Surface enhanced Raman scattering and theoretical characterization of the gallic acid anion silver surface interaction

Abstract A modified silver colloid allowed obtains to the best of our knowledge, the first surface enhanced Raman scattering spectrum of the gallic acid in aqueous solution at controlled neutral pH. The molecular electrostatic potential surface plot analysis allowed identifies the electrophilic attacking sites of the gallate anion. A combined charge transfer and electromagnetic mechanism of the Raman enhancement was inferred from the frontier high-low occupied molecular orbitals gap energy. Surface enhanced Raman scattering selection rules and theoretical calculations allowed propose that the gallic acid anion at pH 7 is oriented perpendicular to the surface with the carboxylate fragment driving the interaction.