Effects of solution conditions on the surface-enhanced Raman scattering of cyanide species at silver electrodes

Abstract

The effect of solution pH and supporting electrolyte anion on the SERS behavior of cyanide species adsorbed at Ag electrodes is described. Signals for the nu(CN) band are observed in both acidic (pH 2) and basic (pH 11) media in ClO/sub 4//sup -/, Cl/sup -/, and SO/sub 4//sup 2 -/ supporting electrolytes. The frequency and intensity of the nu(CN) band are a function of electrode potential in all media. The potential at which the SERS signal reaches a maximum intensity is slightly dependent on the anion of the supporting electrolyte in basic media, but is a strong function of the anion in acidic media. In acid solution, HCN is adsorbed. Two unresolved bands occur in the nu(CN) region in acidic media and several possible assignments are proposed. The assignment that best explains all of the experimental data involves both end-bonded and side-bonded HCN. The effect of supporting electrolyte anion on the SERS response is explained in terms of the relative abilities of these anions to influence the self-association of HCN in the interface.