2008 NSTI Nanotechnology Conference and Trade Show - Nanotech 2008 - 11th Annual

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Clean Technology 2008

Enhanced Raman scattering of TNT and DNT on Ag Colloid Reduced with Sodium Citrate

J.I. Jerez-Rozo, S.P. Hernández-Rivera
University of Puerto Rico, Mayagüez, PR

SERS, silver colloid, plasmon

Surface-Enhanced Raman Scattering (SERS) provides extremely high sensitivity, due to increase in the Raman cross-sections of intrinsically very weak scattering events making these events comparable or even better than photon emission efficiencies found in fluorescence processes. The observation of vibrational spectra of adsorbed species on surfaces by SERS is one of the most incisive analytical methods for chemical and biochemical detection and analysis. The metallic nanoparticles that make SERS possible are of fundamental interest since they possess unique size-dependent properties (optical, electrical, mechanical, chemical, magnetic, etc.). These properties are quite different from the bulk and the atomic state. Silver colloids have been synthesized by chemical reduction method and have been used for detecting TNT and DNT in solution with high sensitivity and high molecular specificity [2,3]. The study focused on preparing metallic nanoparticles within size range in the 50-100 nm. The nanoparticles were characterized using UV-VIS spectroscopy, Scanning Electron Microscope (SEM) and Raman Spectroscopy. The detection of TNT and DNT was conducted via an indirect method that involved the alkaline hydrolysis of TNT and DNT in presence of a strong base (NaOH) [5]. This method offers the advantage of generating reaction products that provided enhanced detection in the presence of roughened surfaces (SERS). The detection of TNT degradation products was evaluated on silver colloids using excitation wavelengths 532 nm. The results revealed an increase in the intensity of the vibrational signals, attributed to the SERS spectra of degradation products that resulted from the alkaline hydrolysis of TNT and DNT. Bands associated to NO2 out-of-plane bending modes at ca. 820 and 850 cm-1 and NO2 stretching modes at 1300-1370 cm-1 were significantly enhanced [1,4].

Nanotech 2008 Conference Program Abstract