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Please put your posters up as soon as possible in the morning Authors are expected to be by their posters, Even number posters are in the morning session and odd number posters are in the afternoon session. Poster 1 Seed-Mediated Growth of Uniform Arrays of Metal
Nanoparticles on Silicon Wafer Fabrication of metal nanoparticle arrays with controlled particle size, shape, and distribution has been attracting a lot of research interests in recent years, due to their potential applications in catalysis, information storage, sensors, and photonics. Although excellent progress has been made towards shape and size control of nanoparticles in the solution phase, research on the growth of particles supported on solid substrate is still evolving. A common limitation in previous studies has been the lack of control over particle size and distribution. In this work, we demonstrate a simple synthetic route to fabricate arrays of Au nanoparticles with controlled size and spacing on silicon wafer substrates; following which the nanoparticles are grown to form different shapes utilizing a seed-mediated growth method. Au and Pd growth on Au seeds are achieved utilizing this approach. The grown particle size, shape, and interparticle distance can be tuned by varying the growth solution concentration, growth time, and using different Au seed arrays. These grown arrays of metal nanoparticles are excellent substrates for surface enhanced Raman spectroscopy (SERS). 1,4-phenylene diisocyanide (PDI) is used as a probe molecule to illustrate the application of these grown particle arrays in SERS. Poster 2 O2 Reduction on Uniform Pt Nanoparticle Array Electrodes, Hongzhou Yang, Sachin Kumar and Shouzhong Zou*, Miami University Center for Nanotechnology, Department of Chemistry & Biochemistry, Oxford, Ohio Oxygen reduction reaction (ORR) is one of the most extensively studied electrochemical reactions due to its important role in fuel cells. A long-standing debate on the ORR is whether the reaction kinetics depends on the particle size. In the past decades, controversial observations have been reported by different research groups. One conceivable reason for the disagreement between different authors is the lack of a good control of particle size and interparticle distance. Recent advancement in the nanoparticle synthesis and fabrication offers new opportunities for exploring the particle size and other structural dependence of reactivity. In the present work, uniform arrays of Pt nanoparticles with controlled size and interparticle distance supported on glassy carbon electrodes were formed by using polystyrene-poly(2-vinylpyridine) diblock copolymers as the template. Electroreducion of O2 on these Pt nanoparticle arrays was studied using rotating disk (RDE) and rotating ring-disk electrode (RRDE) voltammetry. The obtained results indicated that the specific activity of O2 reduction increased with increasing particle size and the extent of H2O2 formation increases as the particle size decreases. Poster 3 Effect of Dye Adsorption on Nanostructured TiO2 and ZnO based Dye Sensitized Solar Cells, Jie Pan and Lei L. Kerr, Miami University Center for Nanotechnology, Department of Paper and Chemical Engineering, Oxford, Ohio Very recently, there is a growing interest in using ZnO as an alternative electrode. However, the efficiency of ZnO based-DSSC is much lower than that based on TiO2. The interface between the ZnO/dye directly impacts the DSSC performance. Nanostructured porous ZnO film was developed by a simple chemical solution process. Nanostructured TiO2 was grown by dip coating. The films of ZnO and TiO2 were controlled at similar thickness. Adsorption studies were conducted at 25ºC and 40ºC. The results showed that the Both TiO2 and ZnO based solar cell performance were significantly influenced by the dye adsorption temperatures. At higher adsorption temperature, the overall cell efficiency of ZnO based solar cells is improved by 30% (from 0.552% to 0.736%). Moreover, the problem of the dye aggregation on the ZnO surface was reduced at higher adsorption temperatures. The adsorption temperature has the adverse effect on TiO2 based solar cell. At higher temperature, the overall cell efficiency of TiO2 solar cell is decreased from 0.856% to 0.602%. The adsorption mechanism and the opposite effect of dye adsorption temperature on TiO2 and ZnO electrode is investigation. Poster 4 CO and methanol electrooxidation on uniform Au nanoparticle arrays in alkaline media – Role of particle size and interparticle distance, Sachin Kumar and Shouzhong Zou* Miami University Center for Nanotechnology, Department of Chemistry and Biochemistry, Oxford, Ohio In fuel cell research, the role of catalyst particle structure, including size, surface atomic arrangement, and composition towards catalyst performance have eluded researchers for a long time. A common limitation in the previous studies of nanoparticle electrocatalysis is the poor control over particle size and distribution. Particle aggregation along with other issues such as the presence of surfactant complicates the experimental results. CO and methanol electrooxidation are two most studied reactions in nanoparticle catalysis. This is primarily due to their importance in fuel cell development. Typically, Pt and Pt-based alloy particles are used for methanol oxidation. CO poisoning effect along with the high cost of Pt has encouraged researchers to find alternative catalyst materials. Au is one of such alternative materials. Although Au is traditionally considered as a poor catalyst for methanol oxidation, it has been demonstrated by various researchers that after undergoing activation steps, Au can possess unusually high catalytic activity. Another advantage is that during methanol oxidation, in contrast to the reaction on Pt, CO is not formed on Au. In addition, in gas phase, supported Au nanoparticles show unexpectedly high catalytic activity towards CO oxidation and the reactivity is size dependent. Corresponding reaction in electrochemical environment has not been systematically studied. In this presentation we will demonstrate a simple route to synthesize arrays of Au nanoparticles where the size and interparticle distance between nanoparticles are well controlled. CO and methanol electrooxidation in alkaline media on these Au nanoparticles will be used to explicate the relationship between particle size, interparticle spacing and reactivity. Comparison between gas phase and electrochemical CO oxidation will be discussed as well. Poster 5 Polymer thin film Modeling with Silica Substrate in presence of Carbon Dioxide, Anand Srivastava, Coleman Alleman, Somnath Ghosh, Jintao Yang, L J Lee Department of Mechanical Engineering, The Ohio State University, Columbus, Ohio. The classical processing and fabrication technologies
that produce stable macro and micro level polymer structures
cannot be used for fabrication of nanostructures because of
the length scale dependence of critical properties like Glass
Transition Temperature (Tg). Novel methods of fabricating polymers
nanostructures without introducing either organic solvents or
higher processing temperatures are being explored. One of the
methods is the use of sub critical CO2 as an intermediate processing
agent in the Polymer. In presence of CO2, there is Tg depression,
reduced viscosity and reduced interfacial tension, all of which
felicitate processing. However, because of the absence of any
understanding of the underlying molecular level mechanisms involved,
fabrication of stable structure is still questionable. Poster 6 Low-Cost Nanocomposite Tooling for Agile Manufacturing,
Richard Garozzo, Tom Glenchur, Derek Johnson, Ken Han, University
of Dayton Research Institute, Dayton, Ohio Poster 7 This poster will highlight three areas of achievement and capability relating to the production of polyimide materials with enhanced properties via addition of carbon nanofibers. The first area involves organic functionalization of carbon nanofibers for improved compatibility with polyimide resin systems. The second area is production of thermoplastic polyimide films with well dispersed nanofibers for enhanced mechanical and electrical properties. The third area is addition of carbon nanofibers to thermosetting polyimide resins for improved mechanical and thermooxidative stability. The poster will highlight not only the material properties but the scaleable processing techniques used to produce these materials. Poster 8 Carbon Nano Fiber (CNF) Modified Thermoplastic Polymer Process and Property Study, Jared Stonecash, James Hartings, University of Dayton Research Institute, Multiscale Composites and Polymers Division, Dayton, Ohio Abstract: Several thermoplastic + carbon nanofiber (CNF) nanocomposites were prepared by melt compounding and extrusion. These materials were then injection molded into tensile bar test specimens (ASTM D638) for material property evaluation. Injection molding process conditions were varied for the baseline thermoplastic polymers as well as for the polymer nanocomposites to determine molding condition affects on final part properties. CNF concentration was varied by diluting the base nanocomposite with more polymer to yield the desired nanofiber loading level. All of the final parts were evaluated for tensile properties, CNF dispersion and electrical properties to provide structure-property relationships for this new class of multi-functional materials. Poster 9 Nanophotonic Device Engineering, Scott A. Masturzo1, Joseph T. Boyd1, Howard E. Jackson2, Jan M. Yarrison-Rice3, Robert L. Ewing4, 1 Department of Electrical & Computer Engineering, University of Cincinnati, 2 Department of Physics, University of Cincinnati, 3 Department of Physics, Miami University, 4 Air Force Research Laboratories, WPAFB Design, fabrication, and characterization of nanophotonic devices including grating couplers, planar solid immersion lenses, and photonic crystals is presented. Integration of optically active materials with silicon-on-insulator photonic crystals for optically tunable devices is discussed.
