plates approaches zero. A distance cutoff was first applied to address this divergence, and a wavenumber cutoff model has recently been introduced by White. An assumption was made that this wavenumber cutoff is constant across a set of three materials independent of which materials are interacting or intervening. We assess the validity of this assumption by considering a system consisting of decane, water, and air. Taking values of interfacial tension from literature, we determine the wavenumber cutoff for all combinations of these substances and find that the cutoff values vary within an order of magnitude. The interaction energy of each system is plotted as predicted by the Lifshitz, constant wavenumber cutoff, and system-specific wavenumber cutoff models.

 

360. Variable wavenumber cutoff for modelling van der Waals dispersion energy

Nadia A. Shardt1,2 nshardt@ualberta.ca

Janet A. W. Elliott1 janet.elliott@ualberta.ca

Subir Bhattacharjee2. (1) Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 2V4, Canada (2) Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta T6G 2G8, Canada

Understanding the fundamental principles underlying van der Waals interactions is essential in the field of colloids and interfacial phenomena. The traditional Lifshitz model encounters a divergence in energy as the distance between two semi-infinite plates approaches zero. A distance cutoff was first applied to address this divergence, and a wavenumber cutoff model has recently been introduced by White. An assumption was made that this wavenumber cutoff is constant across a set of three materials independent of which materials are interacting or intervening. We assess the validity of this assumption by considering a system consisting of decane, water, and air. Taking values of interfacial tension from literature, we determine the wavenumber cutoff for all combinations of these substances and find that the cutoff values vary within an order of magnitude. The interaction energy of each system is plotted as predicted by the Lifshitz, constant wavenumber cutoff, and system-specific wavenumber cutoff models.

 

361. Single Molecule Measurements Using Correlation Force Spectroscopy

Milad Radiom1 mradiom@vt.edu

Janet A. W. Elliott1 janet.elliott@ualberta.ca

Brian Robbins2, John Walz3, Mark Paul2, William Ducker1. (1) Department of Chemical Engineering, Virginia Tech, Blacksburg, VA 24061-0131, United States (2) Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA 24061-0131, United States (3) Department of Chemical and Materials Engineering, University of Kentucky, Lexington, KY 40506, United States

Thermal noise represents a fundamental limit in force measurements. We developed a new technique using two AFM cantilevers that has lower thermal noise than single-cantilever measurements. We achieve this by measuring correlated thermal motions of two closely spaced cantilevers. In addition to comparing to the single-cantilever measurements, the use of two cantilevers decreases interferences from hydrodynamic fluid damping and van der Waals forces acting on an AFM probe. Analysis of the correlated motions reveals molecular damping, a parameter that is not sensed with conventional (pulling) AFM single molecule force spectroscopy. When a molecule is straddled between the two cantilevers, the correlation arises from the solvent coupling as well as stiffness and damping of the molecule. We will describe the technique of correlation force spectroscopy and measurements of the mechanical properties of double stranded DNA.

 

362. Hydrodynamic boundary condition of water on hydrophilic and hydrophobic surfaces

Hans-Juergen Butt1 butt@mpip-mainz.mpg.de

David Schaeffel1, Stoyan Yordanov1,2, Marcus Schmelzeisen1, Tetsuya Yamamoto1,3, Michael Kappl1, Roman Schmitz1, Burkhard Duenweg1,4,Kaloian Koynov1. (1) Deparment of Experimental Physics, Max Planck Institute for Polymer Research, Mainz, Germany (2) Department of Chemistry, KU Leuven, Leuven, Belgium (3) Department of Chemistry and Chemical Engineering, Hiroshima University, Higashi-Hiroshima, Japan (4) Department of Chemical Engineering, Monash University, Melbourne, Australia

By combining total internal reflection cross-correlations spectroscopy (TIR-FCCS) with Brownian dynamics simulations we were able to measure the hydrodynamic boundary condition of water flowing over a smooth solid surface with unprecedented accuracy. We analyzed the flow of aqueous electrolyte over hydrophilic glass and glass coated with a layer of PDMS (advancing contact angle T = 108°) or perfluorosilane (T = 113°). Within an error of less than 10 nm the slip length was indistinguishable from zero on all surfaces. S. Yordanov, A. Best, H.-J. Butt & K. Koynov, Optics Express 2009 , 23, 21149. R. Schmitz, S. Yordanov, H.-J. Butt, K. Koynov & B. Dünweg, Phys. Rev. E 2011 , 84 , 066306. D. Schaeffel, S. Yordanov, M. Schmelzeisen, T. Yamamoto, M. Kappl, K. Koynov, B. Dünweg & H.-J. Butt2013 , submitted.

