A comparative study on the adsorption behaviors of PABA in the silver nano-particles

Surface-enhanced Raman scattering (SERS) spectra of P-Aminobenzoic Acid (PABA) adsorbed on the silver nano-particles were studied, respectively, in the silver colloidal solution and on the dried silver-coated filter paper. To further study the adsorption behaviors of PABA on the different substrates, we analyze the problem by means of theoretical calculation. Five models of PABA adsorbed on the surfaces of silver nano-particles were established. The Raman spectra of these five models using DFT-B3PW91 with lanl2dz were calculated. By comparing the theoretical values with the experimental values, we found that the calculated Raman frequencies of the models were in good agreement with experimental values, respectively. So we can believe that the simplified models are probably reasonable to describe some surface- enhanced Raman experiments.