[Surface-enhanced Raman scattering (SERS) of amino acids on silver colloid]

The surface-enhanced Raman spectra of glycine, valine and lysine adsorbed on silver colloidal particles and the Raman spectrum of lysine in aqueous solution were obtained. The adsorption was accompanied by the appearance of the 238 cm(-1) band corresponding to the oscillation of the molecule-metal chemical bond and indicating chemisorption of the amino acid. In the surface-enhanced Raman spectra of three amino acids, the peak bands at 900-930 cm(-1), near 1100 cm(-1) and near 1400 cm(-1), corresponding to the carbon-carbon bond, carboxyl and amino group vibrations, respectively, were markedly increased on the silver colloidal particles. It means that the Raman spectra of polar groups such as COO-, N2 and C-COO- were strongly enhanced via the carboxyl group. There was no influence under the low pH condition in the experimental system used.