Surface-enhanced Raman scattering (SERS) spectra of pyridine adsorbed onto bare platinum and nickel electrodes in nonaqueous solutions are reported in this Letter. There are similarities and differences between the SERS from aqueous and nonaqueous solutions. The surface enhancement factor for platinum in acetonitrile solution has been calculated to decrease by a factor of ca. 10 compared with that in the aqueous media. The double-band character for the ring breathing mode is observed at 1009 and 1019cm-1. Two adsorption modes of pyridine on the platinum surface were assumed. Part of the pyridine molecules may be chemisorbed onto the surface, with the ring plane oriented vertical to the surface; other pyridine molecules may co-adsorb with lithium cations onto the surface.

Surface-enhanced Raman spectroscopy has been extended successfully to the study of a bare iron electrode (without any deposition of other noble metals) exposed to the neutral solution containing thiocyanate over a wide potential range from -1.8 to -0.4 V. The applied potential has a significant influence on the Raman frequency shift of SCN- as a result of the electrochemical Stark effect. Both N- and S-coordination modes were observed. Results show that at large negative potentials N-bound SCN- is favored, whereas at relatively positive potentials, S-bound thiocyanate predominates the iron surface. A sudden change in the d

Surface-enhanced Raman scattering (SERS) spectra of thiourea at an electrochemically activated iron electrode have been investigated as a function of applied potential. The marked downshift of the CS stretching and upshift of the NCN symmetric stretching by comparison of the SERS with the normal Raman spectrum of thiourea are clearly observed and interpreted by coordination of thiourea with the iron surface through sulfur atom. The appearance of the low-frequency mode at ca. 283 cm-1 assigned to the Fe-S vibration supports the assumption of S-coordination of thiourea. The orientation of thiourea molecules is assumed to be slightly inclined to the iron surface at an intermediate angle due to the observation of the SCNN out-of-plane bending band. Potential dependence of the SERS spectra shows that thiourea may interact more strongly with the iron surface at relatively positive potentials. Coadsorption of the supporting electrolyte anion ClO4 - with thiourea has also been confirmed by the SERS spectra.

The different initial interactions of benzotriazole (BTAH) with iron in both 0.5 M H2SO4 and simulated saline water (3.4% NaCl) have been investigated systematically by using a confocal microprobe Raman system, surface-enhanced Raman spectroscopy (SERS), and electrochemical potentiodynamic polarization curves. The SERS spectra of BTAH at the bare iron electrodes in both 0.5 M H2SO4 and simulated saline water have been obtained successfully for the first time. Electrochemical measurements show that the inhibition efficiency of BTAH is higher in saline water than that in acid solution, which is in accordance with the identification of the surface interaction on the basis of the SERS data. BTAH may be physisorbed onto the iron surface through its neutral molecule form or protonated BTAH2 + ions. While in saline water, the formation of the surface coordination compound characterized as Fe(II)-BTA may contribute to the outstanding spectral features. A cleavage of the NH bond is believed to occur while adsorption of BTAH onto iron proceeds. This more compact surface film results in a higher inhibition efficiency in comparison with that in an acid solution.

Surface-enhanced Raman scattering from a silver electrode in solution of 0.1 M LiClO4 in acetonitrile has been analyzed as a function of applied potential. Three m (O-H) bands associated with the interfacial water and two m (O-H) bands associated with the OH ion species were observed depending on the electrode potential. The band at 3487cm 1 is favored at relatively positive potentials and assigned to H2O molecules interacting with the electrode surface via the oxygen atoms. Another band at 3586cm 1 appears in a wider potential region and is assigned to the H2O molecules with one or both of the hydrogen atoms facing the electrode surface. Additionally, evidence for the possible surface ion pair, Li