Role of surface metal clusters in SERS spectra of ligands adsorbed on Ag colloidal nanoparticles

The role of surface metal clusters in the surface enhanced Raman scattering (SERS) enhancement mechanism was investigated by coupling Raman measurements and DFT (density functional theory) calculations for pyrazole adsorbed on Ag colloidal nanoparticles. The adsorption process of the ligand can be suitably described by a model system constituted of pyrazolide anions chemically interacting with (Ag4)+2 surface clusters since the DFT approach allows a complete depiction of the SERS profile to be obtained, including both band frequencies and relative intensities.