Surface-enhanced Raman scattering from ferrocyanide and ferricyanide ions adsorbed on silver and copper colloids

Surface-enhanced Raman scattering has been observed from the adsorption of ferrocyanide (hexacyanoferrate(II)) and ferricyanide (hexacyanoferrate(III)) ions on Ag and Cu colloids and electrodes. Both ferrocyanide and ferricyanide ions interact strongly with Ag and Cu surfaces, and are bonded to surfaces via the end-on bridging CN σ-bondings. Chemisorption lowers site symmetry of the adsorbed states, resulting in the activation of Raman forbidden modes in the low-frequency as well as the nitrile-stretching regions.