Poster 11 Substrate Preparation by Magnetron Sputtering for Chemical Vapor Deposition Growth of Long Carbon Nanotube Arrays, Pravahan Salunkea, Sergei Yarmolenkoc, Sudhir Nerallac, Svetlana Fialkovac , Jaganathan Sankarc, Kyle Fischbacha, Ge Lia, Chaminda Jayasinghea, Wondong Choa, Emily Heada, Yeo-Heung Yunb, Mark Schulzb and Vesselin Shanova*, aDepartment of Chemical and Materials Engineering, University of Cincinnati, Cincinnati, Ohio, bDepartment of Mechanical, Industrial and Nuclear Engineering, University of Cincinnati, Cincinnati, Ohio, c Department of Mechanical and Chemical Engineering, North Carolina Agricultural and Technological State University, Greensboro, NC In this study we explored the use of magnetron sputtering as an alternative to e-beam deposition for preparation of the alumina intermediate layer and of the metal catalyst on an oxidized Si wafer. This approach offers large area deposition of the layered substrate which is promising for scaling up the process. The effects of the substrate design on the growth of long multi-wall carbon nanotube (MWCNT) arrays by CVD (Chemical Vapor Deposition) were also explored. The CNT synthesis was carried on in a hydrogen/ethylene/water/argon environment at 750 °C for different periods of deposition time. Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Thermal Gravimetric Analysis (TGA) and Transmission Electron Microscopy (TEM) were employed to characterize the substrates and the CNT arrays. The study showed that for specific processing conditions the length of highly oriented CNTs strongly depends on the thickness of Al2O3 intermediate layer and on the catalyst film. The obtained results confirm that magnetron sputtering can be successfully employed as a tool for substrate preparation which was used to grow up to 10 mm long CNT arrays with high purity. The aligned nanotubes do not suffer from limitations typical for powdered (spaghetti type nanotubes) which opens up possibilities for new applications. Poster 12 Carbon nanoadditives to enhance latent energy storage of phase change materials, Shadab Shaikh, Khalid Lafdi, Kevin Hallinan. Mechanical Engineering, University of Dayton, Dayton, Ohio The present work focus on analyzing the energy storage capacity of a PCM based nanocomposites. It is perceived that by the intimate inclusion of carbon nanotubes (CNT) in the PCMs their thermal properties can be changed. For a matrix with nano-scale CNT the surface to volume ratio is very high and consequently the molecular interaction between the nanotube surface and PCM can change the heat of fusion and melting point of the original PCM. By optimizing the amount of CNT inside the PCM, the properties of the PCM can be altered to improve their thermal performance based on a specific application. Poster 13 An assay for metallic/semiconducting carbon nanotube contents in mixtures, Wei Lu, Yao Xiong, and Liwei Chen, Ohio University, Nanoscale and Quantum Phenomena Institute (NQPI), Athens, Ohio An assay for metallic/semiconducting carbon nanotube contents in mixtures, Ohio University, Nanoscale and Quantum Phenomena Institute (NQPI), As prepared single-walled carbon nanotube samples are mixture of metallic and semiconducting species. Although electric transport measurements and resonance Raman spectroscopy can give some information about the metallic or semiconducting nature of the tubes, a quantitative assay for the content of these two categories is lacking. Here we report a scanning force microscopy based assay. Poster 14 Smart Nanocomposites for Industrial Health Monitoring, Gunjan Maheshwari1, Wondong Cho2, Jandro Abot3, Nilanjan Mallik1, Surya Narayanan Sundaramurthy1, Emily Head2, Mitul Dadhania1, Weifeng Li1, Vesselin Shanov2, Chaminda Jayasinghe2, Pravahan Salunke2, Lucy Lee2, Douglas Hurd1, YeoHeung Yun1, Sergey Yarmolenko4, Jag Sankar4, Mark J. Schulz1, 1-University of Cincinnati, Mechanical Engineering, Cincinnati, OH, 2-University of Cincinnati, Chemical and Materials Engineering, Cincinnati, OH, 3-University of Cincinnati, Aerospace Engineering, Cincinnati, OH, 4-Department of Chemical and Mechanical Engineering, Center for Advanced Materials and Smart Structures, North Carolina A&T State University, Greensboro, NC There is a need for new smart materials for use in large industrial health monitoring applications. This paper explores the use of Carbon Nanotubes (CNT) and Carbon Nanosphere Chains (CNSC) to develop nanocomposite smart materials having electrochemical impedance, piezoresistive, and magnetic properties for sensing. These responsive nanocomposites exhibit a change in electrical conductivity due to strain that can be used for detection of structural damage and abnormalities. Along with excellent mechanical, thermal, and electrical properties, CNSC have shown weak magnetic properties obtained by post processing the material. This novel material might be used to replace iron thereby reducing sensor weight and cost, which can be crucial for industrial applications. Nanocomposites based on host materials like epoxy, elastomers, cement, and ice have shown a change in electrical properties when subjected to stress. Distributed sensors based on “spray-on nanocomposites” on complex structures change electrical impedance when subjected to external loading. Fabrication, characterization and testing of carbon nanocomposite materials will be discussed in the paper. Electrochemical Impedance Spectroscopy (EIS) and piezoresistivity testing will be discussed to characterize the electrical properties of the nanocomposite. Since the nanocomposite has piezoresistivity and electrochemical properties, it can monitor the health of a structure and detect changes due to deterioration of large complex structures. Also, a novel application of CNT arrays is improving the interlaminar shear strength and enhancing the transverse elastic modulus of aligned fiber composites. This can be crucial for the automotive and aerospace industries because there is a need to improve the transverse properties and toughness of lightweight fiber composites. Poster 15 CAE Applications in Product and Process Developments
of Nano-Composites, Ken Han and Brian Rice, Multiple Scale Composite
& Polymer Division, UDRI, Dayton, Ohio A CNT hierarchical reinforcement approach for superior matrix-dominated properties in fiber reinforced polymeric composites. Mandar Kulkarni1, Gunjan Maheshwari2 , D. Qian2 ,J. L. Abot1, 1Department of Aerospace Engineering & Engineering Mechanics, University of Cincinnati, 745 Baldwin Hall, Cincinnati, OH, 2 Department of Mechanical Engineering, University of Cincinnati, Cincinnati, OH Fiber composite materials are ideal engineered materials to carry loads and stresses in the fiber direction due to their high in-plane specific mechanical properties. However, premature failure due to low transverse ultimate material composite properties constitutes a fundamental weakness of composites. A solution to this problem is being addressed through the creation of a nanoreinforced composite material where carbon nanotubes are grown in the surface of the fiber filaments to increase the matrix-dominated properties. The carbon nanotubes increase the effective diameter of the fiber and provide a much larger interface area for the polymeric matrix to wet the fiber.. These nanoreinforced composite materials are presently being fabricated and characterized under quasi-static mechanical loading in the transverse direction to the fiber. A study is now being carried out to numerically predict the elastic properties of these nanoreinforced composites. A fully three-dimensional (3D) Finite Element (FEA) is being developed considering perfect bonding between the phases of the composites. Preliminary studies were conducted on a representative volume element of a non-reinforced composite and the results were correlated with