Intensely-scattering phase in surface-enhanced Raman scattering by cyanide on gold electrodes

Abstract

Surface-enhanced Raman scattering (SERS) by cyanide on gold and silver electrodes in 0.1 mol dm^–3 KOH, 0.1 mol dm^–3 KCN appears to arise from metal oxide–cyanide compounds and not from cyanometal complexes. The similarity of v(CN) for the two metals indicates that metal(ion)–cyanide interactions within the SERS compounds are relatively unimportant. Possible involvement of cyanogold(I) complexes {e.g.[Au(CN)₂]^–} is ruled out by substantial differences between the v(CN) band for the SERS phase (ca. 2110 cm^–1) and for these complexes (>2164 cm^–1). The existence of analogous SERS compounds for both silver and gold is indicated by similar SERS frequencies under both controlled-potential and withdrawn (dry)-electrode conditions for the two metals. The involvement of a hydrolysed component (oxide/hydroxide) in gold/cyanide SERS is suggested by previous electrochemical studies of the gold dissolution system and by the similarity of gold/cyanide SERS to SERS from the system Ag/0.1 mol dm^–3 Na₂SO₄, 0.1 mol dm^–3 KCN, which appears to arise from a hydrolysed cyanide compound. Some indications of laser damage exist in the gold/cyanide SERS system, which is classified as an SERS type III (inorganic microzone).