EFFECTS ON SILVER-SURFACE-ENHANCED RAMAN-SPECTROSCOPY BY COMPETITIVE ADSORPTION OF HYDROXIDE AND HALIDE-IONS

The effect of the pH of a solution on the surface-enhanced Raman scattering (SERS) of halide species has been investigated in silver sol and at a silver electrode. The SER spectral changes observed were interpreted in terms of the competitive adsorption of hydroxide and halides, and the accompanying modification of surface properties. The competitive adsorption could be evidenced further from the pyridine/chloride system. With the increase of the pH of the solution, the surface halide concentration decreased letting the v1 (symmetric ring breathing) peak of adsorbed pyridine become more intense than the v12 (trigonal ring breathing) peak, and vice versa. The cyclic voltammographic study combined with the SERS data led us to conclude that a hydroxide ion cannot adsorb competitively with bromide on silver, while it can with chloride.