Raman spectroscopic studies of a thionine-modified electrode

Abstract

Raman spectroscopy has been used to determine the structure of the surface coat of a thionine-modified gold electrode. Spectra have been observed from the thionine form of the coat; no spectra could be obtained from the leucothionine form. Evidence is presented to show that the surface coat exists as a polymeric film with the individual thionine units linked via an amino nitrogen in a secondary amine structure. There is no evidence of chemical bonding between the film and the electrode. Raman spectroscopy has also been used to study the movement of charge through the film as it is oxidised and reduced. Observed spectra are shown to be due to a combination of resonance- and surface-enhanced Raman scattering. No spectra could be obtained from either the thionine or the leucothionine forms of a thionine-modified platinum electrode.