SURFACE-ENHANCED RAMAN-SPECTROSCOPY OF CARBON ELECTRODE SURFACES FOLLOWING SILVER ELECTRODEPOSITION

Electrodeposition of Ag particles on glassy carbon (GC) resulted in up to a 100-fold enhancement of Raman scattering from the carbon substrate. The enhancement was a maximum when 0.21-mu-mol/cm2 of Ag was deposited and was greater when small (approximately 400-angstrom) Ag particles were present. Although the enhancement of carbon scattering was large, it was fragile, decaying with time after Ag deposition. On the basis of surface-enhanced Raman theory, the sampling depth of the enhanced spectra is approximately 20 angstrom, compared to ca 250 angstrom for conventional Raman of GC. SERS spectra of GC and pyrolytic graphite (PG) exhibited a stronger "disorder" band, either because the method is more surface selective or because the Ag preferentially deposits on electrochemically active surface defects. The approach was used to examine cleaved and laser-activated PG surfaces and polished highly oriented PG (HOPG), and it was demonstrated that laser damage is more extensive on the surface than the normal Raman spectrum implies.