Bulletin of the American Physical Society
2008 Joint Fall Meeting of the New England Sections of APS and AAPT
Volume 53, Number 9
Friday–Saturday, October 10–11, 2008; Boston, Massachusetts
Session B2: Submitted Session II |
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Room: Campus Center, Third Floor 3545 |
Friday, October 10, 2008 1:00PM - 1:12PM |
B2.00001: Reflection of Electromagnetic waves on DPS/ DNG layers Joseph Shahbazian, Aram Karakashian We discuss the optical wave propagation in a one dimensional photonic crystal composed of alternating layers of anisotropic DNG and isotropic DPS materials. Here we have studied theoretically the transmission and reflection, the non Bragg band gaps, which are not based on interference, in a photonic crystal composed of alternating layers of DNG and DPS materials. Our center of attention is the study of the zero permittivity, zero permeability and zero average refractive index gaps.We find that this type of photonic crystal in the visible wavelength range exhibits negative refraction in a wide frequency range and has interesting properties to control propagation of electromagnetic waves. [Preview Abstract] |
Friday, October 10, 2008 1:12PM - 1:24PM |
B2.00002: Electronic Structure of Graphene layers on SiO2 J.H. Shahbazian, H.S. Choi, S.J. Woo, Y.-K. Kwon Using \textit{ab initio} density functional theory we investigate the electronic structures of single, double and triple layers of graphene on SiO$_{2}$ surfaces terminated either with Si or with O. After performing full geometry relaxation, we find that the first graphene layer is chemically bonded to the substrate and does not show any grapheme-like electronic structure. The graphitic electronic character is somewhat recovered by putting second and third layers of graphene, although subtle differences are observed among different stacking configurations, such as AA, AB, and ABC, and so on. These effects can be seen both on Si- terminated and O- terminated substrates. These studies would provide fundamental understanding to gives control over the band structure of graphene layers on SiO$_{2}$, and raises the potential application of graphene. [Preview Abstract] |
Friday, October 10, 2008 1:24PM - 1:36PM |
B2.00003: Non-Equilibrium Effect on Adsorption of Gold Nanoclusters Grown on \textit{p}-Aminothiophenol Self Assembled Monolayer on Gold Substrates Dipti Sharma, Marina Ruths This study explores the adhesion mechanism of gold nanoparticles (30 nm) tethered on gold substrates (100 nm) via self-assembled monolayers (SAMs) of $p$-aminothiophenol (ATP) using AFM and SEM. Adsorption of nanoparticles was studied as a function of \textbf{immersion time }(0\textbf{, }12, 24, 48 {\&} 72 h) \textbf{suspension concentration }(1.28*10$^{-10 }$M, 2.56*10$^{-10 }$M) and\textbf{ pH (}3, 4 in citrate buffer). The number of adsorbed nanoparticles increased as dipping time in the suspension increased and reached to the maximum value, hit the maximum, then decreased and showed a peak. This peak moved to lower time (by 12 h) as concentration of particles increased (doubled). As pH value increased from 3 to 4, peak shifted from 24 h to 48 h. We ascribe this to an electrostatic interaction between citrate-stabilized negatively charged nanoparticles and the protonated amino group of ATP. This interaction allows the nanoparticles to migrate and form clusters on the surface during long immersion times in the nanoparticle suspension and the stages of adsorption make the surface in non equilibrium state. As a control, 1,9-nonanedithiol (NDT) can be used at the place of ATP to avoid this non-equilibrium state on the surface. [Preview Abstract] |
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