Surface-enhanced Raman Scattering and surface-enhanced resonance Raman scattering exciation profiles of Ag-2,2'-bipyridine surface complexes and of [Ru(bpy)(sub 3)](super 2+) on Ag colloidal surfaces: manifestations of the charge-transfer resonance contributions to the overall surface enhancement of Raman scattering

Surface-enhanced Raman scattering (SERS) spectra and excitation profiles of one of Ag-2,2'-bipyridine surface complex show a selective enhancement of several fundamentals, overtones and combination bands that manifests itself by a distinct maximum at ca. 540 nm on their excitation profiles. The results show that the magnitude of the charge transfer (CT) resonance enhancement in a system in which the CT and the electromagnetic (EM) mechanism operate simultaneously is comparable to that achieved in a system in which the CT resonance is the only enhancement mechanism.