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10 September 2010 Cysteamine coated Ag and Au nanorods for improved surface enhanced Raman scattering from dinitrotoluene and trinitrotoluene
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Surface-enhanced Raman scattering (SERS) from trinitrotoluene and other nitro-based explosives is important for the development of a reliable detection scheme exhibiting low false-positive rates. However, the interaction of these compounds with Ag and Au causes the molecules to orient in ways such that the primary vibrations of the nitro groups, the main identifying Raman marker of these compounds, are inhibited in addition to causing a reduction in the SERS response. It has recently been shown that cysteamine, which contains amine functional end groups, will electrostatically attract the nitro groups of TNT. Therefore, as the thiol functional group of cysteamine chemically bonds this molecule to the plasmonically-active Au and Ag nanoparticles studied, SERS of TNT can be obtained following the nitro-amine functional group complex formation. It is observed that the cysteamine adsorbs in one of two configurations on the metal surface, with the trans configuration consisting of bonding at the S end of the molecule and the cysteamine is perpendicular to the metal surface, while in the Gauche configuration S bonding occurs, but the molecule bends over towards the metal film surface, approaching the parallel configuration allowing the amine groups interact with the surface. We find that the trans configuration is best for the detection of SERS from TNT. Experiments compare well with DFT calculations of the cysteamine and TNT complex and their adsorption on Ag.
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O. J. Glembocki, M. Gowda, S. Geng, S. M. Prokes, N. Y. Garces, J. Cushen, and J. D. Caldwell "Cysteamine coated Ag and Au nanorods for improved surface enhanced Raman scattering from dinitrotoluene and trinitrotoluene", Proc. SPIE 7757, Plasmonics: Metallic Nanostructures and Their Optical Properties VIII, 77570I (10 September 2010);

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