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1 November 1990 Surface-enhanced Raman spectroscopy of thiols and disulfides
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Aromatic and alkyl thiols adsorb on gold surfaces from ethanol to form stable monolayers. Surface-enhanced Raman spectroscopy (SERS) has been used to characterize the interactions of thiols and disulfides with gold surfaces immersed in aqueous solution. SERS provides the first direct evidence that thiols such as benzenethiol (thiophenol), benzenemethanethiol (benzylthiol), and 4-cyanobenzenemethanethiol adsorb dissociatively on gold, and interact with gold through the sulfur atom. The adlayers are quite robust, being stable between the potential required for the reduction of water and that required for oxidation of the gold substrate. Generation of hydrogen at the surface results in the formation of regions of low thiol coverage that are spectroscopically distinct from the high coverage regions that form spontaneously when the electrode is immersed in a thiol solution. The SER spectra of adsorbed aromatic thiols and the analogous disulfides are identical, indicating that the disulfide bond cleaves upon adsorption. SERS reveals that 4-bromobenzenethiol and 4-chlorobenzenethiol are reduced to benzenethiol at -1000 mV vs. SCE on gold. The corresponding 4-halo-benzenemethanethiols are reduced less readily, and 4-fluorobenzenethiol not at all. These reactions afford the possibility of preparing mixed thiol monolayers, and of subsequently modifying thiol monolayers in situ.
© (1990) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Robin L. Garrell, Cory Szafranski, and Weslene Tanner "Surface-enhanced Raman spectroscopy of thiols and disulfides", Proc. SPIE 1336, Raman and Luminescence Spectroscopies in Technology II, (1 November 1990);

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