Symposium OrganizersHongyou Fan, Sandia National Laboratories
Donghai Wang, Pennsylvania State University
Earl Stromberg, Lockheed Martin Aeronautics
Ilhan Aksay, Princeton University
Symposium Support Oak Ridge National Laboratories
Sandia National Laboratories
CC2: Hierarchical Self-assembly and Nanostructures
Tuesday PM, April 10, 2012
Moscone West, Level 3, Room 3006
2:30 AM - CC2.1
Pressure-directed Folding and Unfolding Self-assembly of New Classes of Multi-dimensional Nanostructures
Hongyou Fan 1
1Sandia National Laboratories Albuquerque USAShow Abstract
Naturally occurred folding and unfolding systems such as self-assembled DNA bundles prove natural designs are hierarchical, with structures and property on multiple scales through interactions of subunits or building blocks. Mimicking these designs in fabrication of active materialsrequires a clear picture of energy landscaping that govern local interactions such as hydrogen bonding, van der Waals interactions, dipole-dipole interaction, capillary forces, etc, which will provide correct thermodynamic end points as well as facile kinetics for precise control of hierarchical structure for target function. To date, fabrications of active nanostructures have been conducted at ambient pressure and largely relied on these specific chemical or physical interactions. Here we show using Pressure-Directed Assembly (PDA) method we recently demonstrated, as an artificial tool, we can emulate natural folding and unfolding processes to explore energy landscaping that govern local interactions, to design new classes of active materials with structure and function that are not attainable for current materials, and to investigate new property resulted from the folding and unfolding processes. We show that under a hydrostatic pressure field, the unit cell dimension of a 3D ordered nanoparticle arrays can be manipulated to reversibly shrink and swell during compression and release of pressure, allowing precise tuning of interparticle symmetry and spacing, ideal for controlled investigation of distance-dependent energy couplings and collective chemical and physical property such as surface plasmon resonance. Moreover, beyond a threshold pressure, nanoparticles are forced to contact and sinter, forming new classes of chemically and mechanically stable 1-3D nanostructures that cannot be manufactured by current top-down or bottom-up methods. Depending on the orientation of the initial nanoparticle arrays, 1-3D ordered nanostructures (Au, Ag, CdSe, C60, etc) including nanorod, nanowire, nanosheet, and nanoporous network can be fabricated. Guided by computational simulations, we are able to rationalize the PDA of nanoparticle arrays for predictable nanostructures. PDA method mimics embossing and imprinting manufacturing processes and opens exciting new avenues for study folding and unfolding of active materials during compression (folding) and pressure release (unfolding). Exerting pressure-dependent control over the structure of nanoparticle or building block arrays provides a unique and robust system to understand collective chemical and physical characteristics. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energyâ?Ts National Nuclear Security Administration under contract DE-AC04-94AL85000.
3:00 AM - *CC2.2
Crafting Hierarchically Ordered Structures via Controlled Evaporative Self-assembly
Zhiqun Lin 1 Wei Han 1 Bo Li 1
1Georgia Institute of Technology Atlanta USAShow Abstract
Self-assembly of micro- and nano-scale materials to form ordered structures promises new opportunities for developing miniaturized electronic, optoelectronic, and magnetic devices. In this regard, several elegant methods based upon self-assembly have emerged, for example, self-directed self-assembly and electrostatic self-assembly. Dynamic self-assembly of nonvolatile solutes via irreversible solvent evaporation has been recognized as an extremely simple route to intriguing structures. However, these dissipative structures are often randomly organized without controlled regularity. In this presentation, we show a simple, one-step technique based on very simple â?ocoffee ringâ? phenomena to produce well-ordered structures (e.g., concentric rings, fingers, spokes, squares, triangular contour lines, ellipses, etc.) consisting of polymers or nanocrystals (NCs) with unprecedented regularity by allowing a drop of polymer or NC solution to evaporate in a curve-on-flat geometry. This technique, which dispenses with the need for lithography and external fields, is fast, cost-effective and robust. As such, it represents a powerful strategy for creating highly structured, multifunctional materials and devices.
3:30 AM - CC2.3
Surface Chemistry of Functional Nanoparticles for Self-assembling
Valerie Marchi Artzner 1 Franck Artzner 2 Marie Postic 2 Cyrille Hamon 1 Thomas Bizien 1 2 Pascale Even-Hernandez 1
1Universiteacute; Rennes 1 CNRS Chemistry Department UMR 6226 Rennes France2Institut de Physique de Rennes Rennes FranceShow Abstract
The inorganic nanoparticles possess a range of tunable optical fluorescence or absorption properties depending on their chemical composition and their shape (semi-conductor (QD) and metallic gold) whereas the surface ligand can be optimized to tailor interactions with the surroundings. Their properties can be used collectively within nanostructured materials. Nanoparticles (QD, Au) are also ideal building blocks for the construction of ordered 3D structures. We present here different strategies to solubilise, chemically-functionalize nanocrystals into water and to organize them in a controlled manner at a macroscale. The first one is based on the self-assembling properties of synthetic gallate amphiphiles (Boulmedais et al, Langmuir 2006 ; Roullier, V. et al Chem. Mat. 2008; Amela-Cortes et al. Chem. Comm. 2011) and the use of controlled water drying to self organize the nanoparticles. In the second approach, biological molecules and molecular self-assemblies are used as templates to organize well-defined inorganic nanostructures. The interaction between anionic peptidic quantum dots and cationic vesicles results in the formation of either hybrid QD vesicles or a well-defined lamellar hybrid condensed phase in which the QDs are densely packed in the plan of lamellas (Dif A. et al J. Am. Chem. Soc. 2008). The addition of the well-known anionic actin protein to this system induced the formation of fluorescent 3D crystalline fibers. We demonstrate the ability of a self-assembled 3D crystal template of helical actin protein filaments and lipids bilayers to generate a hierarchical self-assembly of quantum dots (Henry E; Dif A. et al submitted to Nanoletters 2011). Functionnalized tricystein peptidic Quantums Dots, QDs, are incorporated during the dynamical self-assembly of this actin /lipid template resulting in the formation of crystalline fibers. The crystal parameters, 26.5x18.9x35.5 nm3 are imposed by the membrane thickness, the diameter, and the pitch of the actin self-assembly. This process ensures the high quality of the crystal and results in unexpected fluorescence properties. This method of preparation offers opportunities to generate crystals with new symmetries and a larger range of distance parameters.
3:45 AM - CC2.4
Directed Assembly and In situ Manipulation of Semiconductor Quantum Dots in Liquid Crystal Matrices
Andrea Rodarte 1 Linda Hirst 1 Sayantani Ghosh 1
1UC Merced Merced USAShow Abstract
The ability to control and direct self-assembly of nanostructures into specific geometries with new functionalities, while preserving their original optical and electronic properties, is an attractive research endeavor. We have fabricated liquid crystal (LC) based matrices into which chemically synthesized nanostructures of varied morphologies and compositions are uniformly dispersed. Using high resolution spatially- and time-resolved scanning photoluminescence (PL) measurements, we demonstrate directed nanoparticle assembly and manipulation in situ . In our first experiment, we demonstrate both directional assembly and electric field modulated re-orientation of disk-shaped gallium selenide nanoparticles using a nematic LC matrix. A comparison of the photoluminescence (PL) spectra of isolated nanostructures and of those suspended in the nematic LC shows that the PL peak for the latter is red-shifted by 37 nm, indicating increased inter-particle coupling. Spatial scanning PL maps of nanostructure-LC composite samples reveal this coupling can be further enhanced by the application of an in-plane electric field along the director axis which causes the LC order parameter to increase. In addition to the effect of inducing increased order in the ensemble, using polarization resolved PL scans, we demonstrate re-orientation of the nano-assembly by the application of an in-plane E-field perpendicular to the original director axis. The LC mediated inter-dot coupling also affects the dynamical properties of the nanoparticles by increasing the excitonic recombination rate which is both direction and electric field dependent. In our second experiment, we demonstrate spectral and polarization modulation of chemically synthesized core shell CdSe/ZnS quantum dots (QDs) embedded in a one-dimensional photonic cavity formed by a cholesteric liquid crystal (CLC) matrix. A Cano-wedge cell varies the pitch of the CLC leading to the formation of Grandjean steps. This spatially tunes the photonic stop band, changing the resonance condition and continuously altering both the emission wavelength and polarization state of the QD ensemble. Contrary to expectations, we find that the emission is elliptically polarized and that the tilt of the ellipse, while dependent on the emission wavelength, additionally varies with distance across the Grandjean steps. Our work open up the possibility of designing new QD based optical devices where spatial control of orientation, wavelength and polarization of the embedded QDs would allow great flexibility and added functionalities. This work was funded by NSF, UC MERI and UC MEXUS.  Verma, et. al., Phys. Rev. B, 82, 165428 (2010).
4:30 AM - *CC2.5
Hierarchical Design of Polymer Composites for Self Healing Functionality
Jeffrey Moore 1
1University of Illinois Urbana USAShow Abstract
Damage-prone regions in structural composite materials are difficult to detect and even harder to repair. Damage is preceded by complex spatial and temporal changes in stress state, and it is therefore desirable to utilize these mechanical changes to activate â?" without human intervention â?" chemical changes that favorably alter materials properties when and where needed. Desirable properties brought about in response to damage or high-stress conditions include: (1) signal generation to warn of ensuing failure, (2) molecular structure modification to slow the rate of damage and extend lifetime (e.g., stress-induced crosslinking), and (3) repair of damage to avoid catastrophic failure (e.g., crack-filling and interface rebonding). To achieve these properties, composites must be designed to respond to changes at various length scales. At the atomistic level, chemical bond changes and conformational changes occur. On a supramolecular level, chain slippage occurs as a response to force and deformation. At the microscopic level, voids, cavitation, yield or crazing, and crack formation take place along with large scale viscoelastic deformation. This talk will describe molecular to macroscopic approaches to achieve self-healing functionality in polymer composites.
5:00 AM - *CC2.6
Induction of Cellular Responses by Nanoscopic Environments
Joachim P Spatz 1
1Max Planck Institute for Intelligent Systems amp; University of Heidelberg Stuttgart GermanyShow Abstract
Our approach to engineer cellular environments is based on self-organizing spatial positioning of single signaling molecules attached to inorganic or polymeric supports, which offers the highest spatial resolution with respect to the position of single signaling molecules. This approach allows tuning cellular material with respect to its most relevant properties, i.e., viscoelasticity, peptide composition, nanotopography and spatial nanopatterning of signaling molecule. Such materials are defined as â?onano-digital materialsâ? since they enable the counting of individual signaling molecules, separated by a biologically inert background. Within these materials, the regulation of cellular responses is based on a biologically inert background which does not trigger any cell activation, which is then patterned with specific signaling molecules such as peptide ligands in well defined nanoscopic geometries. This approach is very powerful, since it enables the testing of cellular responses to individual, specific signaling molecules and their spatial ordering. Detailed consideration is also given to the fact that protein clusters such as those found at focal adhesion sites represent, to a large extent, hierarchically-organized cooperativity among various proteins. Moreover, â?onano-digital supportsâ? such as those described herein are clearly capable of involvement in such dynamic cellular processes as protein ordering at the cellâ?Ts periphery which in turn leads to programming cell responses.