micromechanical models. The numerical results from this study will be correlated with those of the experiments for the nanoreinforced polymeric composites. These composites could prove critical for many automotive and aerospace industries where there is a need to improve the transverse properties and toughness of lightweight fiber composites. Poster 17 Electrodeposited Perpendicularly Oriented Mesoporous Materials, Aleksey N Pisarenko, Wolfgang U. Spendel, Richard T. Taylor, Jordan D. Brown, James.A. Cox, and Gilbert E. Pacey, Miami University Center for Nanotechnology, Department of Chemistry and Biochemistry, Oxford, Ohio Mesostructured supported films have been synthesized to produce new electrodeposited perpendicularly oriented mesoporous materials (EPOM’s). The principle demonstrated here is electrochemically induced self-assembly of CTAB (cetyl trimethylammonium bromide) surfactant at the solid-liquid interface and electrochemical catalysis method to produce sol-gel EPOM. A substituted coumarin 4 molecule was incorporated into the sol gel material and was used to study the various characteristics of the EPOM. Poster 18 Synthesis of ZnO Nanoparticles By Microwave Radiation, Sasha A. Ivanov, Aleksey N Pisarenko, Wolfgang U. Spendel, and Gilbert E Pacey, Miami University Center for Nanotechnology, Department of Chemistry and Biochemistry, Oxford, Ohio Zinc oxide (ZnO) nanoparticles were synthesized in aqueous / glycerin solutions using microwave radiation. The reported method is faster, less costly, and comparatively selective as compared to hotplate or oven synthesis methods. Different sizes and shapes are controlled by varying the water to glycerin ratio in sample solutions. Spheres, rods, and cones are obtained. Particles sizes of 25-500 nm are produced. This allows us to tune optical properties of the nanoparticles. Poster 19 Dynamic Covalent Assembly of 2D Organic Nanostructures, C. Scott Hartley,1,2 Erin L. Elliott,2 and Jeffrey S. Moore2 1Miami University Center for Nanotechnology, Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 2Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois The construction of atomically-precise organic nanostructures represents a current challenge for organic materials synthesis. Dynamic covalent chemistry has established itself as an attractive route to the self-assembly of nanoscale organic compounds, allowing the formation of multiple covalent bonds in a single step in high yield. Here we demonstrate that imine formation/metathesis can be used to crosslink m-phenylene ethynylene oligomers to give two dimensional shape-persistent nanostructures. The resulting structures are simple [n]-rung molecular ladders with dimensions of up to ~1.6 × 6.2 nm (n = 6). These materials represent the first step in the synthesis of larger grids with potential use as high precision nanofiltration membranes or “smart matrix” grids to position units for solar energy harvesting. We also demonstrate that the directionality of the imine bond can be used to program covalent self-assembly, much in the same way that the directionality of the hydrogen bond is used to direct the assembly of non-covalent structures. Specifically, we have prepared a series of unsymmetrical shape-persistent macrocycles with a variety of side-chain substitution patterns. Poster 20 EMI Shielding Properties of Exfoliated Graphite Based Nanocomposites, Matt Boehle, Elizabeth Zinsser, Khalid Lafdi, Peter Collins, 1. University of Dayton, 300 College Park Dayton Ohio, 2. Air Force Institute of Technology, 2950 Hobson Way Wright-Patterson AFB, Ohio The increasing density of electronic devices in industrial and military applications has lead to a need for enhanced electromagnetic shielding properties. Plastics have also become a major component in most electronic devices. Polymer composite shielding materials utilizing carbon nanotechnology merge these requirements into a device with reduced cost, higher performance and lower weight. In this study, the relationship between EMI shielding effectiveness and resistivity of epoxy composites was examined. Test specimens were prepared with varying concentrations and sizes of exfoliated graphite used as an additive. Exfoliated graphite is an ideal choice as it possesses high conductivity, light weight and low cost. After testing the composite panels, a strong correlation between electrical properties and EMI shielding was found. The end goal of this work is to characterize the EMI shielding performance of carbon nanocomposites in order to design a material which can be optimized for a given application. Poster 21 SiO2 Thin Film Deposition Techniques and Low Index SiO2 Thin Film, Mengshu Pan, Andrew Sarangan University of Dayton Three common SiO2 thin film deposition techniques are presented here, which are Radio Frequency Sputtering, Electron-Beam Evaporation and Plasma Enhanced Chemical Vapor Deposition. The fabrication of ultra-low index nano-porous glass film using oblique angled e-beam evaporation and the experimental results are also presented. Poster 22 Nanostructured Carbon Containing Nitrogen as Cathode Catalysts in the PEM Fuel Cells, Elizabeth J. Biddinger, Paul H. Matter, Dieter von Deak, Umit S. Ozkan, Chemical and Biomolecular Engineering, The Ohio State University, Columbus, Ohio Less expensive nitrogen containing carbon nanostructured (CNx) catalysts have been studied as an alternative to the current oxygen reduction reaction (ORR) Pt catalysts for the cathode catalyst of PEM and Direct Methanol Fuel Cells. These CNx catalysts have been shown to be active for ORR in acidic media. The nature of the active site for nitrogen-carbon ORR catalysts has been debated in the literature. Previous studies at Ohio State have revealed that a transition metal is not required on the CNx catalyst for it to reduce oxygen. Activity increased with graphitic edge plane exposure and pyridinic-Nitrogen content (found on the edge plane) determined by X-ray photoelectron spectroscopy (XPS). Nano-structure morphology appeared to affected ORR activity and selectivity. These CNx catalysts have been extensively characterized and tested for activity and selectivity by the rotating ring disk method (RRDE). Poster 23 There has been recent and growing interest in graphene, a two-dimensional sheet of benzenoid carbon atoms (the basic unit of graphite), for use in nanoscale electronics and other areas (e.g., hydrogen storage, organic magnetism). Here we discuss our efforts toward the bottom-up synthesis of one-dimensional (board-like) graphene oligomers. Our strategy is to synthesize an o-phenylene oligomer, which will be planarized by oxidative cyclodehydrogenation (the Scholl reaction). We expect these materials to compliment the behavior of the existing graphene nanostructures prepared by organic synthesis (e.g., hexabenzocoronenes). Specifically, we believe they will be predisposed to lamellar (as opposed to columnar) self-assembly, and will better maintain solubility as their size is increased. Poster 24 Novel Materials Based on Tubular Discotic Liquid
Crystals, Amanda E. Ponsot, Katherine M. Digianantonio, and
C. Scott Hartley*, Miami University Center for Nanotechnology,
Department of Chemistry and Biochemistry, Miami University,
