Bulletin of the American Physical Society
Joint Spring 2011 Meeting of the New England Sections of the APS and the AAPT
Volume 56, Number 2
Friday–Saturday, April 8–9, 2011; Lowell, Massachusetts
Session F2: Materials, Devices, and Applications |
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Chair: Mengyan Shen, UMass Lowell Room: Olney Science Center 0-517 |
Saturday, April 9, 2011 8:00AM - 8:12AM |
F2.00001: Magnetic studies of S=1/2 kagom\'{e} lattice single crystals Tianheng Han, Joel Helton, Andrea Prodi, Claudio Mazzoli, Peter Muller, Deepak Singh, Jose Rodriguez, Collin Broholm, Danial Nocera, Shaoyan Chu, Young Lee The Zn-paratacamite mineral family, Zn$_{x}$Cu$_{4-x}$(OH)$_{6}$Cl$_{2}$, presents a promising system for studies of frustrated magnetism on a S=1/2 kagom\'{e} lattice. Here we report a new synthesis method, by which high quality single crystals of Zn-paratacamite can be produced. The x = 1 mineral herbertsmithite is a spin-liquid candidate. This compound displays a magnetic susceptibility that is anisotropic at high temperatures. A small anisotropy is observed in specific heat measurements with magnetic field applied in-plane and normal-to-plane. Inelastic neutron scattering has been performed and we will discuss the observed structure factor in the context of various theoretical expectations. [Preview Abstract] |
Saturday, April 9, 2011 8:12AM - 8:24AM |
F2.00002: Activated kinetics of the Crystalline to Nematic (K-N) and Nematic to Isotropic (N-I) phase transitions of Pentylcyanobiphenyl (5CB) liquid crystal Dipti Sharma Activated kinetics of the crystalline to Nematic (K-N) and the Nematic to Isotropic (N-I) phase transitions of the Pentylcyanobiphenyl (5CB) liquid crystal are discussed here. A kinetic comparison of the same types of transitions of other family member with higher number of carbon atoms i.e. Octylcyanobiphenyl (8CB) are also made to see the difference between the kinetic behavior of the above two transitions of the liquid crystals. Experiments were performed using high resolution calorimetric technique for heating and cooling runs. Two different scans i.e. Temperature scans and Rate scans were performed for 5CB and 8CB from 280 to 333 K at various rates to get the detailed behavior of the transitions. As a result, Double activation was observed for 5CB for two heating rate regimes whereas 8CB indicated single activation only. The 5CB has smaller enthalpy and entropy of the transitions and needs larger activation than 8CB. This kinetic change can be explained in terms of the length scale and mobility of the liquid crystal molecules. [Preview Abstract] |
Saturday, April 9, 2011 8:24AM - 8:36AM |
F2.00003: The Role of Localized and Propagating Surface Plasmons in Periodically-Arrayed NAnopillars Francisco Bezares, Joshua Caldwell, Orest Glembocki, Ronald Rendell, Mariya Feygelson, Maraizu Ukaegbu, Richard Kasica, Loretta Shirey, Nabil Bassim, Charles Hosten Periodically-arrayed nanopillars have been shown to exhibit evenly distributed electromagnetic (EM) fields and some of the largest average surface-enhanced Raman Scattering (SERS) enhancements reported for large-area nanostructures, making them ideal for optical sensors. Although these characteristics are thought to be the result of the combined contributions from localized (LSP) and propagating (PSP) surface plasmons, the degree to which each of these modes impacts the SERS enhancement efficiency of such nanostructures is unclear. To better understand the roles that LSPs and PSPs play in the SERS process, we have measured the SERS enhancement from periodic arrays of Au-coated Si nanopillar arrays that either feature both types of modes and those with only isolated LSP modes. These results illustrate that although the optimal nanopillar diameter (e.g. SPR condition) is determined primarily by the LSP modes, cooperative interactions between LSP and PSP modes result in at least an order of magnitude increase in the average enhancement factor and a broadening in the diameter response (e.g. increased SPR linewidth). [Preview Abstract] |
Saturday, April 9, 2011 8:36AM - 8:48AM |
F2.00004: Development of a Fabrication Path for Au-Organothiol-Carbon Nanotube Molecular Junctions Jason Moscatello Silicon electronics is at the scaling limit and new approaches are necessary. Nanomaterials have significant promise in addressing this problem and each has its own potentially useful properties; yet making the material is only the first step in harnessing those properties. Transitioning from developing materials to integrating them into devices is no small endeavor - placement, wiring, etc. are nontrivial on the nanoscale. This talk details work done at Michigan Tech developing a fabrication process for Molecular Electronic Junctions (MEJs). The goal is to study the lifetime of MEJs containing strong bonds because short lifetime is the largest limiting factor in many MEJs. It is important that the physics studied remains accurate even if the size is scaled down and the MEJs are arranged into arrays - two things that are necessary for MEJs to be used commercially. In addition the process is widely usable, since it only utilizes inexpensive and/or common processes (e.g. dielectrophoresis and photolithography). An overview of the fabrication process will be detailed, along with carbon nanotube (top electrode) placement by dielectrophoresis, and initial results. [Preview Abstract] |
Saturday, April 9, 2011 8:48AM - 9:00AM |
F2.00005: Enhanced efficiency in dye sensitized solar cells using reduced graphene oxide-TiO$_{2}$ nanocomposites Soumitra Satapathi, Lian Li, Ravi Mosurkal, Lynne Samuelson, Jayant Kumar Graphene, in the last few years, has elicited considerable interest for its remarkable electronic and optical properties. It has possible applications in the fabrication of organic solar cells, single molecule sensing and field effect transistors. Here, we, report the synthesis of graphene oxide starting from graphite nanoplatelets using Hammer's method. Subsequently, graphene oxide was reduced by hydrazine to obtain chemically reduced graphene oxide. The reduced graphene oxide-TiO$_{2}$ nanocomposites were prepared by physically mixing Triton-X stabilized reduced graphene aqueous dispersion and TiO$_{2 }$(P25) nanoparticles. Dye-sensitized solar cells (DSSC) were fabricated. It was observed that incorporation of 1wt{\%} graphene into TiO$_{2}$ leads to 16{\%} enhancement of overall power conversion efficiency. [Preview Abstract] |
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