5:30 AM - CC2.7
Nano- Meets Micro-: Programmed Assembly of Biological Building Blocks on Microfabricated Electrodes
Roberto de la Rica 1 Ernest Mendoza 2 Molly M Stevens 1
1Imperial College London London United Kingdom2Centre de Recerca en Nanoenginyeria, Universitat Politecnica de Catalunya Barcelona SpainShow Abstract
The fabrication of structures with nanometric resolution is of great importance for the manufacture of next generation circuits, sensors and solar cells. [1,2] However, the top-down production of nanostructured materials often requires sophisticated equipment and takes place in specialized facilities, which increases the costs associated with the manufacturing process. By contrast, in biological systems the self-assembly of nanometric building blocks to yield micrometric and millimetric structures with a high order of hierarchical organization is a ubiquitous phenomenon that happens in mild conditions. Yet, it is difficult to control these self-assembly processes ex vivo to yield structures of controlled size and shape for their integration with standard technologies. For example, it is well known that collagen self-assembles to yield a plethora of structures with different dimensions and degree of hierarchical organization. However, it is difficult to harness this self-assembly process to obtain a single population of assemblies with a particular set of desirable features. To advance the current state of the art we have programmed the bottom-up assembly of biological building blocks to yield micrometric structures of controlled dimensions that bridge a pair of microfabricated electrodes. The key step of this methodology is to use alternating currents to concentrate and align collagen precursors to trigger their self-assembly at the gap between the electrodes so that hierarchically organized structures are obtained that are straightforwardly integrated with the circuit. By fine tuning the relevant parameters of the fabrication process it is possible to control the orientation and organization of the building blocks in the assemblies as well as the size of the resulting biomolecule collectives. The collagen bridges, fully integrated with the chip, can be used as templates for the growth of semiconducting materials as well as for the design of ultrasensitive sensors.  de la Rica, R.; Fabijanic. K. I.; Baldi, A.; Matsui, H. Angew. Chem. Int. Ed. 2010, 49, 1447-1450.  Aili, D.; Stevens, M. M. Chem. Soc. Rev. 2010, 39, 3358-3370.  de la Rica, R.; Velders, A. H. J. Am. Chem. Soc. 2011, 133, 2875-2877.  de la Rica Roberto; Mendoza Ernest; Lechuga Laura M.; Matsui, H. Angew. Chem. Int. Ed. 2008, 47, 9752-9755.
CC3: Poster Session: Hierarchical Nanostructure I
Tuesday PM, April 10, 2012
Moscone West, Level 1, Exhibit Hall
6:00 AM - CC3.1
Self-alignment of Petal-like Hierarchical Iron Oxide Particles in Magnetorheological Fluid
Youngsoo Jung 1 You-Hwan Son 1 Jung-Kun Lee 1
1University of Pittsburgh Pittsburgh USAShow Abstract
Nanostructured magnetic materials have attracted considerable attentions because of their novel potentials in biological and engineering applications. One of their interesting properties is that the magnetic nanoparticles in solutions can be aligned when an external magnetic field is applied. Such solutions containing magnetic materials, so called magnetorheological (MR) fluids or ferrofluids, are regarded as one of the smart materials. In magnetorheological fluids, important phenomena are inter-particle interaction and material adsorption that occur on the surface of the magnetic particles. Therefore, the surface morphology of the magnetic particles is one of the most important aspects that determine the functionalities of magnetic particles in magnetorheological fluids. To date, however, the spherical magnetic nanoparticle such as carbonyl iron (CI), magnetite (Fe3O4), maghamite (Î³-Fe2O3) particles or beads containing magnetic multicores with different surface layer have been mainly used as a stimuli-responsive materials under magnetic field. In this presentation, we report the magnetorheological behavior of nonspherical particles that have hierarchical structure and large surface area with an emphasis on the effect of the surface morphology on the viscoelastic properties of fluids under magnetic field. The fluids consisting of self-assembled iron oxide particles exhibit highly tunable viscoelasticity which is controlled by applying external magnetic field. The storage modulus of the hierarchical particle fluids is 2 times as large as that of the spherical particle fluid. A difference between hierarchical particles and spherical nanoparticles is explained by the fact that surface features of the hierarchical particles facilitate the self-alignment and increased the network strength between particles in the fluids. Compared with the smooth surface of the spherical particles, the rugged surface of the self-assembled particles fits well each other, which increases a resistance to the free motion of magnetic particles that are aligned by magnetic field.
6:00 AM - CC3.11
Micelles of pi;-containing Small-molecule Hydrophobic Amphiphiles: A New Concept in Solution Assembly
Martin James Hollamby 1 Takashi Nakanishi 1
1National Institute for Materials Science Tsukuba JapanShow Abstract
We present a new concept in solution assembly: the non-polar solvent-driven micellization of a fully hydrophobic small molecule. Surfactants and amphiphilic polymers are known to form a variety of solution assembly states. However, for these conventional amphiphiles, the hydrophobic and hydrophilic parts differ greatly, with very different intermolecular interactions, which help drive assembly. Here, the following question is addressed: â?oIs it possible to generate micelles in solution using a small molecule using only van der Waals forces or Ï?-Ï? interactions?â? While recognizable micellization has been noted for hydrophobic long-chain di-block co-polymers (e.g. poly(styrene-b-isoprene), (e.g. Soft Matter 2009, 5, 1081) it was not observed until now in smaller, surfactant-like species. The chosen candidate was a C60-containing molecule that has previously been noted to form functional self-organized structures out of solution (e.g. Chem. Commun. 2010, 46, 3425). This hydrophobic amphiphile was observed to micellize in solution, with the extent of micellization strongly solvent-dependent. Small-angle scattering using x-rays (SAXS at SPring 8, Japan and an in-house beam-line, NIMS) and neutrons (SANS at SANS2D, ISIS, UK and D11, ILL, France) was used to build up a detailed picture of the micelle structure. In this presentation, we will discuss the control of micelle size and shape using solution parameters, with the aim to use this novel paradigm to generate functional systems.
6:00 AM - CC3.12
Hierarchical Transformation of Ag Morphologies on Clay Film Surface
Karlene Liang 1 Ya-Chi Wang 1 Jiang-Jen Lin 1
1Polymer Science and Engineering Taipei TaiwanShow Abstract
The silver nanoparticles-clay thin films were fabricated by in situ reduction of silver nitrate in the presence of nanoscale silicate clays and subsequent water evaporation on glass. Upon the controlled thermal treatments, the generated Ag nanoparticles (AgNP) were observed to have high mobility into the film surface and further self-aggregation to form unique morphologies such as cube-, rod- and wire-like nano- to micro-meter sizes. The hierarchical transformation of these AgNP morphologies is largely influenced by the presence of nanoscale silicate platelets (NSP) that are previously synthesized by the exfoliation process of the natural clay stacks. The heating conditions and kinetic observation of the nanoparticle formation and morphological changes were investigated. The hybrids of AgNP/NSP) were prepared by annealing the film precursors at different temperatures (80, 150 and 200 oC) over a period of hours. It was observed by scanning electronic microscope for the kinetic migration of small AgNP between the clay layers and diffusion into the clay surface. On the surface, the AgNP further coalesced into hierarchical size and shape changes. The annealing conditions may affect the migration and morphology of the Ag particles for various compositions of AgNP/NSP at 1/9, 3/7 and 5/5 weight ratios. For example, a dynamic mobility of Ag to form hierarchical changes from spherical (diameter ~ 50 nm), to cubic (length ~100 nm), and then to rod-like shapes (length ~ 1.6 Î¼m and width ~300 nm). The thin clay film at 1.0 nm thickness may affect the dimensional growth of Ag particles in different directions, hence controlling the formation of various shapes such as spherical nanoparticles, cubes or further growing into lengthy rods. The manipulation of Ag particle morphologies and migration behaviors can be used for the fabrication of new Ag crystals for conductors and other applications.
6:00 AM - CC3.13
Simple Fabrication of Asymmetric Polymer Nanostructures by Reusable AAO Templates
Bong Seock Kim 1 Nayoung Hong 1 Moon Kee Choi 1 Su Yang Lee 2 Il Won Kim 2 Kyusoon Shin 1
1Seoul National University Seoul Republic of Korea2Soongsil University Seoul Republic of KoreaShow Abstract
1D nanomaterials such as high-aspect-ratio polymer nanopillars have received great attention as asymmetric structure because of their wide potential applications including Gecko-mimicking dry adhesives, microfluidics, water delivery, unidirectional wetting, nanotemplate, piezoelectric nanogenerators and micro-mechanical sensors. However, making nanoscopic structures with asymmetry is still a fascinating issue as both academic and industrial points of view. In most studies, nanopillars were fabricated by photolithography, e-beam lithography or soft lithography. But these techniques have the inherent limitation of manufacturing because of high cost, low throughput and the difficulty of making high-aspect-ratio. In recent years, anodized aluminum oxide (AAO) has become a challenging template system to overcome these limitations. Based on the self-assembly mechanism of the nanopore formation, AAO has uniform and hexagonally packed highly ordered nanoscopic pores with high-aspect-ratio. In addition, the diameter and length of AAO nanopores is easy to control by well established conditions. The general method to obtain high-aspect-ratio nanopillars from AAO includes the infiltration of polymeric materials into the nanopores and the dissolution of the AAO master template. In this method, removing master template restricts the recycling of the master mold. As a solution to this inefficiency, UV-curable polymers for mold casting might be applied. However, releasing the nanopillars from the mold is still difficult during the fabrication of high-aspect-ratio nanopillars because the difference of the surface energy between AAO and the polymer is small. In reference to these issues, we present a simple method of utilizing AAO as a reusable template for fabricating high-aspect-ratio polymeric nanopillars. Furthermore, our experiments include the method of manufacturing the bended or deformed structure of nanopillars to obtain more asymmetricity because 1D nanopillars still have the symmetric conformation based on the perpendicular plane against pillar axis.
6:00 AM - CC3.16
Electric Field Driven Self-assembly of Close-packed Monolayers of Gold Nanoparticles Suspended in a Nonpolar Solvent
Samuel David Oberdick 1 Sara Majetich 1
1Carnegie Mellon University Pittsburgh USAShow Abstract
We investigate electric field driven self-assembly of monolayers of charged gold nanoparticles suspended in a nonpolar solvent, hexane. Giersig and Mulvaney have reported electric field driven self-assembly of monolayers of gold nanoparticles (~20 nm) dispersed in water, as opposed to a nonpolar solvent (1). However, this mechanism for self-assembly has remained controversial, since evaporation and drying of colloidal nanoparticle solutions can also produce monolayers. Our nanoparticles are synthesized using the method of Martin et. al. (2). They are ~5 nm in diameter and stabilized with dodecanethiol. Electrophoretic mobility measurements indicated that the nanoparticles have a charge of â?"e or -2 e. These nanoparticles are injected into a parallel plate electrophoretic cell. One of the electrodes was a piece of copper with a surface area of 5.25 cm^2. The second electrode was a 3 mm carbon-coated copper TEM grid. The spacing between the electrodes was 0.3 cm. The nanoparticles were deposited on the TEM grid for imaging. Both the voltage and the exposure time were varied. The amount of deposited particles increased monotonically with an increase in voltage or time over which the voltage is applied. This indicates that particle deposition is not due to evaporative effects, but is driven by the electric field. For high voltages (20 V) and long depositions times (15 â?" 30 min), we observed large islands of close packed monolayers with dimensions up to a few microns. Within these monolayers, the nanoparticles self assemble due to a combination of the electric field, the steric barriers between particles, and van der Waals forces. This technique has potential for nanoparticle self-assembly on patterned substrates since the self-assembly is a parallel, rather than serial, process. (1) Giersig, M.; Mulvaney, P. Langmuir 9 (1993) 3408. (2) Martin, M. N.; Basham, J. I.; Chando, P.; Eah, S.-K. Langmuir 26 (2010) 7410.
