Surface-enhanced Raman scattering studies of 1,10-phenanthroline adsorption and its surface complexes on a gold electrode

This paper reports on the interface processes of 1,10-phenanthroline (phen) at a roughened Au electrode by surface-enhanced Raman scattering (SERS) for the first time. Both the adsorption and coordination of phen on the roughened gold electrode have been studied. In comparison to the normal Raman spectrum of phen monohydrate, the frequency and relative intensity change significantly in the SERS spectra. As evidenced by cyclic voltammetry, the electrochemical behavior of the Au electrode is strongly modified by the adsorbed phen. It was found that a new pair of redox peaks appeared in the cyclic voltammogram only when both phen and X (X = Cl-, Br-) were present. Information on coordination bonds of Au-N and Au-X as well as on adsorbed bonds of Au-N-ad and Au-X-ad, was obtained by the SERS spectra. In situ SERS investigations together with electrochemical measurements convincingly prove the formation of surface complexes 1,10-phenAU(2)X(6) or [1,10-phenAuX(2)]AuX4 during the electro-oxidation process of Au while phen and X coadsorbed on the surface.