 

363. Parametric Investigation of Microprinting Resolution and Stability Using Polymeric Aqueous Biphasic Systems

David Petrak dp34@zips.uakron.edu

Hossein Tavana. Biomedical Engineering, The University of Akron, Akron, Ohio 4, United States

Using immiscible aqueous solutions of two polymers, nanoliters of the reagent-containing aqueous phase can be patterned on a biological surface immersed within the second aqueous phase. Our parametric study shows that the resolution and stability of liquid micropatterning closely depends on polymer concentration, printing tool dimensions, speed, and loaded volume, and the surface characteristics. An automated three-dimensional motorized system is developed to systematically study the effect of each variable. We find that the resolution of microprinted linear features is limited by Rayleigh-type instability due to local, sharp changes in the radii of curvature of microprinted features, resulting in breakage of patterns into droplets. Understanding this behavior and parametric optimization of the printing technique has allowed generating stable linear patterns of cells on different types of surfaces, with a resolution of few hundred microns. This technology is useful for a number of applications including engineering three-dimensional tissue constructs.

 

364. Short peptide of BMP-7 and nanophase hydroxyapatite-PLGA composite enhance human mesenchymal stem cell osteogenic differentiation

Jaclyn Y Lock1 jlock003@ucr.edu

Huinan Liu1,2. (1) Department of Bioengineering, University of California, Riverside, Riverside, CA 92521, United States (2) Materials Science and Engineering Program, University of California, Riverside, Riverside, CA 92521, United States

Controlling stem cell function (e.g. adhesion and differentiation) is essential for improving tissue regeneration. Nanomaterials offer unique advantages for tissue engineering and drug delivery applications due to their biomimetic characteristics and unique biological and mechanical properties. We investigated the effects of nano-hydroxyapatite, nano-hydroxyapatite-polylactide-co-glycolide (PLGA) composites, and a bone morphogenetic protein (BMP-7)-derived short peptide (DIF-7c) on osteogenic differentiation of human mesenchymal stem cells (hMSCs). We selected DIF-7c peptide as a model peptide due to its ability to promote osteoblast differentiation. Results showed that nanophase hydroxyapatite alone and nanophase hydroxyapatite-PLGA composite promoted osteogenic differentiation (i.e. calcium deposition and alkaline phosphatase activity) of hMSCs similarly to direct injection of the DIF-7c peptide into the culture media. And the nanophase hydroxyapatite-PLGA composite had higher hMSC adhesion than the PLGA scaffold alone. Overall, the nanophase hydroxyapatite-PLGA composite demonstrated promising in vitro results to direct osteogenic differentiation of hMSCs.

 

365. Stimuli-responsive poly(amino acid)s nanogels for drug delivery

Jong-Duk Kim kjd@kaist.ac.kr

Chan Woo Park Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology, 373-1 Guseong dong, Yuseong Ku, Daejeon, Republic of Korea

In this presentation, we report cross-linked poly(amino acid)s nanoparticles based delivery of therapeutic agents and imaging agents. We developed the cross-linkable amphiphilic copolymer platform of poly(succinimide)-co-PEG (PSI-co-PEG). A water-insoluble PSI rapidly reacts with primary or secondary amine-containing functional compounds. Hence, the PSI was introduced as a cross-linkable unit, and disulfide cross-linked micelles prepared by cross-linking of PSI-g-PEG micelles using cystamine cross-linkers. Nanogel was prepared by chemical conversion of residual PSI units into hydrophilic poly(aspartic acid) (PAsp). A positively charged anticancer drug, doxorubicin, was successfully entrapped within the PAsp core by electrostatic interaction. The disulfide cross-linked nanogels showed disruption of spherical structure at the reductive environment because of the cleavage of disulfide bonds, and the doxorubicin loaded nanogels showed the improved anticancer effect in vitro. Furthermore, cross-linked PSI-g-PEG coated iron oxide nanoparticles were prepared for the MR imaging of tumor.