6:00 AM - CC3.17
New Chemical Methods for Selective Nano-scale Functionalization
Tina Gschneidtner 1 Kasper Moth-Poulsen 1
1Chalmers Gothenburg SwedenShow Abstract
Selective functionalization of nanostructures with nanometer resolution is important for the development of a broad range of applications ranging from single molecule electronics to advanced sensor technologies where the single molecule is used as the sensing unit. Today nano-scale functionalization is typically achieved using a combination of top-down lithographic techniques and chemical self-assembly. The resolution is therefore limited to the resolution of the lithographic technique- typically in the 30-100 nm range. Improved resolution and selectivity is highly desirable since it might lead to new opportunities in a broad range of applications ranging from single molecular electronics to sensor and nano-medicine. Hierarchical self-assembly would be an elegant way to fabricate multiple single molecule devices in a parallel way using chemical self-fabrication and photo-induced functionalization methods. Jain et al.1 have recently shown that the build-up of gold nanorod dimers with one molecule in between is possible and therefore it is a suitable approach towards the challenge of contacting single molecules by macroscopic wires. No pre-fabricated nanogap via lithography is necessary, since the nanogap is built up by the chemical synthesis and self-assembly of gold nanoparticles with the support of the molecule. By synthesizing new molecular bridges with functional chemical groups we hope to be able to use this approach to construct nanorod dimers attached to a single active functional molecule. Further functionalization of self-assembled molecules can be achieved selectively by highly efficient photocleavable protecting groups.2 Light directed synthesis on a photoactive SAM can provide micropatterns that can be used for array-based screening, solid-supported peptide synthesis, sensor and diagnostic applications. 1 Jain, T., Westerlund, F., Johnson, E., Moth-Poulsen, K. and BjÃ¸rnholm, T. ACS Nano, 2009, 3828-834. 2 Moth-Poulsen, K., Kofod-Hansen, V., Kamounah, F. S., Hatzakis, N. S., Stamou, D., Schaumburg, K. Christensen, J. B. Bioconjugate Chem., 2010, 21, 1056-1061.
6:00 AM - CC3.18
Ultra-Large-Area Nanoparticle Monolayers by Controlled Solvent Evaporation
Tianlong Wen 1 Sara A Majetich 1
1Carnegie Mellon University Pittsburgh USAShow Abstract
Large area self-assembled monolayers of surfactant coated nanoparticles were fabricated on an aqueous subphase by controlling the evaporation of the colloidal solution carrier fluid.1 In this technique, nanoparticles were dispersed in a binary solvent mixture of toluene and hexane. The difference in solvent volatility and partial coverage of the trough leads to a flux of nanoparticles toward the evaporation front. The mass transport of nanoparticles continuously feeds the growth of monolayers to yield large area continuous monolayers. This technique has been used to successfully make monolayers comprised of oleic acid coated magnetite and manganese oxide nanoparticles, and alkane thiol coated gold nanoparticles.Monolayer formation is affected by the mixing ratio of hexane and toluene, the concentration of surfactant and the size distribution of the nanoparticles. The floating monolayers are transferred onto different substrates by the Langmuir-Schaefer method. Monolayer transfer is dependent on the interaction between the monolayer and the substrate, which is determined by surfactants in the monolayer and substrate materials. Nanoparticle bilayers were obtained by double deposition. These arrays had registry between the layers, with a number of different twist angles. This technique can be used to prepare large-area self-assembled nanoparticle monolayers. . T. Wen and S. A. Majetich, Ultra-large-area self-assembled monolayers of nanoparticles, ACS Nano, Article ASAP (2011), DOI: 10.1021/nn2037048
6:00 AM - CC3.19
A Platform for Characterizing Cell Membrane Mimics: Lipid Bilayer Membranes on Graphene and Gold Surfaces
Xi Wang 1 Gouri Radhakrishnan 2 Regina Ragan 1
1University of California-Irvine Irvine USA2The Aerospace Corporation Los Angeles USAShow Abstract
Lipid bilayer membranes (LBMs) as cell membrane mimics assembled on a solid electrode are an attractive platform for sensing protein-membrane or protein-protein interactions. In this work, LBMs were assembled on two conducting substrates â?" graphene and gold (Au). Graphene is a transparent and highly conductive electrode with biological compatibility. Graphene was grown on copper (Cu) by chemical vapor deposition by employing methanol as the precursor and pure Argon as the process/carrier gas without any added hydrogen. In the case of Au, the template stripping (TS) method was used to obtain atomically flat and pristine Au surfaces. This method has promise for large-scale tethered (t)LBM array manufacturing for high-throughput drug screening. 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) vesicles were deposited on graphene and Au surfaces and LBM formation and vesicle fusion dynamics were monitored using atomic force microscopy (AFM) topography imaging and force spectroscopy in a fluid cell under buffer conditions at room temperature. AFM topography images show sLBMs form on graphene with tubular features having relative orientation of 120 degree on Cu foils, while a uniform sLBM formed on graphene deposited on Cu single crystal. Interestingly, when POPC vesicles were deposited on highly ordered pyrolytic graphite (HOPG) surface, multilayers of LBMs form where the first layer of LBM is continuous, and the second layer exhibits tubular features with an orientation angle coincident with the step edge orientation of HOPG. These results suggest that the step edge of Cu below graphene may also guide the assembly of tubular LBM features. In order to assemble tLBMs on TS Au, POPC vesicles were functionalized with 2.5 mol% 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-poly(ethylene glycol)-2000-N-[3-(2-pyridyldithio)propionate] (DSPE-PEG-PDP), since POPC vesicle fusion does not spontaneously occur on unfunctionalized Au surfaces. Critical forces for vesicle rupture as a function of DSPE-PEG-PDP molar concentration in POPC vesicles on TS Au were examined using AFM force spectroscopy. The critical force needed to initiate tLBM of 2.5 mol% DSPE-PEG-PDP/97.5 mol% POPC formation is approximately 1.1 nN and that for 10 mol% DSPE-PEG-PDP/90 mol% POPC was approximately 0.5 nN. The lower critical force needed for tLBM formation with higher concentration of DSPE-PEG-PDP suggests that Au-thiolate bonding between DSPE-PEG-PDP and TS Au increases vesicle-substrate interactions promoting vesicle fusion. In contrast, higher forces applied during AFM tapping mode scanning of pure POPC vesicles on TS Au did not lead to observable LBM formation. Adsorbed vesicles remain on the surface, indicating that DSPE-PEG-PDP tethering molecules are needed to promote vesicle fusion on TS Au. These results show that both systems, LBM on graphene or on Au can be developed into a versatile platform for biosensing and drug-screening applications.
6:00 AM - CC3.2
Syntheses of Nanostructured Cu- and Ni-based Micro-assemblies with Selectable 3-D Hierarchical Biogenic Morphologies
Yunnan Fang 1 John D Berrigan 1 Ye Cai 1 Seth R Marder 2 1 Ken H Sandhage 1 2
1Georgia Institute of Technology Atlanta USA2Georgia Institute of Technology Atlanta USAShow Abstract
A combined layer-by-layer (LbL) surface amine amplification and electroless deposition process has been developed, for the first time, to convert biologically-replicable three-dimensional (3-D) nanostructured micro-assemblies (such as siliceous diatom frustules and beetle scales) into freestanding Cu-bearing or Ni-bearing structures that retain the starting biogenic microscale 3-D shapes and nanoscale patterns. After reacting the hydroxyl-bearing surfaces of these biotemplates with an aminosilane to introduce surface amine groups, an LbL polyacrylate/polyamine deposition process was used to dendritically amplify the surface amine concentration. Subsequent binding of metal chloride catalysts to these amine-enriched surfaces enabled the rapid electroless deposition of thin, conformal, continuous, and nanocrystalline or amorphous metallic coatings on the 3-D biotemplates. Selective removal of the underlying templates then yielded freestanding Cu-bearing or Ni-bearing structures. The conformality and continuity of the thin coatings, and the fidelity with which the biogenic shape and fine features were preserved in the freestanding structures, were significantly enhanced by the amplification of surface amines (and the associated enrichment of catalytic sites) resulting from the LbL polyacrylate/polyamine treatment. Monolithic and multicomponent structures (e.g., Cu, multilayer Au/Cu, CuO, and Ni-P alloy) with bio-derived morphologies have been synthesized utilizing this approach. This readily-scalable process may generally be used to convert self-assembled rigid templates (of biological or synthetic origin) into nanostructured transition metal- and noble metal-based microassemblies with a wide variety of selectable 3-D hierarchical morphologies for use in numerous functional and structural applications.
6:00 AM - CC3.21
Pressure-directed Folding and Unfolding Self-assembly of New Classes of Multi-dimensional Nanostructures
Binsong Li 1 Huimeng Wu 1 Jianyu Huang 1 Wenbin Li 2 Ju Li 2 Hongyou Fan 1 3
1Sandia National Laboratories Albuquerque USA2Massachusetts Institute of Technology Cambridge USA3NSF/University of New Mexico, Center for Micro-Engineered Materials Albuquerque USAShow Abstract
Naturally occurred folding and unfolding systems such as self-assembled DNA bundles prove natural designs are hierarchical, with structures and property on multiple scales through interactions of subunits or building blocks. Mimicking these designs in fabrication of active materials requires a clear picture of energy landscaping that govern local interactions such as hydrogen bonding, van der Waals interactions, dipole-dipole interaction, capillary forces, etc, which will provide correct thermodynamic end points as well as facile kinetics for precise control of hierarchical structure for target function. To date, fabrications of active nanostructures have been conducted at ambient pressure and largely relied on these specific chemical or physical interactions. Here we show using Pressure-Directed Assembly (PDA) method we recently demonstrated, as an artificial tool, we can emulate natural folding and unfolding processes to explore energy landscaping that govern local interactions, to design new classes of active materials with structure and function that are not attainable for current materials, and to investigate new property resulted from the folding and unfolding processes. We show that under a hydrostatic pressure field, the unit cell dimension of a 3D ordered nanoparticle arrays can be manipulated to reversibly shrink and swell during compression and release of pressure, allowing precise tuning of interparticle symmetry and spacing, ideal for controlled investigation of distance-dependent energy couplings and collective chemical and physical property such as surface plasmon resonance. Moreover, beyond a threshold pressure, nanoparticles are forced to contact and sinter, forming new classes of chemically and mechanically stable 1-3D nanostructures that cannot be manufactured by current top-down or bottom-up methods. Depending on the orientation of the initial nanoparticle arrays, 1-3D ordered nanostructures (Au, Ag, CdSe, C60, etc) including nanorod, nanowire, nanosheet, and nanoporous network can be fabricated. Guided by computational simulations, we are able to rationalize the PDA of nanoparticle arrays for predictable nanostructures. PDA method mimics embossing and imprinting manufacturing processes and opens exciting new avenues for study folding and unfolding of active materials during compression (folding) and pressure release (unfolding). Exerting pressure-dependent control over the structure of nanoparticle or building block arrays provides a unique and robust system to understand collective chemical and physical characteristics. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energyâ?Ts National Nuclear Security Administration under contract DE-AC04-94AL85000.
6:00 AM - CC3.23
Stress-induced Bimodal Ordering in POSS/PCL Biodegradable Shape Memory Nanocomposites
Bonifacio Alvarado-Tenorio 1 Angel Romo-Uribe 1 Patrick T Mather 2
1Universidad Nac A de Mexico Cuernavaca Mexico2Syracuse University Syracuse USAShow Abstract
Simultaneous wide- and small- angle X-ray scattering (WAXS-SAXS) has revealed a stress-induced bimodal orientation of POSS crystals and PCL chains, both in a constrained POSS/PCL crosslinked network architecture with shape memory properties. POSS/PCL nanocomposites with molecular weight of 2,600 g/mol exhibiting shape memory behavior were synthesized and variation of crosslinker molar ratio was used to obtain POSS/PCL networks with different crosslink density (Alvarado-Tenorio et al., Macromolecules, 44, 5682, 2011). In that study it was shown that there are POSS crystals embedded in an amorphous PCL matrix, and the POSS crystals were ordered in a cubic nanostructure. In this work, it will be shown that elongation at room temperature of all the networks yielded a double-induced orientation (90 and 180 degrees) of the POSS crystals, as indicated by the 101 reflection. Moreover, it was also detected stretched-induced crystallization of the otherwise amorphous PCL chains. Furthermore, SAXS data showed long periods in the meridional and equatorial orientations of 630, 90 and 45 Angstroms corresponding to a lamellar nanostructure of PCL chains. The induced bimodal orientation of the POSS-PCL molecular network will be correlated with its shape memory properties.