Oxford, Ohio Poster 25 Poster 26 Growth of Carbon Nanotubes on Porous Microcellular Carbon Substrates I.T. Barney, A.G. Jackson, and S.M. Mukhopadhyay Department of Mechanical and Materials Engineering, Wright State University This project focuses on the growth of carbon nanotubes (CNTs) over larger engineering structures, including microcellular porous material. The goal is to create multi-scale materials with significantly increased surface area for advanced thermal, catalytic and electrochemical applications. Nanotubes have been fabricated on various graphitic substrates (microcellular foams, fibers, and flat model surfaces ) using chemical vapor deposition (CVD). Structure and morphology of CNT growth has been characterized using Field Emission Scanning Electron Microscopy (FE-SEM) and analyses of chemical states have been preformed using x-ray photoelectron spectroscopy (XPS) It is seen that a plasma enhanced nano-coating on the uneven surface significantly enhances its catalytic activity, and improves CNT growth. Other factors influencing growth kinetics are gas flow and pore geometry. BET surface area analysis and thermal transport measurements have been performed to understand structure- property relationships. These results will be presented in light of understanding and controlling growth mechanisms for future applications. Poster 27 Two Photon absoption and nonlinear refraction in PTCDA films, *A.M. Ajward, V.R. Gangilenka, #H. Schmitzer, *H.P. Wagner, *Department of Physics, University of Cincinnati, Ohio, #Department of Physics, Xavier University, Cincinnati, Ohio The two-photon absorption coefficient of a polycrystalline PTCDA (perylene-3,4,9,10-tetracarboxylic-3,4,9,10-dianhydride) thin film was measured at 880 nm using the z-scan technique. The 2 µm thick PTCDA film was grown by organic molecular beam deposition (OMBD) on Pyrex. For the z-scan measurements ~1 ps pulses were focused onto the thin film using a microscope objective lens (100x) of numerical aperture 0.55 and a beam waist of 1 µm. The films have been moved by a translation stage with a travel range of 100 µm and with a step size of 0.5 µm. The two-photon absorption coefficient of PTCDA obtained from a fit with open aperture measurements at different intensities results to ~20 cm GW-1 and the nonlinear refraction coefficient obtained from a fit to closed aperture measurements results to ~-1.4x10-12 cm2/W. The z-scan measurements demonstrate that crystalline PTCDA films possess strong nonlinear optical properties that might be utilized for optical applications. Poster 28 Effect of Catalysts, Contaminants and Surface Area on Toxicity of Carbon Bases Nanomaterials, K. Lafdi, C. Grabinski, M. Gamble and P. Tsonis, Center for Tissue Regeneration and Engineering at Dayton, University of Dayton, 300 College Park, Dayton, Ohio. Previous studies have shown that the presence of metal impurities plays an important role in the toxicity of carbon nanotubes (CNT). Specifically, the metal impurity content correlated to the level of oxidative stress in the cells, marked by the production of reactive oxygen species (ROS). However, the viability of the cells, measured by their mitochondrial function, did not correlate directly with the metal impurity content in CNT, so there must be additional factors that affect the toxicity of carbon-based nanomaterials. Many studies have suggested that high surface area per mass may play a role in nanomaterial toxicity. Therefore, further studies were carried out to test the effect of surface area on cell viability and oxidative stress in vitro. Results showed that CNT with low impurities and low surface area did not significantly reduce cell viability or induce oxidative stress in cells. However, nanographite, induced the production of ROS nearly 10 times greater than that induced by CNT with high impurities. Because nanographite lacks impurities, this effect must be due to the exceptionally high surface area. To compliment these results, the relative toxicity of metal catalysts commonly used in the synthesis of CNT was investigated, including aluminum oxide coated and uncoated iron, nickel, and cobalt. It was found that aluminum oxide-coated nanoparticles produced less toxicity than those that were not coated. The results of these studies reveal that carbon-based nanomaterial toxicity is a function of both impurity content and surface area, and that toxicity of metal catalysts is reduced with the addition of an aluminum oxide coating. Poster 29 Thermo-optical Properties and Characterization of Heat Generation of Single Gold Nanoparticles Embedded in Ice, Thomas, A. C.1, Richardson, H. H.1, Carlson, M. C.1, and Govorov, A. O.2, 1Ohio University, Chemistry and Biochemistry, Athens, Ohio, 2Ohio University, Physics and Astronomy, Athens, Ohio We have previously investigated the thermo-optical properties of gold nanoparticles (Au NPs) embedded in an ice matrix.1 Resonant laser light of relatively weak intensity is able to melt ice with embedded Au NPs, whereas even a very intense laser beam does not melt ice alone. We have also theoretically determined that the local temperature in and around a NP complex is dependent on its geometry and large scattering in melting power is observed for aggregated complexes.2 By immobilizing the NPs on a glass surface, we are able to characterize them by atomic force microscopy (AFM) and single particle spectroscopy. Using both techniques, we are able to determine the heat generation of single NPs embedded in an ice matrix as a function of laser intensity and matrix temperature. 1 Richardson, H. H.; Hickman, Z. N.; Govorov,
A. O.; Thomas, A. C.; Zhang, W.; Kordesch, M. E., Thermooptical
properties of gold nanoparticles embedded in ice: Characterization
of heat generation and melting. Nano Letters 2006, 6, 783-788. Poster 30 Single CdS Nanosheets: Spatially-resolved Photoluminescence
Mapping, M. Fickenscher, T. B. Hoang, L. V. Titova, A. Mishra,
L. M. Smith, H. E. Jackson, Department of Physics, University
of Cincinnati, Cincinnati, OH 45221, J. M. Yarrison-Rice, Physics
Department, Miami University, Oxford, OH 45056, H. Rho, K. -Y.
Lee Results of spatially-resolved low temperature photoluminescence of single 5 micron wide, 30 micron long and 50 nm thick CdS nanosheets are presented. The sheets, grown by pulsed laser deposition using vapor-phase transport, are uniform in size and shape and exhibit a hexagonal wurtzite structure. The orientation of the c-axis determined by PL polarization analysis and HR TEM varies from sheet to sheet. A method for determining the c-axis direction from the polarized PL is demonstrated. The spatially-resolved PL reveals spectral variation across the sheet, with A-like excitons at the edges showing a spectral peak at 2.547eV, and B like excitons at the center showing a peak at 2.563eV. Exciton lifetimes of ~200 ps are observed, which are significantly longer than CdS nanowires of identical diameter, but shorter than measured in bulk CdS. Support provided by NSF (#0701703), Korea Research Foundation and KIST. Poster 31 Synthesis and Chemistry of Size-Constrained
Cadmium Sulfide Quantum Dots in Microporous Materials, Jeremy
White, Prabir K. Dutta, Department of Chemistry, The Ohio State
University, 120 W 18th Avenue, Columbus, Ohio Polymer-fullerene bulk heterojunction photovoltaic (PV) devices are of tremendous interest for their potential societal benefits and the opportunity for relatively low cost production on flexible substrates. We will discuss the interface engineering, the low-bandgap absorber toward for spectral expansion, and hermetic packaging for highly efficient polymer-fullerene bulk heterojunction PV devices. Poster 33 e-mail sent Ceramic Nano-Structures without Lithography: Platforms for Chemical Sensing and Catalysis, B. Dinan, S. Yoo, C. Carney, M. Rauscher, H. Lee, S. Dregia and S. Akbar, Material Science, The Ohio State University, Columbus, Ohio Due to their enhanced properties nanostructures have been widely researched. One way to produce nanostructures is by a gas phase reaction brought about by a thermal treatment process. Using this method we have developed several different ceramic nanostructures from a wide range of materials including SnO2, TiO2, Ti, and Gd-doped CeO2. Some potential applications for these materials include platforms for chemical sensing, catalysis, photo-catalysis, bio-medical, and nano-fluidics. Poster 34 Impact of Near-Surface Native Point Defects,
