Surface-enhanced Raman scattering of p-nitrothiophenol -: Molecular vibrations of its silver salt and the surface complex formed on silver islands and colloids

The interpretation of the surface-enhanced Raman scattering (SERS) spectra of p-nitrothiophenol (p-NTP) is reported. SERS spectra were obtained by vacuum evaporation and casting of p-NTP onto silver island films, and also from colloidal silver solutions. The vibrational spectra of the silver salt (p-NTP-silver) were obtained for a direct comparison with the SERS of p-NTP chemically adsorbed onto Ag. Chemisorption of p-NTP through S-Ag bonding is indirectly proven by the disappearance of the S-H stretching mode. The Raman scattering spectrum of the silver salt is in good agreement with the SERS spectra of the silver surface complex. The spectral interpretation was aided using density functional theory calculations of the molecular spectra of p-NTP and that of the Ag-p-NTP. (C) 2001 Elsevier Science B.V. All rights reserved.