 

366. Bioconjugation of quantum dot encapsulated in polystyrene colloids for cellular targeting

Soujanya Muralidhara1,2 Bridgette_Budhlall@uml.edu

Bridgette M Budhlall1,2 Bridgette_Budhlall@uml.edu

Krishnakumar M Malu3, Peter Gaines3. (1) Department of Plastics Engineering, University of Massachusetts, Lowell, MA 01854, United States (2) NSF Center for High-Rate Nanomanufacturing, University of Massachusetts, Lowell, MA 01854, United States (3) Department of Biological Sciences, University of Massachusetts, Lowell, MA 01854, United States

Novel bioimaging probes have been synthesized by the encapsulation of zinc sulfide coated cadmium selenide QD into PS colloids via a Pickering emulsion approach using laponite nanoclay as a stabilizer. Encapsulating QD within a polymer reduces the risk of toxic metal leakage without significantly its photoluminescence in vivo. The laponite are amenable to chemical modification. Functionalizing the laponite with primary amines opens up a wide range of possible bioconjugation reactions. The exceptionally high interaction between biotin and streptavidin was used to conjugate biomolecules to the PS-QD colloids. In order to facilitate biotinylation of the colloids, condensation between silanol groups on the laponite with aminopropyl triethoxysilane was first conducted and then Sulfo-NHS-Biotin was reacted to the amino group. Conjugated of these colloids with streptavidin-antibodies was then conducted to specifically target mitochondria in NIH3T3 cells. This protocol facilitated live imaging of mitochondria using confocal microscopy without the need to fix/stain the cells.

 

367. Effects of metal oxide nanoparticles on a model colon gut microbiome

Alicia A Taylor aliciaataylor@gmail.com

Ian M Marcus, Risa L Guysi, Sharon L Walker. Department of Chemical and Environmental Engineering, University of California, Riverside, Riverside, California 92521, United States

Nanoparticles are becoming more prevalent in consumer goods such as foods and cosmetics; hence, understanding the interactions between nanomaterials and bacteria in an engineered model colon can indicate the consequences of nanomaterial exposure on overall human health. Three nanoparticles were chosen at environmentally relevant exposure concentrations: TiO2 at 0.3mg per 100mL of liquid food, and CeO2 and ZnO both at a concentration of 0.1µg per 100mL of liquid food. Results indicate the nanoparticles cause a shift in the community's phenotype in three distinct phases: initial conditions, a transition period, and homeostasis, with the community exposed to the nanoparticles displaying significant differences in phenotypes such as hydrophobicity and electrophoretic mobility. The TiO2 nanoparticles have the longest phenotypic transition period, most likely due to its lack of dissociation and greater stability. The interplay between genotypic and phenotypic responses of the microbial community and the nanoparticle fate will be discussed.

 

368. Gauging colloidal and thermal stability in human IgG1 – sugar solutions through diffusivity measurements

Sven H Behrens1 sbehrens@gatech.edu

Jonathan Rubin1, Lars Linden2, Andreas S Bommarius1,3. (1) School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0100, United States (2) Global Biologics, Bayer Healthcare AG, Wuppertal, Germany (3) School of Chemistry & Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400, United States

Monoclonal antibodies are the fastest growing class of biotherapeutics. Ensuring their colloidal stability in liquid dispersions is crucial for maintaining therapeutic efficacy and economic viability. Sugars are often added to increase the colloidal and thermal stability of protein; yet, which type of sugar maximizes the stability benefits for a given protein is not known a priori, but usually determined by time and sample consuming stability tests. Here we show that the extent of stabilization by different sugars can be gauged by analyzing the proteins' diffusive virial coefficient kD. This protein interaction parameter is measured conveniently in a non-invasive, high-throughput manner using dynamic light scattering, and is found to correlate closely with experimental melting temperatures and dimerization rate constants for antibodies in different sugar solutions. The proposed analysis thus provides a rapid test of the subtle differences between inherently similar sugar-protein interactions; it should greatly facilitate the formulation of protein therapeutics.

