The surface-enhanced infrared spectrometry of p-nitrothiophenol and its disulfide on silver films has been investigated by using deposition from solution, from self-assembled monolayers, and from the vapor phase using a direct-deposition gas chromatography/infrared (GC-IR) interface. In solution, the thiophenol oxidizes to form the disulfide, which then adsorbs to the silver film. If a silver film is deposited on top of a layer of the disulfide, the resulting spectrum is strongly different from that seen with a silver underlayer, more closely resembling the spectrum obtained from the self-assembled monolayer. When a GC-IR interface is used, the presence of the enhancement appears to be correlated with temperature-dependent chemisorption.
Gregory T. Merklin, Lin-Tao He, and Peter R. Griffiths, "Surface-Enhanced Infrared Absorption Spectrometry of p-Nitrothiophenol and its Disulfide," Appl. Spectrosc. 53, 1448-1453 (1999)