SERS active Ag-SiO2nanoparticles obtained by laser ablation of silver in colloidal silica

Very stable Ag-SiO2 nanoparticles were first obtained by laser ablation of a silver target in aqueous colloidal dispersion of silica, and examined by UV-vis absorption, TEM microscopy and Raman scattering. The SERS activity of these nanocomposites was tested by adsorption of 2,2’-bipyridine as molecular reporter, by excitation in the visible and near-IR spectral regions. The computational DFT approach provided evidence for the ligand adsorption on positively charged adatoms of the silver nanostructured surface, in close similarity with the metal/molecule interaction occurring in the corresponding Ag(I) coordination compound.