6:00 AM - CC3.24
Elastic Conductors with Extreme Nanoparticle Content
Yoonseob Kim 1 Matthew D Prima 1 Jian Zhu 1 Xianli Su 2 Bongjun Yeom 1 Ctirad Uher 2 Nicholas A Kotov 1
1University of Michigan, Ann Arbor Ann Arbor USA2University of Michigan, Ann Arbor Ann Arbor USAShow Abstract
Driven by potential applications such as bioelectronics, wearable electronic devices, and robotics; the field of elastic conductors acquired renewed importance. In the last decade, tremendous research and development efforts have been invested in exploring the functionalities envisioned for carbon nanotubes (CNTs) with various elastic substrates. The adoption of CNTs was primarily driven by its high aspect ratio that resulted in composites with high conductivity during stretching. Common elastic conductors from CNTs, however, have several problems; such as high quality of composite is not often reproducible, higher conductivity is unlikely, and properties are anisotropic. In order to improve the current design of elastic conductors, we need to design nanocomposite materials that have superior properties and functionalities than current materials. To satisfy this requirement, we present elastic conductors from extreme content of nanoparticles (NPs) with polymer matrix by layer-by-layer (LBL) assembly technique and a method of filtration. Nanocomposites from LBL assembly have superior electromechanical properties as well as chemical stability. From a classical chemical standpoint that a dispersion of NPs can be easily aggregated by polymer solution of a different charge was expected and the aggregate was obtained by filtration to yield films. It is thus an intriguing engineering question to compare properties of nanocomposites by two methods. NPs, in general, might be an inadequate choice as fillers because they do not have as high aspect ratio as CNTs, however specially synthesized NPs with judiciously chosen polymer matrix are expected to have superior electromechanical properties and dynamics of the composite and these are rarely studied. It is therefore important to understand the basics of the charge transport in our composites containing such a high content of NPs, which obviously make them quite superior to traditional composites. Overall, successful outcome of this research project will be a significant step forward in terms of both exceptional properties and unique material design.
6:00 AM - CC3.25
High Performance Self-assembly for Advanced Plastic Electronics
Kyung M. Choi 1
1University of California Irvine USAShow Abstract
Silicon compounds have been widely used then extended to nanotechnology area. We introduce a use of silicon elastomer attached with a photocurable self-assembly group as stamp materials in soft lithography. 'Soft lithography' is an alternative technology of conventional UV photolithography, which has attracted much attention in â?~pattern transferâ?T and â?~microfabricationâ?T by making stamps, molding, and contact-printing processes due to its low-cost and easy processability, for use, particularly in plastic/molecular electronics. The resolution of soft lithography technique relies on the elastomeric elements. Since commercially available silicon elastomers often results in collapse and mergence due to their low mechanical strength, especially in the nano-scale regime(<100 nm), these limitations have motivated us to develop a new stiff, photocured silicon elastomers, with a photocurable self-assembly functionality. Using the designed silicon rubber materials, we demonstrated its unique capability for the case of nano-striated features of 300 nm width and 600 nm height in photoresist, which is one of the most challenging â?~nano-patterning tasksâ?T in advanced soft lithography. We also demonstrated â?~elastomeric photopatternsâ?T in the ~5 micrometer resolution range using a new photocurable, stiff silicon rubber prepolymer.
6:00 AM - CC3.27
Decoration of Flexible Metal-organic Coordination Networks by Reactive Ni Atoms at Surfaces
Jan Cechal 1 Christopher S Kley 1 Takashi Kumagai 1 Frank Schramm 2 Mario Ruben 2 3 Sebastian Stepanow 1 Klaus Kern 1 4
1MPI-FKF Stuttgart Germany2KIT Karlsruhe Germany3Strasbourg University Strasbourg France4EPFL Lausanne SwitzerlandShow Abstract
A highly flexible and adaptable two-dimensional metal-organic coordination network (MOCN) is synthesized from rod-like 4,4'-di-(1,4-buta-1,3-diynyl)-benzoic acid (BDBA) and Fe atoms on Au(111) and Ag(100) surfaces and studied by scanning tunneling microscopy under ultra-high vacuum. The network grows continuously over multiple surface terraces through mutual in-phase structure adaption of network domains on terraces and at step edges. The adaptability of the MOCN to intrinsic surface defects is mainly ascribed to the high degree of conformational flexibility of the butadiyne backbone of the ligand. Furthermore, the selective interaction of transition metal atoms with distinct functional groups of the ligand molecule enables the fabrication of surface confined MOCN decorated by atoms of the second metal. Since Fe forms strong coordination bonds with the carboxylate groups and Ni shows a high affinity to the butadyine backbone, the Fe-BDBA coordination network provides a robust host for Ni atoms that is thermodynamically stable even at temperatures above 380 K. It is found that the substrate plays a significant role in the incorporation of Ni atoms in the organic matrix. On Au(111) only the decoration of phenyl rings was observed whereas on Ag(100) the Ni is located near the butadiyne backbone presumably embedded in the first substrate layer. The incorporated Ni atoms can be utilized for the catalytic conversion of gas molecules, and serve as stable nucleation centers for metal clusters as well as for the selective binding of further ligands into the network cavities. The presented results open the way for the designed hierarchical assembly of complex functional structures at surfaces.
6:00 AM - CC3.29
Assembly of Metal Oxide Nanoparticles through Coordination Bond
Seiichi Takami 1 Takanari Togashi 1 Shunsuke Asahina 2 Tadafumi Adschiri 1 Osamu Terasaki 3 4
1Tohoku Univ. Sendai Japan2JEOL (EUROPE) SAS Croissy-sur-Seine France3KAIST Daejeon Republic of Korea4Stockholm Univ. Stockholm SwedenShow Abstract
We have studied the synthesis of organic-modified metal oxide nanocrystals [1-3] by simply performing hydrothermal synthesis in the presence of organic molecules. The organic molecules that were tethered on the nanocrystals controlled the surface chemical character and enabled better handing of nanocrystals including the longer colloidal stability, reduced viscosity of concentrated dispersion, and the mixing with polymers at higher concentration. In addition to these merits, we believe that the surface modification of metal oxide nanocrystals provides novel strategies to realize new functions and properties of metal oxides. We found that the organic molecules on the surface of metal oxide nanocrystals enabled their ordered assembly. In this presentation, we report the self-assembly of metal oxide nanoparticles through coordination functional groups that are displayed on the surface, focusing on cubic assembly of octahedral primary CeO2 nanoparticles [4,5] and superparamagnetic behavior of the assembly of Fe3O4 nanoparticles with the size of up to ~500 nm.  This result might lead to the assembly of several kinds of nanocrystals to realize the hybridization of various functions of metal oxides.  S. Takami, et al., Mater. Lett. 61, 4769, 2007.  M. Taguchi, et al., Cryst. Growth Des. 9, 5297, 2009.  M. Taguchi, et al., CrystEngComm 13, 2841, 2011.  S. Takami, et al., Dalton Trans., 5442, 2008.  S. Asahina, et al., ChemCatChem 3, 1038, 2011.  T. Togashi, et al., Dalton Trans. 40, 1073, 2011.
6:00 AM - CC3.3
Hierarchically Self-assembled 3D Layered Double Hydroxide/Carbon Nanotube Nanoarchitectures
Meng-Qiang Zhao 1 Qiang Zhang 1 Jia-Qi Huang 1 Gui-Li Tian 1 Fei Wei 1
1Tsinghua University Beijing ChinaShow Abstract
Well arrangement and construction of different low-dimensional nanomaterials (e.g. zero-dimensional (0D) nanoparticles (NPs), one-dimensional (1D) nanotubes, nanowires, nanorods, and two-dimensional (2D) flakes) as building blocks with two or more levels from the nanometer to the macroscopic scale leads to the formation of three-dimensional (3D) hierarchical nanocomposites with unique properties. Here, we reported the self-assembly of a family of 3D hierarchical nanocomposites of carbon nanotubes (CNTs) and layered double hydroxides (LDHs) by direct chemical vapor deposition. Co-precipitation was firstly involved to synthesize LDHs from metal cations and interlayer anions. CNTs were assembled into the composite by chemical vapor deposition (CVD) of carbon sources, such as methane and ethylene. A hierarchical nanocomposite with the structure of single/double walled CNTs interlinked with two-dimensional flakes is constructed via in situ CNT growth onto LDH flakes . Both wall number and diameter of the CNTs and composition of the flakes can be easily tuned by changing the proportion of transition metal in LDH flakes. Furthermore, continuously interlinked CNT layer alternating with lamellar flakes structure is obtained after the compression. The hierarchical composite is demonstrated to be excellent filler for strong polyimide film. This kind of hierarchical nanocomposite can also be mass produced in a fluidized bed reactor. Three-dimensional (3D) micro-coiled or nano-coiled materials have attracted extensive attentions because of their unique conformations and outstanding mechanical and electromagnetic properties. Reduction of FeMgAl LDH flakes can lead to the formation of layered double oxides (LDOs) with high density Fe nanoparticles embedded on both sides. Aligned double/multi-walled CNTs can synchronously grow and extend perpendicularly from both sides of the LDO flakes. With the continuous growth of the CNT arrays, the array further will assemble into CNT double helices. The intercalation of MoO42- can lower the catalyst particle size and improve its density. As a result, single-walled CNT double helices can be successfully synthesized on the MoO42- intercalated FeMgAl LDHs. The CNT double helices are with good extension characteristics and the CNT yarns in the double helices are able to carry high current . This double helical structure provides a platform towards the design of hierarchical nanocomposites that can be used in areas such as high-performance CNT yarns, nanoelectronics, magnetic devices, and energy conversion. References:  a) M.Q. Zhao, Q. Zhang, X.L. Jia, et al: Adv. Funct. Mater. 20(2010), 677â?"685; b) M.Q. Zhao, Q. Zhang, J.Q. Huang, et al: Carbon 48(2010), 3260-3270.  a) Q. Zhang, M.Q. Zhao, D.M. Tang, et al: Angew. Chem. Int. Ed. 49(2010), 3642-3645; b) M.Q. Zhao, Q. Zhang, W. Zhang, et al: J. Am. Chem. Soc. 132(2010) 14739â?"14741.
6:00 AM - CC3.32
Interaction of Protein Cages with Energetic Nanoalumina Particles
Joseph Slocik 1 Chistopher A Crouse 1 Jonathan E Spowart 1 Patrick B Dennis 1 Rajesh R Naik 1
1AFRL Dayton USAShow Abstract
Biomolecules can be used to control the interface and assembly of inorganic materials. This is particularly effective in materials science for the assembly of complex nanostructures, protein-nanoparticle interfaces, and hybrid nanocomposites as well as in the production of materials with enhanced optical, catalytic, and electrical properties. Protein cages have been explored for use in the synthesis, assembly and functionalization of nanomaterials due to their well-defined morphological and chemical composition. Site-specific modification of protein cages using genetic engineering allows for targeted functionalization and directed assembly onto surfaces. Here we describe the use of engineered ferritin protein cages designed to bind to aluminum nanoparticles (nAL). Metals such as nAL contain and release a large amount of stored energy due to their chemical composition and size. Unfortunately, energetic properties of nAL are often limited by the mass transport and diffusion distance of reactive components. These engineered protein cages can be loaded with oxidizing agents and bought in close proximity to the nAl surface, thereby leading to increased combustion kinetics and energy output from nAL. Additionally, the combination of biologically derived iron oxide with nAl is chemically equivalent to thermite and represents a new type of bio-thermite material.
