Jerez Rozo, Jackeline I.

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    Enhanced Raman Scattering of TNT on nanoparticles substrates: Ag, Au and Au/Ag Bimetallic colloids prepared by reduction with sodium citrate and hydroxylamine hydrochloride
    (2007) Jerez Rozo, Jackeline I.; Hernández Rivera, Samuel P.; College of Arts and Sciences - Sciences; Castro Rosario, Miguel E; Mina Camilde, Nairmen; Department of Chemistry; Narinder, Mehta
    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. Bimetallic nanoparticles are of particular interest since they combine the advantages of the individual monometallic counterparts. Metal colloids have become the most commonly used nanostructures for SERS. Gold, silver and Ag/Au bimetallic alloys colloids have been synthesized by chemical reduction methods and have been used for detecting TNT in solution with high sensitivity and high molecular specificity. The study focused on metallic nanoparticles within size range in the 50-100 nm. The nanoparticles were characterized using UV-VIS spectroscopy, Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) and Raman Spectroscopy. The detection of TNT was conducted via an indirect method that involved the alkaline hydrolysis of TNT in presence of a strong base (NaOH). 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 gold, silver and silver/gold bimetallic colloids using excitation wavelengths of 785 and 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. 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 detected.