SURFACE ENHANCED RAMAN EXAMINATION OF CARBON ELECTRODES - EFFECTS OF LASER ACTIVATION AND ELECTROCHEMICAL PRETREATMENT

Surface enhanced Raman spectroscopy (SERS) was used to examine carbon electrode surfaces following electrodeposition of 0.2-mu-mol/cm2 of metallic silver. As demonstrated previously, the resulting ca. 400-angstrom Ag particles increase the Raman scattering intensity from the carbon substrate by 30-100 times, or larger for special cases. In the current report, the technique was used to characterize the surfaces of laser activated and electrochemically pretreated (ECP) glassy carbon (GC) and highly ordered pyrolytic graphite (HOPG). The SERS spectra were more surface selective than normal Raman and more closely correlated with electrochemical observations. For laser-activated HOPG, the SERS spectra revealed damage to the graphite lattice at lower power densities, and the disorder exhibited in SERS spectra more closely tracked the increase in electron transfer rate. For ECP of GC, HOPG, and pyrolytic graphite, the surface film examined with SERS was indistinguishable for the three substrates. Finally, the damage resulting from ECP of HOPG is consistent with a nucleation and growth mechanism.