6:00 AM - CC3.33
Study on ``Morphogenetic'' Materials at State Key Laboratory of Metal Matrix Composites of Shanghai Jiao Tong University
Jiajun Gu 1 Di Zhang 1 Shenmin Zhu 1 Huilan Su 1 Chuanliang Feng 1 Wang Zhang 1 Qinglei Liu 1
1Shanghai Jiao Tong University Shanghai ChinaShow Abstract
Nature generates thousands of millions of complicated and subtle structures via the process of natural selection. Many of these nano/submicrometer structures are functional units, and are far beyond the capability of human design. In the past decade, we have been focusing on using this natural wealth to fabricate a broad range of novel functional materials with morphologies of natural organisms like butterfly wing scales, egg membranes, bacteria, and plant fibers, et al. In this presentation, we will demonstrate how these natural structures can be replicated in various functional materials including oxides (ZnO, ZrO2), sulfides (CdS), and metals (Au, Ag, Cu), with their original bio-morphologies inherited. We will show as well how these novel materials can be beneficial to fields including light manipulation, gas sensing, and surface enhancement of Raman scattering, et al. Accumulated results have proven a substantial and applicable route to fully utilize the natural morphologies, yielding materials and solutions otherwise unavailable.
6:00 AM - CC3.34
Directing the Self-assembly of Nanorods for Solar Energy Applications: New Insights from Simulations at Multiple Scales
Asaph Widmer-Cooper 1 3 Phillip Geissler 2 3
1University of Sydney Sydney Australia2UC Berkeley Berkeley USA3Lawrence Berkeley National Lab Berkeley USAShow Abstract
Controlling the self-assembly of colloidal nanorods to form large-scale â?~nano-carpetsâ?T of vertically aligned rods represents a promising route towards making printable solar cells and photoelectrochemical devices. In addition to potential increases in production speed and savings in production costs, such nanostructured devices could allow for improvements in light absorption over bulk materials. Semiconductor nanorods, including heterostructures, can now be made from a wide range of materials, and cm2-scale films of aligned rods have been assembled in the laboratory. However, large films typically have defects including cracks, voids and multilayers, and are difficult to make reproducibly. This talk will present recent insights from molecular dynamics and Monte Carlo simulations into the conditions under which such films form, including the effect of the rod-rod interaction length-scale and strength, and the effect of the solvent-air and solvent-substrate interfaces. We show that the rod-rod interaction determines whether multilayer or single-layer crystals nucleate and grow in solution. Further, we find that a subtle balance between the rod-rod and rod-interface interactions determines whether nucleation occurs in solution, on the substrate, or at the air-solvent interface, and whether it occurs with the rods oriented parallel or perpendicular to the interface. We argue that the majority of assemblies formed to date are metastable kinetic products, and as such will suffer from defect and reproducibility issues. Instead, we propose a new way to make dense, uniform, and large-scale monolayer films using conditions for which they will be thermodynamically stable in solution.
6:00 AM - CC3.35
Self-assembling Polymer-peptide Conjugates and Glycosaminoglycans as Multifunctional Hierarchical Environments
Lesley W Chow 1 Cristina Gentilini 1 Molly M Stevens 1 2
1Imperial College London London United Kingdom2Imperial College London London United KingdomShow Abstract
Biological structures are hierarchically structured across multiple length scales. This complex and specific organization leads to physical properties and functions that are not achieved by the basic components alone. Cells are capable of sensing their environment from the nanoscale to macroscale making the structure-function relationships in natural tissues of great interest for designing biomaterials. In the past several decades, researchers have demonstrated the potential of electrostatically driven self-assembly as a powerful tool to achieve hierarchies across the nano-, micro-, and mesoscale. Strong interactions between polyelectrolytes and oppositely charged self-assembling peptides have been shown to induce complex formations that result in highly ordered structures. Utilising these concepts to design tunable self-assembling systems is an attractive strategy towards synthetic scaffolds that mimic the hierarchical organisation of biological tissues. We have designed and synthesized polymer-peptide hybrid molecules that self-assemble into nanostructures including nanofibres in aqueous solvents and contain peptide sequences that bind specific glycosaminoglycans (GAGs). GAGs offer a unique advantage of being highly charged polyelectrolytes that play a role in binding growth factors and regulating cellular events. Peptides were synthesised manually using standard solid phase Fmoc synthesis techniques and purified using high performance liquid chromatography (HPLC). Poly(caprolactone) (PCL) was modified with a maleimide isocyanate using reported procedures followed by coupling of the peptide via a cysteine to the maleimide group. The conjugation steps were confirmed by 1H-Nuclear Magnetic Resonance Spectroscopy (NMR), and the nanostructure morphologies were observed by transmission electron microscopy. The polymer-peptide conjugates complex with the GAGs to form hydrogels with hierarchical features across length scales. Changing the length of the hydrophobic PCL block affects the polymer-peptide nanostructure morphology, which also influences the supramolecular assembly with the GAGs. Specific binding of the GAGs introduces an additional functionality to manipulate the structural organisation. This system provides a platform to study how hierarchical structure and presentation of biologically relevant components affect cellular behaviour.  (a) Stevens MM; George JH. Science 2005, 38, 1135-1138. (b) Place ES; George JH; Williams CK; Stevens MM. Chem Soc Rev 2009, 38, 1139-1151.  (a) Capito RM; Azevedo HS; Velichko YS; Mata A; Stupp SI. Science 2008, 319, 1812-1816. (b) Carvajal D; Bitton R; Mantei JR; Velichko YS; Stupp SI; Shull KR. Soft Matter 2010, 6, 1816-1823. (c) Chow LW; Bitton R; Webber MJ; Carvajal D; Shull KR; Sharma AK; Stupp SI. Biomaterials 2011, 32, 1574-1582.  Annunziato ME; Patel US; Ranade M; Palumbo PS. Bioconj Chem 1993, 4, 221-218.
6:00 AM - CC3.5
Water-soluble Titanium Complexes as Precursors for Controlled Assembly of Hierarchical TiO2 Structures
Quang Duc Truong 1 Makoto Kobayashi 1 Hideki Kato 1 Masato Kakihana 1
1Tohoku University Sendai JapanShow Abstract
The current research has been focused on the synthesis of nanomaterials with controlled size, shape and their assembly into hierarchical structures. Herein, various TiO2 hierarchical microstructures have been fabricated by a facile hydrothermal method using water-soluble titanium complexes as precursors . Particularly, flower-like particles, titania hollow spheres, and nanorod-based microspheres have been synthesized. The growth and assembly process of these hierarchical structures were elucidated in view of capping mechanism, ligand-assisted dissolution, chelation-assisted assembly and oriented attachment. Titania materials were synthesized by a hydrothermal method using water-soluble titanium complexes as precursors and additives as shape-controlling or structure-directing reagent. Firstly, flower-like particles were synthesized using titanium-glycolate as precursor and picolinic acid as capping reagent. Secondly, hollow TiO2 spheres were fabricated using titanium-oxalate in the presence of excess ligand that played a role as etching reagent. Finally, a sulfuric acid additive was used to control the assembly of nanorod-based microspheres. The preferential adsorption of picolinic acid via chelation to Ti on (111) plane of rutile rather than (110) plane due to the matching of distances between Ti-Ti atom (6.5 Ã.) and that of the mutual Ï?-stacking between the aromatic ring (6.0-7.0 Ã.) resulted in growth of pyramidal branches in flowerlike particles. The self-assembly of microspheres was driven by the reduction of surface energy coupled with chelation effect. Ligand-assisted dissolution is responsible for the hollowing process, resulting in the formation of the hollow structures. The morphology evolution of the hierarchical microspheres followed several steps including the formation of 1D structures, assembly of the primary nanocrystals into bundles, and oriented attachment growth.  Tomita, K.; Petrykin, V.; Kobayashi, M.; Shiro, M.; Yoshimura, M.; Kakihana, M. Angew. Chem. Int. Ed., 2006, 45, 2378.
6:00 AM - CC3.6
Fabrication of Large-scale Patterned Surfaces Using an Inkjet-print Self-assembly Method
Sung Hyuk Hong 1 Hyun Choi 1 Dong June Ahn 1
1Korea University Seoul Republic of KoreaShow Abstract
The pattern fabrication of the self-assembled monolayers (SAMs) is important to produce more delicate functionality by the spatial distribution of functional groups on various surfaces. Inkjet printing is versatile in aspects of high speed, relatively simple process, low cost, compatibility with a wide range of substrates, and ability to deposit very small droplets. Recently the inkjet technology has been recognized as one of the most promising technologies for soft electronics. However, the inkjet-assisted patterning needs more fundamental understandings to be applied in wider fields. In this work, we report fast and large-area SAM pattern fabrication controllable by an inkjet-print self-assembly method which combines inkjet printing and SAM techniques. By means of controlling process conditions such as solution concentration, dispensing speed, and humidity etc., optimized patterns were well produced. The resulting inkjet-print SAM patterns of 3-aminopropyltriethoxysilane and 3-triethoxysilylpropyldiethylenetriamine with surrounding octadecyltriethoxysilane SAM were confirmed by AFM, FTIR spectroscopy and contact angle meter. These inkjet-print SAM patterns were also applied to further selective immobilization of various functional organic and inorganic nanomaterials.
6:00 AM - CC3.7
Self-assembled beta;-sheet Peptide Hybrid Poly (gamma;-glutamic Acid) Hydrogels
David E Clarke 1 2 E. Thomas Pashuck 1 2 Cristina Gentilini 1 2 Molly M Stevens 1 2
1Imperial College London London United Kingdom2Imperial College London London United KingdomShow Abstract
Tissue engineering strategies typically utilize either peptide or polymer hydrogels as bio-mimetic scaffold carrier materials . Hydrogels provide mechanical support for cells and can easily be combined with bioactive moieties to help elicit a desired cellular response. Polymer hydrogels have tailorable mechanical properties but often suffer from being synthesised from synthetic monomers and having to be polymerized in situ . Peptide based hydrogels are formed via self-assembly which gives rise to very unique properties and results in them having the ability to be used as injectable systems, with gelation occurring simply through the addition of salts . Furthermore, they degrade into natural occurring amino acids and biomolecules can be easily incorporated which offers advantages in terms of bioactivity, but fundamentally they suffer from quick degradation rates and have low failure strains3. Here we present a novel and alternative hybrid polymer-peptide gel system consisting of a poly (Î³-glutamic acid) (Î³-PGA) polymer network physically cross-linked via grafted self-assembled Î²-sheet peptide sequences. Î³-PGA is a naturally occurring enzymatically degradable homo-polyamide, it is highly biocompatible and water soluble . This system provides a gel made entirely from natural peptide bonds, with a polymer network providing tunable mechanical properties and predicted high failure strains. Biomolecules can easily be incorporated and tailored for a given application via abundant and unmodified â?"COOH groups situated on the polymer backbone and also, being designed to gel through self-assembly it can be used as an injectable system. Î²-sheet peptide sequences were synthesised using a manual solid phase Fmoc peptide synthesis technique. Purity was confirmed by HPLC and Mass Spectroscopy. The peptide sequences were grafted to Î³-PGA in the presence of diisopropylcarbodiimide and the degree of peptide conjugation was estimated by HPLC. The hybrid polymer-peptide material was dissolved in water and the solution pH increased by addition of NaOH, causing immediate self-assembly and the formation of a gel. Rheological experiments were used to investigate the mechanical properties, and to verify the predicted high failure strains of the hybrid hydrogels. These reached up to 40% strain before failure, eclipsing typical failure strains of peptide self-assembled hydrogels. Following repeated material failures the hybrid polymer-peptide gel was left to re-assemble and managed to recover 90% of its storage modulus. The secondary structure and pH responsivity of the hydrogels was observed through circular dichroism and Î²-sheet formation was confirmed via fluorescent spectroscopy after binding to Thioflavin T.  Place, Evans, Stevens. Nature Materials 2009.  Burdick, Anseth. Biomaterials 2002.  Greenfield, Hoffman, Olvera de la Cruz, Stupp. Langmuir 2010.  Kubota H, Nambu, Endo. J Polym. Sci. Part A Polym. Chem 1993.