Chemical Reactions and Surface Morphology on ZnO Interfaces,
D. Doutt,1 M. Kramer,1 D. Tayim,2 C. Zgrabik,1 Z.Q.Fang,3 D.C.
Look,3 G. Cantwell,4 J. Zhang,4 J.J. Song,4 H.L. Mosbacker,1
L.J. Brillson1,5 1Department of Physics, The Ohio State University,
Columbus, Ohio 2Columbus School for Girls, Bexley, Ohio, 3Z.Q.Fang
and D.C. Look, Wright State University, Dayton, OH 45433, 4ZN
Technology, Inc., La Brea, California, 5Dept. of Electrical
& Computer Engineering, Ohio State University, Columbus,
Ohio Poster 35 Phonon-assisted charge hopping and its role in odor recognition models, Edson Vernek and Sergio Ulloa, Department of Physics and Astronomy, and Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio How humans recognize odors is a very interesting subject. Although attempts to explain how we recognize several odors from different molecules at different concentrations have been published, the models are still unable to fully explain the molecular selectivity of odorants and other characteristics of the olfactory process. One recent attractive model was proposed by Luca Turin in the last decade [1]. Turin's ideas were based on exploring the role of quantum mechanical vibrations (phonons) in the activation mechanism that triggers odorant detection. One of the advantages of his model compared to the “/lock and key”/ model [2] is that he was able to explain why different molecules may smell alike while other very similar molecules smell different. Turin suggested that the size and shape argument implied in the “/lock and key” /mechanism may be important but it is not enough to explain odor recognition. Recently a Hamiltonian model was proposed by Brookes et al. [3], which took steps to quantitatively confirm the viability of Turin's ideas. The model is based on a two level system (/donor/ and /acceptor/ levels) with a /local/ electron-phonon interaction, which produces inelastic (phonon-assisted) tunneling between the /donor/ and /acceptor/ levels. Realistic systems, however, may include not only local but /non-local/ electron-phonon interactions, where electron can relax from the /donor/ to the /acceptor/ level by emitting a phonon. We propose a Hamiltonian which includes this mechanism and study the consequences of their presence for the Turin's mechanism. Preliminary results show that for almost the entire range of /non-local/ electron-phonon coupling the model still contains the proper conditions of validity of Turin's model. However, we find that for a narrow range of coupling values, odor recognition is not possible and the model breaks down. References:
Cavity Resonances of Metal-Dielectric-Metal Nanoantennas, Bhuwan P. Joshi and Qi-Huo Wei, Liquid Crystal Institute, Kent State University, Kent, Ohio We numerically study the optical properties of nanaoantennas consisting of two metal nanorods stacked vertically with a dielectric disk spacer. In addition to antenna resonances, these new nanoantennas show interesting cavity resonance behaviors when the spacer thickness is below 5nm and the diameter of the dielectric disk is smaller than the diameter of the metal rods. The antenna resonance generates a peak in far-field scattering spectra, while the cavity resonances generate multiple dips in the scattering spectra. The cavity and antenna resonant frequencies are widely tunable through varying the size of the dielectric disk. Cavity resonances result strong local field enhancements inside the nanocavity, and the enhancement factors are much higher than those resulting from only antenna resonances. This new nanoantenna promises applications in single molecule surface enhanced Raman spectroscopy (SERS) due to its high local field enhancements and large scale manufacturability. Poster 37 Ordered Manganese Atom Structure on Semiconducting
Wurtzite Gallium Nitride, Abhijit Chinchore, Kangkang Wang,
Wenzhi Lin, Jeonghim Pak, Arthur Smith, Nanoscale and Quantum
Phenomena Institute ; Physics and Astronomy Department. An important technological challenge of nanoscience
is to bring together magnetism and electronics under a single
material system or combination. This can lead to novel data
storage and device functionality based on use of the electron's
spin degree of freedom. Efforts to introduce transition metal
atoms into III-V semiconductor host materials have been difficult,
due particularly to solubility issues. Still, there is much
interest in achieving transition metal atoms dispersed uniformly
in gallium nitride, due to the possibility of forming room-temperature
operating dilute magnetic semiconductors.[1] In this project,
we investigate the formation of an ordered array of manganese
atoms on the gallium nitride surface. The manganese atom layer
is formed by evaporation of Mn onto the prepared GaN substrate
surface in sub-monolayer doses. High energy electron diffraction
is used to monitor the evolution of the surface in real time.
After depositing less than 1 monolayer Mn, we observe the formation
of a highly ordered surface consisting of Mn atoms spaced at
equal nano-scale intervals. Such a well- ordered Mn structure
may have interesting nanoscale magnetic properties which can
be studied using surface-sensitive magnetic probes. The project
is supported by DOE and NSF. Poster 38 Polyimide Nanocomposites with Tunable Coefficient
of Thermal Expansion, Gayathri R Sharma1, Maria R Coleman1 and
Cora Lind2 , 1 Department of Chemical and Environmental Engineering,
The University of Toledo, Ohio, 2 Department of Chemistry, The
University of Toledo, Ohio Imaging charge transfer molecular orbitals, U.G.E. Perera1, F. Jäckel1, 2, V. Iancu1, K.-F. Braun1, N. Koch2, J. P. Rabe2, S.-W. Hla1, 1Ohio University, Physics & Astronomy Department, Athens, Ohio, 2Humboldt-Universität zu Berlin, Institut f. Physik, Newtonstraße 15, 12489 Berlin, Germany. A low temperature scanning tunneling microscope (STM) and spectroscopy (STS) study under ultra-high vacuum conditions of organic charge transfer complexes (CTCs) is presented. The complexes are formed by self assembly from the electron donor a- sexithiophene (6T) and the electron acceptor tetrafluro-tetracyano-quinodimethane (F4TCNQ) on Au(111) surface. The formation of new hybrid molecular orbitals in CTCs are indicated by differential conductance spectra (dI/dV). The highest occupied molecular orbital of the CTC is mainly located on the electron accepting F4TCNQ and the lowest unoccupied molecular orbital is located on the electron donating 6T. Further, voltage dependent STM images and the dI/dV maps of CTCs reveal the intensity changes of F4TCNQ locations based on bias voltage. This work is financially supported by the US Department of Energy Basic Energy Sciences grant no. DE-FG02-02ER46012 and OU-BNNT. Poster 40 Well Width Dependence of the Phase Coherent
Photorefractive Effect in ZnSe Quantum Wells, Amin Kabir1, Alexander
Pawlis2, Marina Panfilova2, Klaus Lischka2 and Hans-Peter Wagner1,
1 Department of Physics, University of Cincinnati Cincinnati,
Ohio, 2 Department of Physics, University of Paderborn, Warburger
Str. 100, 33098 Paderborn, Germany Poster 41 Optical coherence imaging using novel phase coherent photorefractive ZnSe quantum wells, A. Kabir, M. Ajward, S. Tripathy, H. P. Wagner, Department of Physics, University of Cincinnati, Cincinnati, Ohio We have performed depth-resolved optical coherence imaging (OCI) of both stationary and moving objects using the exciton resonant phase coherent photorefractive (PCP) effect in ZnSe quantum wells (QWs). PCP QWs operate without electrical contacts thus avoiding elaborate sample processing and avoiding sample destruction due to Joule heating. In addition, the PCP effect exploits the coherence of excitons in OCI experiments thus enabling 3D images of reflecting objects with a depth resolution of ~15 ?m using 90 fs pulses. Due to the high diffraction efficiency of ? = 5x10-4 in our PCP ZnSe QWs we are able to record still images at very low intensities (~ 500 µW/cm-2). The OCI movies of moving objects were recorded using a camcorder with frame rates of 60 and 180 Hz. The shortest possible time resolution in these experiments is determined by the decay time of the PCP electron grating being in the ~10 ?s range. Poster 42 Synthesis and Characterization of Metal-Oxide-Metal
