Bulletin of the American Physical Society
Joint Fall 2011 Meeting of the Texas Sections of the APS, AAPT, and Zone 13 of the SPS
Volume 56, Number 7
Thursday–Saturday, October 6–8, 2011; Commerce, Texas
Session F8: Condensed Matter Physics and Materials Research III |
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Chair: Charley Myles, Texas Tech University Room: Sam Rayburn Center Second Floor, Pride Room |
Friday, October 7, 2011 3:40PM - 3:52PM |
F8.00001: Surface Plasmon Enhancement of Organic Solar Cells David Shope, Jennifer Steele Organic photovoltaic (OPV) devices are inherently less efficient than silicon based devices. The short electron diffusion lengths in OPVs require the cells to be kept thin, diminishing their light absorption. One way to increase the absorption of these devices is to launch surface plasmons (SPs) along one of the electrodes at specific wavelengths in the solar spectrum. SPs are coherent electron oscillations that exist at the surface of a metal-dielectric boundary, and serve to focus light at the metal surface. This increase in absorption ultimately impacts the overall efficiency of the device. The OPV cells are fabricated on top of glass slides and consist of an organic heterojunction active layer residing between ITO and aluminum electrodes. SP coupling is achieved by forming sinusoidal gratings of various periods along the active layer/Al electrode boundary. Efficiency measurements of patterned and unpatterned samples were taken to determine if the gratings have any effect on the cell efficiency at the predicted wavelengths. No significant changes in efficiency have been observed, which could be due to the abnormally low efficiencies of the devices that were tested. [Preview Abstract] |
Friday, October 7, 2011 3:52PM - 4:04PM |
F8.00002: Structural Characterization of Humic Materials Using $^{13}$C NMR Techniques: A Comparison of Solution- and Solid-State Methods Catherine Clewett, Todd Alam, Eric Osantowski, Michael Pullin The analysis of the carbon type distribution and chemical structure of natural organic matter (NOM) by $^{13}$C NMR spectroscopy is an important technique for understanding its origins and reactivity. While prior work has used solution-state NMR techniques, solid-state NMR has the potential to provide this information using less instrument time and sample manipulation, while providing an array of advanced filtering techniques. Analyses of four isolated humic materials with $^{13}$C solid-state magic angle spinning (MAS) NMR techniques are described, including three commercially available samples and one fulvic acid sample isolated from the Rio Grande in New Mexico. This study demonstrates the utility of solid-state $^{13}$C NMR for aquatic NOM structural characterization, comparing these results to the existing solution-state determinations. The solid-state $^{13}$C MAS NMR results are used to determine {\%} carbon distribution, estimates of elemental composition ({\%}C, {\%}H, {\%}(O+N)), aromatic fraction (f$_{a})$, nonprotonated aromatic fraction (f$_{aN})$, an estimate of aromatic cluster size, and ratio of sp$^{2}$ to sp$^{3}$ carbons. A Gaussian deconvolution method is introduced that allows for a detailed analysis of carbon type. [Preview Abstract] |
Friday, October 7, 2011 4:04PM - 4:16PM |
F8.00003: Molecular design and MD simulations of epitaxial superlattice of self-assembling ternary lipid bilayers George Chou, Mark Vaughn, K. Cheng Multicomponent lipid bilayers represent an important model system for studying cell membranes. At present, an ordered multicomponent phospholipid/cholesterol bilayer system involving charged lipid is still not available. Using a lipid superlattice (SL) model, a 13 x 15 x 15 nm$^{3}$ ternary phosphatidylcholine/phosphatidylserine/cholesterol bilayer system in water with simultaneous headgroup SL and acyl chain SL at different depths, or epitaxial SL, of the bilayer has been designed with atomistic detail. The arrangements of this epitaxial SL system were optimized by only two molecular parameters, lattice space and rotational angle of the lipids. Using atomistic MD simulations, we demonstrated the stability of the ordered structures for more than 100 ns. A positional restrained system was also used as a control. This system will provide new insights into understanding the nanodomain structures of cell membranes at the molecular level. [Preview Abstract] |
Friday, October 7, 2011 4:16PM - 4:28PM |
F8.00004: Bonding of a silver sheath on textured-powder ribbons of green-state Bi-2212 superconductor Klaus Smit, Peter McIntyre, Kyle Damborsky, Feng Lu, Nathaniel Pogue A novel method is being developed for fabrication of textured-powder jelly-roll (TPJR) Bi-2212/Ag superconducting wire for applications in high-field magnets. In this process two silver foils must be fused together to enclose a ribbon of compacted, textured Bi-2212 fine powder. Fusing the silver foils must be accomplished with minimum heating of the superconducting powder filling. We are investigating methods using cold-welding, ultrasonic welding, and laser welding. Results of those investigations will be reported. [Preview Abstract] |
Friday, October 7, 2011 4:28PM - 4:40PM |
F8.00005: Spectroscopic and Ab-Initio Studies of $\pi $ -Type Hydrogen Bonding in Cyclic Alcohols and Amines Esther Ocola, Jaan Laane Infrared and Raman spectroscopy have been used to investigate several molecules capable of intramolecular $\pi $-type hydrogen bonding. Ab-initio calculations have been utilized to complement the experimental work. The cyclic alcohols, 3-cyclopenten-1-ol (3CYPO), 2-cyclopenten-1-ol, 2-cyclohexen-1-ol, and the cyclic amines, 3-cyclopenten-1-amine, 2-aminoindan, 2-cyclopenten-1-amine, 1-aminoindan, and 2-hydroxytetralin have been studied. 3CYPO can exist in four different conformational forms and all were observed in the infrared and Raman spectra. The conformer with the weak $\pi $-type intramolecular hydrogen bonding is about 400 cm$^{-1}$ (1.1 kcal/mole) lower in energy than the other three conformations to which the lowest energy form can interconvert through ring-puckering or internal rotation vibrations. The interconversions and relative energies of all the other molecules were also investigated. In each case the conformation with the lowest energy had a $\pi $-type hydrogen bonding. [Preview Abstract] |
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