6:00 AM - CC3.9
A Computational Approach towards Substrate Tailored Morphology in Organic Photovoltaics
Spencer Pfeifer 1 Olga Wodo 1 Baskar Ganapathysubramanian 1 2
1Iowa State University Ames USA2Iowa State University Ames USAShow Abstract
Current progress in self-assembly and material genomics has spawned a growing interest in morphology control for higher efficiencies and structural stability in thin film devices. Further, recent experimental evidence suggests that substrate patterning may be an elegant means for obtaining this desired control. When applied to the field of organic photovoltaics, substrate patterning may provide a promising approach in fabricating a more tractable donor/acceptor composition gradient, and therefore, a higher efficiency device. However, current challenges in experimental efforts include the inability to decipher the complexities of morphology evolution as well as limitations on resources and time. Thus, the use of a computational framework, to predict morphology evolution during solvent-based fabrication techniques, will add significant value to the predominantly experimental community. Developed for high throughput analysis of morphology evolution during solvent-based fabrication of organic solar cells, this framework includes modeling of evaporation-induced and substrate-induced phase separation. In this way, we can successfully quantify the effects of substrate patterning on morphology evolution. In particular, we are interested in examining various one and two-dimensional patterning motifs aimed towards constructing a detailed phase diagram. Subsequently, this provides a quantitative means for understanding morphology evolution undergoing substrate induced phase separation, and a recipe for self assembly control. These developments yield detailed tuning capabilities for producing morphologies that display favorable intrinsic characteristics in the context of organic solar cells, and thereby produce higher efficiency devices.
CC1: Hierarchical Biointerface and Building Block
Tuesday AM, April 10, 2012
Moscone West, Level 3, Room 3006
9:30 AM - *CC1.1
Protocells: Nanoporous Nanoparticle Supported Lipid Bilayers for Targeted Delivery of Multicomponent Cargos to Cancer
C. Jeffrey Brinker 1 3 5 Carlee E Ashley 2 5 Eric C Carnes 3 5 Robert E Castillo 4 3 Katharine E Epler 4 3 David P Padilla 4 Jason L Townson 4 Walker Wharton 5 6
1Sandia National Laboratories Albuquerque USA2Sandia National Laboratories Livermore USA3University of New Mexico Albuquerque USA4University of New Mexico Albuquerque USA5University of New Mexico Albuquerque USA6University of New Mexico Albuquerque USAShow Abstract
Encapsulation of drugs within nanocarriers that selectively target malignant cells promises to mitigate side effects of conventional chemotherapy and to enable delivery of the unique drug combinations needed for personalized medicine. To realize this potential, however, targeted nanocarriers must simultaneously overcome multiple challenges, including specificity, stability and a high capacity for disparate cargos. We recently developed a new class of hierarchical nanocarriers termed protocells that synergistically combine features of mesoporous silica nanoparticles and liposomes. Fusion of liposomes to a spherical, high-surface-area, nanoporous silica core followed by modification of the resulting supported lipid bilayer (SLB) with multiple copies of a targeting peptide, an endosomolytic peptide and PEG results in a nanocarrier construct (the â?~protocellâ?T) that, compared with liposomes, the most extensively studied class of nanocarriers, improves on capacity, selectivity and stability and enables targeted delivery and controlled release of high concentrations of multicomponent cargos (chemotherapeutic drugs, siRNA, dsDNA, toxins, etc.) within the cytosol or nucleus of cancer cells. Specifically, owing to its high surface area (>1000 square meters per gram), the nanoporous silica core possesses a higher capacity for therapeutic and diagnostic agents than similarly sized liposomes. Furthermore, owing to the substrateâ?"membrane adhesion energy, the core suppresses large-scale membrane bilayer fluctuations, resulting in greater stability than unsupported liposomal bilayers. Interestingly, the nanoporous support also results in enhanced lateral bilayer fluidity compared with that of either liposomes or SLBs formed on non-porous particles. We show the enhanced fluidity yet stability of the SLB enables dynamic reconfiguration of the surface allowing membrane bound ligands to engage in complex multivalent interactions with the target cell. The synergistic combination of materials and biophysical properties organized over several hierarchical length scales enables high delivery efficiency and enhanced targeting specificity with a minimal number of targeting ligands, features crucial to maximizing specific binding, minimizing nonspecific binding, reducing dosage, and mitigating immunogenicity.
10:00 AM - *CC1.2
Self-Assembly of Magnetic Colloids to Responsive Photonic Nanostructures
Yadong Yin 1
1University of California Riverside USAShow Abstract
In this presentation I will introduce our recent advances in the self-assembly of superparamagnetic colloidal building blocks for the fabrication of magnetically responsive photonic nanostructures. The superparamagnetic iron oxide colloidal particles are essentially self-assembled clusters of small nanocrystals that are synthesized by using a high temperature hydrolysis reaction. Another self-assembly process occurs when these superparamagnetic colloids are exposed to external magnetic field, allowing the formation of chain-like nanostructures with regular interparticle spacing of a few hundred nanometers along the direction of the external field so that the system strongly diffracts visible light. The balance between attraction (magnetic dipole interaction) and repulsion (electrostatic force) dictates interparticle spacing and therefore optical properties. By changing the relative strength of these two forces, we can tune the peak diffraction wavelength over the entire visible spectrum. We demonstrate a number of interesting applications ranging from color displays to security devices, and color printing that are made possible by the taking advantage of the fast, reversible response and the feasibility for miniaturization of these magnetic responsive photonic nanostructures.
10:30 AM - CC1.3
Solution Self-assembly of Superparamagnetic Nanoparticles into Superlattices
Sara Mehdizadeh Taheri 1 Sabine Rosenfeldt 1 Markus Drechsler 1 Beate Foerster 1 Peter Boesecke 2 Stephan Foerster 1
1University of Bayreuth Bayreuth Germany2ESRF Beamline ID2 Grenoble Cedex FranceShow Abstract
Solution self-assembly of superparamagnetic nanoparticles is driven by short-ranged magnetic dipolar interactions. Interesting situations occur if the sizes of the nanoparticles are so small that they become comparable to the range of magnetic interactions. In this regime nanoparticle self-assembly delicately depends on size, shape, thickness of the stabilization layer, and strength of external magnetic fields. We show by using dynamic light scattering, cryo-TEM, cryo-SEM and synchrotron small-angle x-ray scattering, that small cubic nanoparticles with thin stabilization layers self-assemble into very long strings and highly ordered meso-crystals of sizes of seveal micrometers, that can be oriented in external magnetic fields. Spherical nanoparticles and cubic nanoparticles with thick stabilzation layers do not self-assemble under similar conditions, allowing control of the magnetically induced self-assembly process via size, shape and layer thickness of the nanoparticles. Control of magnetic self-assembly of nanoparticles is vital for their use in magnetic resonance imaging, where solution self-assembly and aggregation of nanoparticles has to be controlled to maximize relaxivities and thus imaging contrast. We further show that the attachment of brush-like polymer layers completely suppresses nanoparticle aggregation in nanocomposites. This opens for the firs time a versatile route to fully miscible nanocomposites. We demonstrate that highly filled nanocomposites can be made that show ordering of nanoparticles into well-defined fcc-lattices. Control of interparticle distance is possible via the molecular weight of the attached polymer chains (1). S. Fischer, A. Salcher, A. Kornowski, H. Weller, S. FÃ¶rster, Angew. Chem. Int. Ed. 50, 7811 (2011)
10:45 AM - CC1.4
Hierarchical Assembly of Magnetic L10-ordered FePt Nanoparticles in Block Copolymer Thin Films: Towards Potential Future Bit-patterned Magnetic-storage Media
Karim Aissou 1 Guillaume Fleury 1 Gilles Pecastaings 1 Georges Hadziioannou 1 Thomas Alnasser 2 Steacute;phane Mornet 2 Graziella Goglio 2
1Laboratoire de Chimie des Polymegrave;res Organiques (LCPO) Talence cedex France2Institut de Chimie de la Matiegrave;re Condenseacute;e de Bordeaux (ICMCB) Pessac FranceShow Abstract
The magnetic properties derived from the nanoscale self-assembly of poly(styrene-block-ethylene oxide) (PS-b-PEO) copolymer thin films blended with L10-ordered FePt nanoparticles (NPs) are investigated. In this communication, we reported the morphological change induced by the introduction of FePt nanoparticles on the phase behavior of PS-b-PEO thin films. We find that the increase of the unit cell due to the presence of nanoparticles leads to close-packed planes of spheres with an ABAB stacking which are more stable than the cylinder phase observed for the neat PS-b-PEO copolymer thin films. The stability of a square-packing phase for a particular film thickness is also discussed since this morphology is advantageous for microelectronic applications. Macroscopic study of the magnetic property reveals a distinct hysteresis with a coercivity value of about 100 Oe at 300K, which constitutes the first example of block copolymer/nanoparticle nanocomposite thin films having magnetic property at room temperature. At the nanoscopic scale, magnetic signals observed on MFM images indicate, in accordance with TEM images, that L10-ordered FePt NPs functionalized with short dopamine-terminated-methoxyl poly(ethylene oxide) chains are localized within the spherical PEO domains. In order to increase the 2D long-range order of the sphere array, we also present self-assembled PS-b-PEO/FePt nanocomposite thin films confined in microfabricated polymer trenches. The use of patterned substrates permits to decrease the density of dislocations and disclinations which favor the accumulation of nanoparticles (small aggregates) within their core defects in order to minimize the conformational entropy loss associated with the PEO chain stretching. An important application of this work extends to potential future bit-patterned magnetic-storage media.
11:30 AM - *CC1.5
Designed Assembly of Uniform-sized Nanoparticles for Multifunctional Medical Applications
Taeghwan Hyeon 1 Ji Eun Lee 1 Daishun Ling 1 Chang Young Song 1
1Seoul National University Seoul Republic of KoreaShow Abstract
Integration of diverse nanostructured components into single nanoparticle system enables the development of multifunctional nanomedical platforms for multimodal imaging or simultaneous diagnosis and therapy, which provides synergistic advantages compared to individual component materials, such as real-time non-invasive monitoring of drug delivery and biological responses to the therapy. We reported on the fabrication of monodisperse magnetite nanoparticles immobilized with uniform pore-sized mesoporous silica spheres for simultaneous MRI, fluorescence imaging, and drug delivery. We synthesized hollow magnetite nanocapsules and used them for both the MRI contrast agent and magnetic guided drug delivery vehicle. We reported the fabrication of novel alginate capsule-in-capsules (CICs) containing iron oxide and gold nanoparticles and human pancreatic islets for simultaneous immunoprotection and multimodal imaging.