Heterojunction Nanowires, Oxide nanowires (nanoribbons, nanobelts, or nanorods) are being used increasingly as 1-dimensional (1-D) building blocks in “bottom up” multifunctional nanoelectronics, taking advantage of the myriad size-dependent functional properties of oxides. In this context, metal—oxide—metal (MOM) heterojunction nanowires, where a nanoscale segment of a functional oxide is sandwiched axially between two noble-metal nanowires, are likely to have some distinct advantages over all-oxide nanowires (where the entire nanowire is an oxide), including definition of the functional segment of oxide and “end-on” contacts. In order to study piezoelectric and ferroelectric properties of nanoscale oxides, a novel synthesis method is developed to make MOM nanowires in the Au-BaTiO3-Au system. The synthesis method is described in detail along with characterization results of the MOM nanowire structure. Additionally, an approach for fabricating electronic devices incorporating these nanowires is presented. Poster 43 e-mail sent Precipitation anneals in the PbTe-PbS system*, Christopher M. Jaworski1, Joseph P. Heremans1,2 Steven N. Girard3, Mercouri Kanatzidis3, 1 Department of Mechanical Engineering, The Ohio State University, 2 Department of Physics, The Ohio State University, 3 Department of Chemistry, Northwestern University Bulk samples of (Pb1-xSnxTe)1-y (PbS)y have been prepared in the range 4%<y<30%1. There is a miscibility gap in the pseudo-binary PbTe/PbS phase diagram that enables the precipitation of a PbS-rich phase in a PbTe-rich matrix. To that effect, the samples were compounded in the liquidus, and then quenched, resulting in a supersaturated solution. Conditions for precipitation anneals were then developed, and samples with nano-precipitates of a PbS-rich phase in a PbTe-rich parent phase have been obtained, as evidenced by X-ray diffractions. This technique, previously applied to Pb-rich PbTe2, is aimed at creating a bulk material containing a substantial fraction of nanometer-sized particles in order to mimic the morphology of quantum-dot superlattices that reached very high values of the thermoelectric figure of merit.3 This material’s notably low thermal conductivity will not be discussed here. Galvanomagnetic and thermomagnetic data will be presented with the aim of identifying the electronic properties of the materials. [1] 1. Kanatzidis, et. al. J. AM. CHEM. SOC.
2007, 129, 9780-9788. [2] J. P. Heremans, C. M. Thrush and D.T.
Morelli, Thermopower enhancement in PbTe with b precipitates,
J.Appl. Phys. 98 063703 (2005 [3]T. C. Harman, M. P. Walsh,
B. E.LaForge, and G. W. Turner, J. Electron. Mater. 34, L19
(2005). Poster 44 Novel Organic-Inorganic Hybrid Solar Cells Based on Titania Nanotube Arrays and Metalloorganic/Polymer Blends, Tengfei Jiang and Nitin P. Padture, Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio Fabrication, structure, properties, and performance of novel organic-inorganic hybrid solar cells based on titania nanotube arrays and metallo-organic/polymer blends are presented. Ordered arrays of amorphous nanotubes are formed on indium-tin-oxide (ITO)-coated glass substrates using the anodization method, and they are subsequently crystallized to rutile titania. The nanotube dimensions are carefully tuned considering the exciton diffusion lengths, for improved efficiency. Hole-conducting polymers are blended with light-harvesting metallo-organic complexes with broad absorption spectra for efficient capture of the solar spectrum. These blends are impregnated into the titania nanotube arrays, while providing electrodes, to create the solar cells. The structure of these solar cells is discussed together with the effect of the structure on the cell properties and performance. Poster 45 Etch Rate and Profile Control in Silicon and Lithium Niobate by a Fluorocarbon ICP Technique for Micro-Optic Structures, Lirong Sun & Andrew Sarangan, University of Dayton, Electro-optics Program, 300 College Park Drive, Dayton, Ohio Fluorocarbon plasma etching with arbitrary depth
and profile independent of crystal orientation opens up significant
capabilities for micro-optic and MOEMS designs. In this research,
we investigate the etch rate and sidewall profile using the
Inductively Coupled Plasma (ICP) etching technique. The materials
being investigated are silicon, silicon dioxide and lithium
niobate. Micro-optic structures using different etch chemistries
such as CF4, CHF3, SF6 and Argon have been explored to achieve
a wide range of etch rates, sidewall angles, and surface roughness.
The sidewall profiles are adjusted by gas composition, ICP power,
pressure, bias power and etching time. Poster 46 Selective excitation of excitonic transitions in PTCDA crystals and thin films, V. R. Gangilenka, A. Desilva, Lyubov V. Titova, L. M. Smith Department of Physics, University of Cincinnati, Cincinnati, Ohio, R. Scholz Walter Schottky Institute, Technical University of Munich, 80333 Munchen, Germany, H. P. Wagner Department of Physics, University of Cincinnati, Cincinnati, Ohio We study various exciton transitions in PTCDA
crystals and in thin films at low temperatures (~5 K) by photoluminescence
excitation spectroscopy (PLE) using DCM and RG6 dyes. The investigated
PTCDA crystals are grown by sublimation and thin films are deposited
on Si substrate by organic molecular beam deposition (OMBD)
at high vacuum. The PLE excitation energy ranging from 1.878
to 2.172 eV enables the selective excitation of Frenkel excitons
and of charge transfer transitions between PTCDA molecules in
the same unit cell (CT1) as well as between stacked molecules
along the growth direction (CT2). The observed excitation energy
dependence of the emission bands supports the assignment of
the different recombination channels obtained from time resolved
PL measurements [1]. Poster 47 Coatings to Improve Surface Properties of Microcellular and Fibrous Carbon Structures, A.Karumuri*, D.Sharma, and S.M.Mukhopadhyay, Mechanical & Materials Engineering, Wright State University Formation of continuous and adherent ceramic coatings such as nitrides, carbides, and oxides on carbon structures can enhance many surface properties such as high temperature oxidation resistance, heat exchange, and bonding with other phases. Most currently used coating methods use complex vapor phase depositions involving toxic chemical precursors and undesirable by-products. The goal of this project is to investigate simple, non-toxic thin film deposition techniques that use benign precursors and/or nanoscale particles on uneven, high porosity graphite structures with a variety of oxidation resistant compositions. Carbon foams and fiber fabrics were coated with BN, SiC, Silica, and mixed phases. The effectiveness of each coating in surface property enhancements have been studied, and will be presented. Microstructure, composition, and chemical states have been characterized by Field Emission Scanning Electron Microscopy (FESEM) and X-Ray Photoelectron Spectroscopy (XPS). The quality of films obtained so far, and scope of future improvements will be discussed.
Reversible Photoinduced Magnetism in V-Cr Prussian
blue analogues, K. Deniz Duman, Jung-Woo Yoo, N.P. Raju, Department
of Physics, The Ohio State University, Columbus, Ohio, Amber
C. McConnell, William W. Shum, Kendric J. Nelson, Joel S. Miller,
Department of Chemistry, University of Utah, A.J. Epstein Department
of Physics and Chemistry, The Ohio State University, Columbus,
Ohio Chemical Vapor Deposition of Carbon Nanotubes on Copper Substrates, Ge Li1, Chaminda Jayasinghe1, Pravahan Salunke1, Emily Head1, Wondong Cho1, YeoHeung Yun2, Mark J. Schulz2, and Vesselin Shanov1, 1-University of Cincinnati, Chemical and Materials Engineering, Cincinnati, Ohio, 2-University of Cincinnati, Mechanical Engineering, Cincinnati, Ohio Vertically aligned Carbon Nanotubes (CNTs) on conducting substrates may find future applications in areas from electronic chip cooling, cryogenic pumps to thermal management in spacecrafts. The study is focused on advanced thermal interface materials (TIMs) for cooling and thermal management of electronic devices. The goal is to employ CNTs for enhanced thermal conduction across the interfaces. Vertically aligned CNT arrays were grown by Chemical Vapor Deposition (CVD) on copper substrates with multilayered structure on top. Prior the synthesis the substrate was studied by X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM) in order to understand the correlation between the surface properties of the substrate and the CNT growth. The CNTs were characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Raman Spectroscopy, and Thermal Gravimetric Analysis (TGA). The obtained results demonstrated that CNTs can be successfully grown on thermally and electrically conductive substrates.
