An experimental and theoretical study on the adsorption behaviors of MHBA ions on silver nano-particles

Three models of m-hydroxybenzoic acid (MHBA) adsorbed on the surfaces of silver nano-particles were established. The first model is MHBA adsorbed on one Ag atom through the hydroxyl group; the second model is MHBA adsorbed on one Ag atom through the carboxyl group; and the third one is MHBA adsorbed on two Ag atoms through the carboxyl and hydroxyl groups. The Raman spectra of these third models using DFT-B3PW91 with lanl2dz were calculated; it was found that the calculated Raman frequencies were in good agreement with experimental values. So we can believe that the simplified models are probably reasonable to describe some surface-enhanced Raman experiments.