12:00 PM - *CC1.6
Hybrid Biomaterials Based on Peptide-polymer Conjugates
Ting Xu 1
1University of California, Berkeley Berkeley USAShow Abstract
Peptides and proteins are hierarchically structured nanoscale assemblies with well-defined atomic-level structures. As materials, they possess structural and catalytic functionalities that are unmatched by any synthetic counterparts to date. Hybrid biomaterials based on synthetic polymers and natural building blocks have the potential to combine the advantages of both components and overcome the inherent limitations, such as the ease of degradation, loss of functionality, and difficulty in processing for biomolecules. With recent advances in our fundamental understanding of protein science, especially in designing peptide/protein sequences to achieve properties similar or superior to their natural counterparts and in developing synthetic methods to modify proteins in a controlled manner, these building blocks present numerous opportunities to create soft materials to meet current challenges in life science, energy and environment. I will discuss our recent efforts in design and synthesis of amphiphlic peptide-polymer conjugates toward engineering modular organic nanoparticles as nanocarriers. Stable, multi-functional organic nanoparticles that combine long in vivo circulation, the ability to cross vessel walls to reach tumor tissues and controlled disassembly/degradation for eventual clearance will have a significant impact in nanomedicine. However, it remains a significant challenge to simultaneously control the nanoparticle size in the range of 10-30 nm, enhance particle stability and tailor disassembly at the timescale suitable for nanocarriers. We have advanced this goal by designing a new family of amphiphiles based on coiled-coil 3-helix bundle forming peptide-polymer conjugates. The resultant monodispersed nanoparticles are composed of subunits, < 4 nm in size, that form a highly stable 15-17 nm diameter particle and demonstrate an in vivo circulation half life-time of 28 hrs, minimal accumulation in the liver and spleen and effective urinary clearance. Based on these studies, I will discuss some opportunities this new family of soft matter presents as well as challenges to advance this emerging field.
12:30 PM - CC1.7
Magnetically Responsive Colloidal Photonic Crystals
Le He 1 Yadong Yin 1
1UC Riverside Riverside USAShow Abstract
Magnetic field is as an effective stimulus to guide the rapid assembly of superparamagnetic colloidal building blocks into one-dimensional dynamic photonic chains within one second. Each chain, with periodical interparticle spacing in the range of 100 to 200 nm, acts as the smallest 1D photonic unit and strongly diffracts visible light. The structural color of the photonic structures can be dynamically modulated across the whole visible light range by changing the interparticle separation or the orientation using an external magnetic field. We also demonstrate the assembly of superparamagnetic Fe3O4@SiO2 particles in a spatially patterned magnetic field, which allows one to change the orientation of the particle chains, dynamically producing a high contrast in color patterns. In principle, magnetic fields can be used to dynamically modulate the color of each pixel, making our magnetically responsive photonic system a new platform for chromatic applications, such as reflective color display, antifraud, camouflage.
12:45 PM - CC1.8
DNA -based Dual-spring Cross Shaped Nanoactuator
Alexander Mo 1 Preston Landon 2 Ratnesh Lal 1 2
1UCSD La Jolla USA2UCSD La Jolla USAShow Abstract
DNA is an attractive platform for nanotechnology applications because of its size, specificity, and designability. However constructing DNA-based platform that can do work is difficult. We have developed a DNA-based cross-shaped nanoactuator system that cycles between an extended and contracted confirmation relying on strand displacement reactions. The actuator contains 4 structural strands with two unique DNA â?ozipperâ? sequences. Each zipper sequence employs traditional adenosine-thymine nucleotides as well as non-traditional inosine-cytidine nucleotides. The I-C bond consists of only 2 hydrogen bonds as opposed to the typical 3 hydrogen bonds found in G-C bonds. The actuator is extended by inserting two ssDNA which are the natural complements to the zipper sequences. The natural complements have a stronger binding affinity to one side of the zipper than both zipper strands have to each other, thus unraveling and allowing the actuator to extend. The two contraction strands contain sequences which are a natural complement to parts of the opening strand. When they bind to the extension sequences, the zippers are able to rebind and this contracts the actuator. Proper assembly and function of the devices was confirmed using fluorescent DNA gel electrophoresis, AFM imaging, and time-lapsed fluorescence.
Symposium OrganizersHongyou Fan, Sandia National Laboratories
Donghai Wang, Pennsylvania State University
Earl Stromberg, Lockheed Martin Aeronautics
Ilhan Aksay, Princeton University
Symposium Support Oak Ridge National Laboratories
Sandia National Laboratories
CC5: Design and Characterization of Hierarchical Nanostructures
Wednesday PM, April 11, 2012
Moscone West, Level 3, Room 3006
2:30 AM - *CC5.1
Hierarchical Self Assembly of Facetted Particles
Sharon C. Glotzer 1
1University of Michigan Ann Arbor USAShow Abstract
Hard particles are known to organize due to entropy alone, and simple crystals, liquid crystals, and even quasicrystals have been reported in the literature. However, the role of entropic forces in connection with building block shape is not well understood. We present the results of a comprehensive computer simulation study of the thermodynamic self-assembly and packing of facetted particles. We report hierarchical assembly of both disordered and ordered structures for certain facetted shapes. We show how the self-assembled structures can be understood as a tendency for the particles to maximize alignment of their facets, which can be generalized as directional entropic forces.
3:00 AM - *CC5.2
Meso-origami: Folding and Assembly of Single and Multilayer Graphene Sheets and Amyloid Protein Filaments
Markus J Buehler 1 Steven W Cranford 1 Max Solar 1 2
1MIT Cambridge USA2MIT Cambridge USAShow Abstract
In part I of this talk on meso-origami we present studies of hierarchical assemblies of graphene. Graphene is the ultimate thin film with a single layer atomic layer thickness and features unique electronic, thermal, and mechanical properties. The flexibility and strong attraction between graphene layers promotes the formation of self-folded nanostructures, which can be assembled into various hierarchical geometries. In this talk we present an overview of recent atomistic and continuum modeling of tearing, folding and assembling graphene sheets into functional materials. We study the self-folding of mono- and multilayer graphene sheets, utilizing a coarse-grained hierarchical multiscale model derived directly from atomistic simulation. We extend the analysis to a systematic study of the conformational phase diagram of graphene sheets, and we derive a conformational phase diagram for rectangular graphene sheets, defined by their geometry (size and aspect ratio), boundary conditions, and the environmental conditions such as supporting substrates and chemical modifications, as well as changes in temperature. We discover the occurrence of three major structural arrangements in membrane, ribbon, and scroll phases as the aspect ratio of the graphene nanoribbon increases. In part II we present an analysis of folding and assembly of amyloid protein materials at varied scales. Amyloids are highly organized protein filaments, rich in beta-sheet secondary structures that self-assemble to form dense plaques in brain tissues affected by severe neurodegenerative disorders (e.g. Alzheimerâ?Ts Disease). Identified as natural functional materials in bacteria, in addition to their remarkable mechanical properties, amyloids have also been proposed as a platform for novel biomaterials in nanotechnology applications including nanowires, liquid crystals, scaffolds and thin films. We use a coarse-grain model to analyze the competition between adhesive forces and elastic deformation of amyloid fibrils, focused on the formation of self-folded nanorackets and nanorings. We investigate the effect of varying the interfibril adhesion energy on the structure and stability of self-folded nanorackets and nanorings and demonstrate that such aggregated amyloid fibrils are stable in such states even when the fibril-fibril interaction is relatively weak, suggesting a strong propensity towards aggregation, given that the constituting amyloid fibril lengths exceed a critical fibril length-scale of >100 nm. Our model enables the analysis of large-scale hierarchical amyloid plaques and presents a new approach to engineer the adhesive forces responsible of the self-assembly process of amyloid nanostructures. We conclude with a discussion of universal principles that hold for both graphene and protein based assembly into hierarchical structures, and outline opportunities for the design of mutable materials.
3:30 AM - CC5.3
Self-assembly of Artificial Microtubules
Mark Stevens 1 Shengfeng Cheng 1
1Sandia National Labs Albuquerque USAShow Abstract
Biological materials often have a hierarchical structure which enables complex functionality. Biopolymers such as microtubules have monomers which are proteins that contain a rich variety of features incorporated into the basic building block. In development of materials that mimic aspects of natural systems, we will need to develop basic macromolecular building blocks that have a range of features. A promise of nanoscience is the creation of such complex nanoparticles, after all proteins are nanoparticles. We are working to understand the fundamental features of the monomers that will yield the geometry and dynamic properties of interest. In particular the focus of the modeling effort is determining design principles for assembly of tubular structures from monomers that mimic microtubules formed from the protein tubulin. We will discuss the results of simulations that show our monomer models can self-assembled into tubular structures including helical geoemetry without a chiral character in the monomeric building block. The role of the interactions in the dynamic assembly is critical in the assembly process with respect to defect tolerance. We will present a structure diagram of the different structures that form as a function of the interaction parameters.
3:45 AM - CC5.4
Simulation Study of Self-limited Self-assembly of Polydisperse Nanoparticles into Monodisperse Supraparticles
Trung Dac Nguyen 1 Yunsheng Xia 2 Zhiyong Tang 2 Sharon C Glotzer 1 3 Nicholas A Kotov 1 3
1University of Michigan Ann Arbor USA2National Center for Nanoscience and Technology Beijing China3University of Michigan Ann Arbor USAShow Abstract
We investigate the self-assembly of polydisperse inorganic nanoparticles (CdSe, CdS, ZnSe and PbS) into highly uniform supraparticles with a core-shell morphology. The self-assembly process is believed to be self-limiting due to the balance between van der Waals attraction and Coulombic repulsion as observed in experiments and further elaborated by our simulations. The uniform supraparticles are shown to be stable for a wide range of density rather than kinetically trapped. Our results further reveal that the remarkable nanoparticle polydispersity leads to the core-shell morphology of the supraparticles. The generic nature of the governing interactions suggests great versatility in the composition, size and shape of the constituent building blocks, and allows for a large family of self-assembled structures, including colloidal crystals.
4:30 AM - *CC5.5
Hierarchical Materials Based on Functionalized Graphene Sheet Directed Nucleation and Self-assembly
Jun Liu 1
1PNNL Richland USAShow Abstract
Molecularly directed nucleation and self-assembly is a fundamental mechanism in biology to control the structure and property of biomaterilas and biominerals. In this paper, by using a combination of theoretical and experimental approaches, we demonstrate that functionalized graphene sheets (FGS) can be used as a new class of molecular templates to direct the nucleation and self-assembly and produce bulk, three-dimensional nanocomposite materials. We show that the interfacial energy controls the crystalline phase, as well as the nucleation and nucleation density. We further demonstrate that the FGS molecular templates can control the kinetics of complex 3D architectures. The electrochemical properties of the new materials are investigated for energy storage (batteries) and conversion (fuel cell) applications.