Comparative Studies of the Optical Cross-Section
Spectra of the Rare Earth The integration of optics and microelectronics
on a single Silicon chip platform has been a dream for many
years. The most basic devices for the integration of optics
and electronics are the light sources, modulators, detectors
and waveguides [1]. There has been considerable interest in
recent years in using III-Nitride semiconductors doped with
rare earth ions for optoelectronics, phosphors and semiconductor
laser applications [2,3]. Trivalent rare earth ions (RE3+) were
successfully incorporated into GaN, AlN and their alloys resulting
in an efficient emission across the entire visible and near
IR spectral range. Among the most extensively studied were Eu,
Er and Tm doped different III-Nitride hosts. Although there
have been significant research efforts on the spectroscopic
and laser characterization of these materials, little work has
been performed on evaluating parameters like absorption and
emission cross sections for RE-doped III-Nitride thin films.
These parameters, which give the fictitious area interacting
with the electromagnetic radiation, are necessary to model the
devices with optimum efficiency [4]. The reduced dimension of
the active thin film layer, as is in the case of RE ions implanted
epilayers, has a much smaller number of the optically active
RE ions interacting with the radiation comparing with bulk counterparts
that makes absorption spectra measurement difficult in reflective
and transmission modes. Further, the rare earth doped nanosize
crystal hosts have even fewer active species when compared to
thin films making the measurement even tougher. In this presentation
the optical cross sections of the selected RE ions implanted
in GaN thin films and nanosize RE2O3 particles are calculated
from the measured luminescence spectra using Fuchtbauer- [1] A. Steckl, J. Park, J.Ho and J. Zavada Prospects
for Rare Earth Doped GaN Lasers on Si, Materials Today,Vol.
10, pp.20-27 (2007). Poster 51 Lightweight and Flexible Quantum Dot-Polymer Composites: Synthesis and Applications, Raj Makote, Nonstructural Materials Division, University of Dayton Research Institute (UDRI), Dayton Ohio When the size of the semiconductor crystalline material becomes smaller than the Bhor exciton radius, it exhibits a strong quantum confinement effect. The luminescence spectrum of a quantum dot is tunable and strongly dependent on dot size. We have investigated different pathways to synthesize quantum dots in a polymer matrix. CdSe, ZnS and PbS quantum dots were synthesized in transparent Sol-gel hybrid polymers as well as in PMMA, PDMS and Polystyrene matrices. The effect of molecular chain structure on the uniformity of quantum dot size and dispersion in the polymer matrix have been studied. Poster 52 Iron and Iron Nitrides on Wurtzite Gallium Nitride (0001), Wenzhi Lin, Jeongihm Pak, David C. Ingram, and Arthur R. Smith, Nanoscale & Quantum Phenomena Institute (NQPI), Department of Physics and Astronomy, Ohio University, Athens, Ohio In this report, we study and compare the epitaxial growth of iron and iron nitride on wurtzite (w)-GaN(0001) by using reflection high energy electron diffraction (RHEED) and other techniques. We have investigated the growth of ~ 1:1 (nominal concentration) FeN on w-GaN(0001) using rf N2 plasma molecular beam epitaxy (MBE) and monitored in-situ using RHEED; these recent results indicate that FeN grows epitaxially with [111]-orientation on w-GaN(0001) and that the film grows smoothly (two dimensional-like mode) up to the first two monolayers, after which it begins to relax while changing to a three-dimensional growth mode. The in-plane epitaxial relationship with the GaN substrate was determined to be [-110]FeN || [11-20]GaN and [11-2]FeN || [1-100]GaN, and the FeN was determined to have zinc-blende crystal structure. Fe metal on w-GaN(0001), as the end-point system of the spectrum, is also being explored. Initial results for Fe growth show a very streaky RHEED pattern, compared to the FeN film. It is also apparent that a multi-domain film structure arises in the growth process based on the multi-streak pattern. The XRD and RHEED studies suggest the films has body-centered cubic crystal structure, with epitaxial relationship of [110] Fe || w-GaN [0001], and [001] Fe || GaN <11-20>. The multiple streaks RHEED patterns are attributable to the multiple domains under such an epitaxial relationship. Poster 53 Photoluminescence Dynamics of GaAs/AlGaAs Core-shell Nanowires, S. Perera, M. Fickenscher, T. B. Hoang, H. E. Jackson, L. M. Smith, Department of Physics, University of Cincinnati Ohio, J. M. Yarrison-Rice, Department of Physics, Miami University, Oxford, Ohio, H. J. Joyce, Y. Kim, Q. Gao, H. H. Tan, C. Jagadish, Australian National University, Canberra ACT 0200, Australia, X. Zhang, J. Zou, University of Queensland, St. Lucia, QLD 4072, Australia We use time-resolved PL spectroscopy to study the exciton dynamics of GaAs/AlGaAs core-shell nanowires (NWs) at 20 K. NWs were prepared by Au catalyst-assisted MOCVD and a titanium-Sapphire laser (780nm) was used to excite the nanowire sample. PL emission from single NWs exhibits an excitonic peak at ~1.515 eV. The exciton lifetime depends on the morphology and crystallographic defect density of the GaAs core, which are in turn dependent upon the growth conditions. Nanowires cores grown at higher temperatures (450 C) give short exciton lifetimes (<100 ps). We reduce twin defects within the nanowire by using a new two temperature growth technique in which the core is nucleated at a higher temperature (450 C) for 1 minute and then grown at a low temperature (375 C) for 30 minutes. In addition, we deposit a 5nm GaAs cap around the AlGaAs shell which prevents oxidation of the shell. These twin-free minimally tapered nanowires achieved using a low growth temperature (375 C) exhibit high quantum efficiency with an exciton lifetime approaching 1.1 ns at 20 K. Support for this work was provided by NSF (#0701703) and the Australian Research Council. Poster 54 Synthesis of Ultrastable, Highly Luminescent
CdTe/CdS Core/Shell Nanocrystals, Colloidal CdTe nanocrystals are of interest for a variety of applications including bioimaging and diagnostics. The bulk band gap of CdTe is smaller than that of CdSe, making it better suited for imaging in biological tissues. Unfortunately, CdTe nanocrystals lose their fluorescence rapidly on exposure to air. For this reason, most studies involving high quality (i.e. highly luminescent and monodisperse) nanocrystals focus on CdSe. In this work, high-quality, airstable, CdTe nanocrystals were synthesized in a noncoordinating solvent, octadecene (ODE). The simple procedure provided very good quality nanocrystals with nearly monodisperse shape and size. Following preparation, a protective shell of CdS was added to the CdTe to protect the core from quenching by oxygen, water, or other reactive species. These core/shell nanocrystals maintain very high luminescence quantum yield after exposure to air and after transfer into aqueous phase through ligand exchange.