 

369. Small angle neutron scattering studies of PLGA-PEG nanoparticle internal structure and its effects on in vitro drug release

Bin Yang by209@bath.ac.uk

John P Lowe, Karen J Edler. Department of Chemistry, University of Bath, Bath, Somerset BA2 7AY, United Kingdom

Understanding the internal structures within poly(lactide-co-glicolide)-block-poly(ethylene glycol) (PLGA-PEG) (PLGA-PEG) nanoparticles is fundamentally important to explain drug loading and drug release properties.1 Here, a PLGA-PEG copolymer was synthesized2 and used to prepare nanoparticles encapsulating carboplatin via different methods. The nanoparticles were characterized by DLS and zeta potential measurements. Small angle neutron scattering measurements and fitted models revealed that the PEG chains are not situated solely on the exterior surface of the particles, but form blocks of 12-20nm encapsulated inside PLGA nanoparticles, arranged in a fractal geometry. The calculated aggregation number of the PEG blocks is between 30-40 and the radius of gyration of the fractal aggregate is consistent with the particle size measured by DLS. Differences in the carboplatin loading and in-vitro release behavior will be discussed and compared to the measured internal structures. References (1) Dinarvand, R. Int J Nanomed 2011 , 6, 877. (2) Cheng, J. Biomaterials 2007 , 28, 869.

 

370. Electrowetting: mechanisms for the nano to the macroscale

Joelle Frechette jfrechette@jhu.edu

Mingxiang Luo, Rohini Gupta. Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD 21218, United States

We will discuss our efforts to understand the mechanisms behind electrowetting using condensation of a fluid in a nanopore.[1] We will also present other avenues for an applied potential to control wetting, such as using a voltage-induced conformational change. In the cases investigated we will pay special attention to contact angle hysteresis. In electrowetting on dielectric contact angle hysteresis is often considered a problem. Here we will discuss mechanisms in which a potential-dependent change in contact angle hysteresis can be employed to move drops on chemically homogeneous surfaces.[2] [1] Gupta, R.; Olivier, G. K.; Frechette, J., Invariance of the Solid-Liquid Interfacial Energy in Electrowetting Probed via Capillary Condensation. Langmuir 2010, 26 (14), 11946-11950. [2] Luo, M.; Gupta, R.; Frechette, J., Modulating Contact Angle Hysteresis To Direct Fluid Droplets along a Homogenous Surface. ACS Applied Materials & Interfaces 2012, 4 (2), 890-896.

 

371. Influence of proximal charged groups on interactions mediated by hydrophobic hydration

Derek Ma1 cdma@wisc.edu

Claribel Acevedo1, Samuel Gellman2, Nicholas Abbott1. (1) Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States (2) Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States

Water-mediated interactions involving hydrophobic domains are integral to colloidal and interfacial phenomena such as wetting and molecular self-assembly. Although it is now possible to experimentally test predictions involving homogeneous hydrophobic systems, hydrophobic domains are frequently in proximity to polar and charged groups. Theoretical studies predict that proximal hydrophilic groups can dramatically alter wetting and drying transitions involving hydrophobic domains, highlighting the need to understand hydrophobic interactions in heterogeneous systems. To address this knowledge gap, we used force spectroscopy to investigate interactions involving conformationally well-defined single oligomers of ß-amino acids (ß-peptides). The ß-peptides are designed to display nanoscopic chemical patterns of hydrophilic groups and hydrophobic domains. Our results provide experimental characterization of the influence of proximal cations on water-mediated interactions involving hydrophobic domains. The results also validate the use of ß-peptides in combination with force spectroscopy for understanding hydrophobic hydration in addition to wetting and drying transitions at nanoscopic length scales.

