Surface enhanced raman and resonance raman spectroscopy in a non-aqueous electrochemical environment: Tris(2,2′-bipyridine)ruthenium(II) adsorbed on silver from acetonitrile

This letter reports the first observation of both surface enhanced Raman scattering (SERS) and surface enhanced resonance Raman scattering (SERRS) from the transition metal complex tris(2,2′-bipyridine)ruthenium (II), Ru(bpy)₃²⁺, adsorbed on a silver electrode from acetonitrile (ACN). The assignment of these spectra as valid examples of SERS and SERRS in a non-aqueous environment is based on the following criteria: (1) in situ demonstration of monolayer surface coverage of Ru(bpy)₃²⁺ using double potential step chronocoulometry (DPSCC); (2) the Raman signals are most intense after surface roughening by anodization; (3) the Raman spectra are potential dependent in the non-faradaic potential region; (4) the measured enhancement factors are greater ilian 10⁶; (5) the surface spectra are frequency shifted relative to their bulk counterpart; and (6) several other molecules also exhibit non-aqueous SERS and SERRS behavior. These results are highly significant in that generality of surface enhanced Raman spectroscopy has been extended into the rich domain of nonaqueous electrochemistry.