Peptide Ligands for Shape Control and Directed Assembly of Inorganic Nanocrystals, John D. Suter, Mary E. Eberly, and P. Gregory Van Patten, Department of Chemistry & Biochemistry and Nanoscience & Quantum Phenomena Institute, Ohio University, Athens, Ohio We describe a combinatorial panning procedure aimed at discovering peptide chains that exhibit selective binding to individual lattice planes of a given crystal with minimal binding to other surfaces of the same crystal. This extraordinary surface binding selectivity may allow for nanocrystal shape control and/or bottom up nanocrystal-assembly. Poster 56 e-mailed Poster 57 Experimental Evidence of Fermi-Luttinger Liquid
State via Coulomb Drag between Short 1D Wires., Mustafa Muhammad*,
Philippe Debray*, Steve Herbert**, Richard Newrock*,*Department
of Physics, University of Cincinnati, OH. We have measured Coulomb drag between two parallel, electrically isolated one-dimensional wires. The wires are spatially separated and are fabricated with GaAs/AlGaAs heterostructure with 2DEG in interface, using split-gate technique with the use of e-beam lithography, metal deposition and lift-off and various associated processing steps. Drag is measured between wires with 500 and 300 nm lengths in the 1D transport regime, in temperature range 28 mK – 1.2 K. We have observed both positive and negative drag. The temperature dependence of both drag types is in excellent agreement with that predicted by the recently proposed Fermi-Luttinger liquid (FLL) theory that takes into account of the curvature in the 1D dispersion. Positive drag occurs when the curvature is positive and negative drag occurs when it is negative. Poster 58 Non-Linear Conductance of A Short Quantum Point Contact, Tai-Min Liu, Maryam Torabi, Amir Maharjan and Andrei Kogan(1), Steven Herbert( 2) Michael Melloch (3), (1) Department of Physics, University of Cincinnati, Cincinnati, Ohio, 2Xavier University, Cincinnati, Ohio, 3Purdue University, West Lafayette, Indiana Abstract: We have measured non-linear conductance G of a very short, less than 80 nm lithographic length, quantum point contact as a function of the source-drain voltage Vsd and gate voltage Vg at the device lattice temperature T < 20 millikelvin. The lithographic width/length ratio of the QPC is approximately 2.5. We observe several well-resolved plateaus in G at Vds=0, but find no prominent zero-bias peak in G(Vds) reported by several groups in longer, lower aspect ratio contacts at near-opening gate voltage [1,2]. The peak is believed to arise due to Kondo-like correlations between a quasi-local magnetic state in the constriction [1,3] and the device "leads". Our data suggest that the quasi-bound spin state does not form in short QPCs and agree qualitatively with the recent predictions [3]. 1. S.M. Cronenwett et. al. "Low-temperature
fate of the 0.7 structure in a point contact: A kondo-like correlated
state in an open system". Physical Review Letters, 88(226805),
2002. Poster 59 Hybrid Functional Nanomaterial: POSS Functionalized Carbon Nanofiber, Javed A. Mapkar, Pallavi Iyer and Maria R. Coleman, The University of Toledo, Chemical & Environmental Engineering Department1, Toledo, Ohio Hybrid nanomaterials are broadly described as
multi-component system where two or more nanomaterials are integrated
to form a new nanomaterial having attractive multifunctional
properties. In this paper we discuss the formation of one such
hybrid nanomaterial based on carbon nanofiber (CNF) and polyhedral
oligomeric silsesquioxane (POSS). The octaaminofunctional POSS
(OAPS) were covalently attached on the surface of CNF to increase
the level of surface functionality and provide a platform for
further modification. The CNF-POSS hybrids were designed to
improve their interaction with the polymer matrix and to form
nanocomposite with enhance multifunctional properties. Poster 60 Reconfigurable Threshold Logic Gates Using Nanoscale DG-MOSFETs, Darwin T Ting & Savas Kaya, School of EE&CS, Ohio University, Athens OH 45701 Reconfigurable logic systems carry a special importance, especially in compact, low-power logic design, because they can implement alternative or supplementary logic operations without devoting additional resources in nanochips with already dense layouts. Threshold logic gates (TLG) are one of the prime examples of such reconfigurable logic systems with fine-grain re-configurability without needing specialized programming hardware or procedures. We designed very flexible and compact TLG circuits using nanoscale DG-MOSFETs and verified their operations using TCAD/SPICE mixed-signal simulations. We illustrate how input weights as well as evaluation thresholds can be readily altered in these novel TLG circuitry that can outperform the conventional counterparts. Poster 61 Novel Voltage & Current Controlled Oscillators Based on Nanoscale DG-MOSFETs, Anish Kulkarni & Savas Kaya, School of EE&CS, Ohio University, Athens OH 45701 Double-gate MOSFETs have intrinsic features such as local and dynamic threshold control via back-gate biasing, which make them ideally suited for voltage and/or current controlled oscillator designs. In this work we utilize these nanoscale transistors to design novel voltage-controlled (VCO and current-controlled oscillators (ICO) with reduced complexity and improved performance by using DG-MOSFETs in various innovative circuits and biasing schemes. Besides the traditional applications, such ultra-compact and highly-sensitive VCO and ICOs can become very efficient nanosensors that can be integrated with conventional and evolutionary CMOS platforms at the end of Silicon scaling. Poster 62 Vacancy Electronic Structure of Ag(lll), Danda P. Acharya', Kendal W. Clark, Kai-F. Braun, Saw-W. Hla, 0hio University, Physics & Astronomy Department, Athens, Ohio The surface electronic structure of Ag(lll) is important for the various catalytic reaction processes. Here we present the electronic structure of vacancies on Ag( 111) studied by means of low temperature scanning tunneling microscopy (STM) and spectroscopy at 4.6K. Vacancies with varying sizes are created on Ag(lll) :surface via controlled tip-sample contact. Then these vacancies are filled back with individual atoms which are extracted locally using STM tip, until the vacancies are completely filled. At each vacancy filling step, the conductance tunneling spectra are acquired to determine the associated electronic structure. We find that the depopulation of surface state occurs with increasing vacancy size and depth. The surface state signal is no longer detectable after 6 atomic layer deep vacancies. Furthermore, a new vacancy state is discovered whose energy decreases with the increasing vacancy size. This work is financially supported by the United States DOE, BES grant no. DE•FG02-02RR46012 and OU-BNNT. Poster 63 Nanofocusing of Surface Plasmons in Metallic Nanostructures, Weibin Chen and Qiwen Zhan,Electro-Optics Graduate Program, University of Dayton, 300 College Park, Dayton, Ohio 45469-0245 Plasmonic focusing with metallic nanostructures is an effective approach to confine optical field into nanometric size, which breaks the diffraction limit of light. Owing to strong spatial confinement and high field enhancement, plamonic focusing has important applications in near field optical imaging and sensing. Surface plasmon is an electromagnetic wave due to the interaction of light and metallic structures. As a wave phenomenon, surface plasmon can be focused using appropriate excitation geometry and metallic structures. We explored three different metallic structures for nanofocusing of surface plasmons with radial polarization illumination. When radially polarized beam is launched into these plasmonic structures, the entire beam is TM polarized with respect to the dielectric/metal interface, providing an efficient way to generate highly focused surface plasmon through constructive interference and creating an enormously enhanced local field. An evanescent nondiffracting Bessel beam can be obtained with planar metallic/dielectric interface. Plasmonic lens with conical shape and annular rings under radial polarization illumination are numerically studied with a finite-element-method model. The field distribution with a full-width-half-maximum as small as 10 nm and intensity enhancement of five orders of magnitude can be achieved with 633 nm optical excitation. We coupled the radia |