 

372. Carbon sequestration in deep saline aquifers: Interfacial tension and wettability of sc-CO2/brine/quartz systems

Soheil Saraji ssaraji@uwyo.edu

Lamia Goual, Mohammad Piri. Petroleum and Chemical Engineering, University of Wyoming, Laramie, Wyoming 82071, United States

Injection of CO2 in saline aquifers is considered as a method of carbon sequestration. The final storage capacity and the total amount of capillary-trapped CO2 during this process are affected by the interfacial tension (IFT) between fluids and the contact angle (CA) between fluids and mineral rocks. The interfacial properties of CO2/Brine/Mineral systems have been recently studied at low and moderate temperatures (T) and pressures (P), however very limited data exist at higher pressures and temperatures relevant to deep saline aquifers. In this study, the effects of pressure (2000-5000 psi), temperature (50-140°C), and brine salinities (0.1-5 M NaCl) on density, IFT, and dynamic CA of sc-CO2/brine/quartz systems are investigated in a systematic manner. The preliminary results indicate that IFT and CA are very sensitive to temperature, pressure, and brine salinity at elevated P and T.

 

373. Determining supported lipid bilayer phase transitions using a quartz crystal microbalance with dissipation monitoring

Andreas Wargenau wargenau@a-wargenau.de

Nathalie Tufenkji. Department of Chemical Engineering, McGill University, Montreal, QC H3A 2B2, Canada

Here, we report on a novel approach to measure the transition temperatures of supported lipid bilayers with the use of a Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D). We demonstrate that gel-liquid phase transitions can be detected by comparing the temperature-induced changes in the dissipation signal with corresponding data from the bare surface. Dissipative energy losses of a microbalance are sensitive to structural changes that occur within an adsorbed molecular film. In this study, the particular behavior observed for the lipid bilayers is not linked to the structural changes occurring during phase transition. It is rather believed that it originates in the accompanying heat transfer, which causes temporary alterations in the temperature of the adjacent medium, and hence, also in its viscosity. The advantage of our approach being independent of the structural membrane properties makes the QCM-D a promising tool for the detection of phase transitions in supported lipid bilayers.

 

374. Hygro-responsive membranes for energy-efficient separation of liquid mixtures

Gibum Kwon1 gbkwon@umich.edu

Arun K Kota1, Wonjae Choi2, Joseph M Mabry3, Anish Tuteja1. (1) Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109, United States (2) Department of Mechanical Engineering, University of Texas-Dallas, Richardson, TX 75080, United States (3) Space and Missile Propulsion Division, Air Force Research Laboratory, Edwards Air Force Base, CA 93524, United States

We have developed hygro-responsive (from the Greek prefix hygro meaning liquid) membranes that are counter-intuitively both superhydrophilic and superoleophobic. The developed membranes can separate a range of different immiscible liquid mixtures, including all types of oil-water mixtures, with greater than 99.9% separation efficiency using only gravity as the driving force. We also demonstrate the continuous separation of oil-water mixtures for over 100 hours without a decrease in flux. Our separation methodology uses only gravity and consequently is expected to be one of the most energy-efficient and cost-effective ways to separate oil-water mixtures. Further, we have developed a technique that combines liquid-liquid extraction and our fabricated membranes to separate numerous miscible liquid mixtures. We have utilized this technique for separating a wide variety of commercially relevant mixtures, including for the removal of sulfur from both gasoline and diesel to less than 1 part per million.

 

375. Accurate Measurement of Ultralow Interfacial Tensions of Aqueous Biphasic Systems

Ehsan Atefi1 ea32@zips.uakron.edu

Jay Adin Mann2, Hossein Tavana1. (1) Biomedical Engineering, The University of Akron, Akron, Ohio 44325, United States (2) Chemical Engineering, Case Western Reserve University, Cleveland, Ohio 44106, United States

Polymeric aqueous two-phase systems (ATPS) facilitate spatial patterning of living cells and biomolecules, confined in one aqueous phase, on substrates immersed in the second phase. The fidelity of patterns largely depends on the interfacial tension (IFT) of ATPS. Highly aqueous nature of both phases of ATPS results in extremely small IFT, making generation of accurate and reproducible data very difficult. We employ the axisymmetric drop shape analysis (ADSA) methodology, which is based on finding the best Laplacian curve fit to the extracted drop profile, to measure the IFT of a number of ATPS, both from sessile and pendant drops. We define specific criteria to eliminate the well-known problem of drop size and shape dependency of IFT. Our preliminary measurements show IFT values on the scale of 10 µJ/m2, i.e. three orders of magnitude smaller than that for oil-water systems. IFT systematically increase with polymer concentration of ATPS.