5:00 AM - CC5.6
Latex Based Templated Assembly of Carbon Nanotube and Graphene Based Functional Materials
Izabela Jurewicz 1 Ronan J Smith 2 Jonathan N Coleman 2 Joseph L Keddie 1 Alan B Dalton 1
1University of Surrey Guildford United Kingdom2Trinity College Dublin Dublin IrelandShow Abstract
Focused studies of one-dimensional carbon nanotubes (CNTs) and two dimensional graphene are driven by their wide-ranging potential applications. However, utilizing the often-extraordinary physical and chemical properties in macroscale systems remains a real bottleneck to generalized application. There is a real need to develop practical technologies for transforming the as-produced CNTs and graphene  into materials or integrated assemblies with properties that are both fundamentally interesting and useful for applications. A novel method for tailoring the properties of nanocomposites by controlling the way in which nanomaterials are ordered, using colloidally derived polymer latex crystals is described. This simple colloidal deposition process facilitates the formation of highly ordered multi-arrays of polymer particles, which act as a template for the assembly of CNTs into three-dimensional hexagonal patterns and thus creates the possibility to overcome problems with filler distribution. The individual particles deform into rhombic dodecahedra, which is mainly driven by capillary forces as the system dries. Nanotubes are assembled and positioned at interstitial sites between the polymer particles resulting in a honeycomb-like arrangement. The use of this facile and elegant technology allows for the formation of robust mechanical composites with electrical percolations markedly lower than witnessed in more conventional polymer composites. The resulting composites maintain their electrical properties but can undergo large strain before failure. More surprisingly, when the stress is released the sample return to its original shape before deformation, while maintaining the inherent structural arrangement of nanotubes at interstitial points. The templated assembly of CNTs using plasticized colloidal crystals as described here can ultimately be generic for assembling a range of other low-dimensional nanostructures. Moreover, combining our surfactant-assisted-plasticization method with other controllable parameters, such as polymer-particle size and polymer type, should provide excellent control over structureâ?"property relationships for specific applications. In particular such highly ordered assemblies are expected to find applications in optical technologies.  Y. Hernandez, et.al. Nat. Nanotechnol. 2008, 3, 563.  Jurewicz et.al, Macromol. Rap. Comm. 2010, 31, 585  Jurewicz et.al, J Phys Chem B. 2011, 115, 6395  Worajittiphon et.al, Adv. Mater. 2010, 22, 5310
5:15 AM - CC5.7
Hierarchical Crystal Assembly of Porous Coordination Polymers toward Fabricating Highly Oriented Freestanding Membranes by Langmuir-Blodgettry
Manuel Tsotsalas 1 2 Shuhei Furukawa 1 2 Susumu Kitagawa 1 2
1Kyoto University Kyoto Japan2Japan Science and Technology Agency Kyoto JapanShow Abstract
Porous Coordination Polymers (PCP), with their ordered nanoporous system and large surface area are very attractive for numerous applications, which involve controlled molecular transport properties. To fully exploit their potential, a straightforward processing method to deposit the PCP crystals on various substrates and to create freestanding membranes with controlled pore orientation is highly desirable. Here we report a strategy to self-assemble PCP crystals into two-dimensional monolayers using Langmuir Blodgettry. This approach allows the deposition on various substrates over several square centimeters, uniformly and with controllable density of the crystals. Additionally we show that by controlling the morphology of the crystalline building block we can program their orientation on the substrates. By using a copper grid as substrate these assemblies can also be fabricated as freestanding sheets. This approach represents a very simple and scalable processing method to translate the orientation of the channel network from the individual crystal to the macroscopic scale and can help to incorporate this interesting class of materials within advanced hierarchical systems.
5:30 AM - CC5.8
Nucleation and Growth of Metal Oxide on Functionalized Surfaces: A Theoretical Insight
Maria Sushko 1 Donghai Mei 1 Jun Liu 1
1Pacific Northwest National Laboratory Richland USAShow Abstract
Controlling the growth of inorganic materials on organic templates poses many challenges, but also opens vast opportunities for materials design. One of the important and yet unresolved questions is how does mineral growth affect the template structure. We present the theoretical study of titania nanoparticle nucleation and growth on functionalized graphene surfaces and on surfactant templates supported on graphene surface. We show that graphene functionalization, which modifies its interfacial chemistry, determines polymorph selection for nucleating titania nanoclusters. During the growth process on surfactant templates titania nanocrystals are initially confined between surfactant hemicylindrical micelles until they reach a critical size. Subsequent growth leads to at first partial and then complete rearrangement of the template structure to a monolayer configuration, which changes the mechanism of nanoparticle growth from predominantly thermodynamic to predominantly kinetic. The critical nanoparticle size can be controlled by controlling the stability of surfactant template with symmetric and asymmetric electrolytes. These results pave the way for designing synthesis pathways for nanocomposite materials with well-defined architectures.
CC6: Poster Session: Hierarchical Nanostructure III
Wednesday PM, April 11, 2012
Marriott, Yerba Buena, Salons 8-9
9:00 AM - CC6.1
Hierarchical Ordering of Polymer Stripes and Au Films Mixture Wrinkles
Wei Han 1 2 Myunghwan Byun 2 Zhiqun Lin 1
1Georgia Institute of Technology Atlanta USA2Iowa State University Ames USAShow Abstract
The pattern of periodical poly(methyl methacrylate) (PMMA) stripes, covered with gold thin film, was fabricated via controlled evaporative self-assembly combined with ion sputtering. An intriguing two-stage wrinkling (thermal expansion-induced wrinkles and mechanically-driven wrinkles), as well as complex wrinkling instability patterns, were observed, due to the different mechanical properties of two regions (Au only and Au/PMMA bilayer). The nanomechanical properties of the composite structure were also investigated based on the buckling instability method.
9:00 AM - CC6.10
Bio-inspired Redundant Nanofluidic Networks for Nanoparticle Transport and Separation
Nathan Francis Bouxsein 1 Amanda Carroll-Portillo 2 Marlene Bachand 1 Darryl Sasaki 3 George D Bachand 1
1Sandia National Laboratories Albuquerque USA2University of New Mexico Albuquerque USA3Sandia National Laboratories Livermore USAShow Abstract
Synthetic interconnected nanofluidic networks formed from a simple cooperative interaction between phospholipid vesicles and motor protein-based transport have been fabricated on the millimeter scale. These lipid networks possess inherent redundancies useful for high-fidelity materials transport via lipid surface fluidity or contained flow within the continuous connected tubules. The synthetic networks highly resemble the interconnected and reticulated lipid structures of the endoplasmic reticulum found throughout the cytosol. While these natural structures provide a matrix for organizing membrane constituents, the lumen (i.e. interstitial space) represents a continuous nanofluidic network for the transport of proteins and small molecules throughout the cell. Additionally, we create structures which mimic biological membrane (or tunneling) nanotubule connections, commonly used for intercellular signaling and transport(1). In our system, the energy-driven motility of microtubule filaments by surface bound kinesin motors provides an extracting force on the membranes of multilamellar liposomes, connected to the microtubules by biotin-streptavidin bonds, and results in the formation of highly bifurcated networks of lipid nanotubules. Because microtubules can translocate over a large two-dimensional surface in this inverted style assay, the total nanofluidic network size is only limited by microtubule trajectories, microtubule surface density, molecular motor energy source (ATP) and total amount and physical properties of the source liposomes. These parameters were varied systematically to tune the frequency of network bifurcation to increase or decrease the network redundancy. The system can thus accommodate critical failures between junctions without affecting material transport and separation. Additionally, we show that while nanoparticles bound to the surface of the nanotubes undergo diffusive transport that closely follows a 1D process, the application of external stimuli can concentrate and separate nanoparticles in a directed fashion. Overall, this incredibly flexible system can be used to help elucidate properties of the relatively complex transport and communication processes seen in vivo and additionally, can be used as an â?oon-chipâ? platform for materials capture and transport. * Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. 1. Rustom, A., Saffrich, R., Markovic, I., Walther, P. & Gerdes, H.-H. Nanotubular highways for intercellular organelle transport. Science (New York, N.Y.) 303, 1007-10 (2004).
9:00 AM - CC6.11
Directed Assembly of Stable, Oriented Chain Arrays of Bimetallic Janus Particles
Shengrong Ye 1 R. Lloyd Carroll 1
1West Virginia University Morgantown USAShow Abstract
Assembly of anisotropic particles into useful structures holds great potential for applications in photonics, electronics, optical and biological sensing. In most cases, however, these new building blocks may not naturally assemble into any desired structures. It is crucial to find a way that allows unprecedented control over the interaction force exerted on every individual particle. Such a technique for directed particle assembly is under development through application of external stresses such as electric field, magnetic field, and variety of templating approaches. Bimetallic Janus Particles (BJPs), composed of colloidal particles coated with differing metals on opposite hemispheres, have been our focus due to their unique properties. In particular, surface modification leads to a wide selection library of Janus particles with high tunability in conductivity, band gap, refractive index, etc. Previous work showed a solution based specific assembly of BJPs into periodic arrays of chain structures. However, the formed chain structure arrays were not stable during the process of phase transition. In this work, we will demonstrate a new approach to retain the resulting chain structures, which allows controlling the density and orientation of the assembled structures for future optical behavior demonstration.
9:00 AM - CC6.12
Highly Facile Solvent and Temperature-based Methods for Assembling Vertically-aligned CdSe Nanorod Arrays in Solution
Albert M Hung 1 Taesook Oh 2 Nathan A Konopliv 1 Jennifer N Cha 1
1UCSD La Jolla USA2UCSD La Jolla USAShow Abstract
Large-area films of vertically-aligned semiconductor nanorods are potentially useful as active materials in optoelectronic devices. We have demonstrated highly facile approaches to reversibly assembly CdSe nanorods into ordered, aligned arrays in solution. The preferential evaporation of a "good" solvent from a binary solvent mixture resulted in a continuous decrease in solvent quality and induced nanorod assembly by solvophobic interactions. A similar effect was achieved by cooling down a nanorod suspension from elevated temperature in a marginal solvent. The self-assembled structures consisted of free-floating sheets up to 24 Î¼m in diameter of hexagonally close-packed nanorods and were believed to form by a nucleation and growth mechanism. These platelets could be directly drop-cast from solution onto a substrate and rapidly dried to obtain a large-area film of vertically aligned nanorods. This assembly method was robust and effective over a wide range of solvents and nanorod concentrations with no need for applied electric fields, extensive control of drying conditions, exceptionally monodisperse nanorods, or high concentrations of additives. Modulating inter-particle interactions in this manner may also be useful for assembling other nanorod or nanoparticle systems.
9:00 AM - CC6.13
Large-Scale Hierarchal Self-assembly of Discrete Clusters of Nano-/Micro-spheres
Mostafa Bedewy 1 A. John Hart 1
1University of Michigan Ann Arbor USAShow Abstract
Bottom-up fabrication of hierarchal structures made from nano- and micro-scale building blocks is sought for many applications including plasmonics, photonics, and phononics. In particular, discrete clusters of metal nanoparticles have been used as fano resonant biosensors; however, the fabrication process typically involves e-beam lithography which is time-consuming and limited to planar shapes. We herein demonstrate a methodology to create large scale patterns of islands of self-assembled particles from droplets confined on patterned microposts. We investigated different methods of breaking macroscopic droplets into femto-litre droplets of water-based suspensions of polymer and metal spheres. We use templated substrates with physical templates composed of either negative recesses, or positive features to deterministically control placement of the assembled particle clusters. Also, we tailor the surface energy of the top surface of raised features (posts) to become more hydrophilic in order to promote the entrapment of sessile droplets during a roll-to-roll compatible blade casting process. We measure the statistical distribution of cluster sizes on identical post arrays, and study the effect of the post geometry, inter-post spacings, and surface treatment on the resulting droplet size and number of particles per cluster. The high degree of control on uniformity as well as the deterministic nature of this approach is promising for scalable fabrication of plasmonic sensors.
9:00 AM - CC6.15
Synthesis and Characterization of Hierarchically Porous Carbon Materials and Its Application in Energy Storage
Donghai Wang 1 Tianren Xu 1 Jinkui Feng 1 Mikhail Gordin 1 Shuru Chen 1 Zhongxue Chen 1
1Pennsylvania State University University Park USAShow Abstract
Porous carbon has been widely used as electrode materials in energy storage applications due to its high surface area and high electronic conductivity. The lithium-sulfur (Li-S) battery has attracted great attention as a next-generation energy storage device, owing to its extremely high theoretical energy density. Several types of porous carbon materials have been proposed to synthesize carbon-sulfur nanocomposites to improve contact between sulfur and carbon and therefore the conductivity of the elect