Competitive Solvation and Chemisorption in Silver Colloidal Suspensions

Raman spectra and ab initio computational analysis involving Car–Parrinello molecular dynamics simulations and Density Functional Theory approach have been employed to obtain information on the behaviour of oxazole and thiazole in aqueous suspensions of silver nanoparticles, where solvation and chemisorption processes competitively occur. The solvation of both oxazole and thiazole is dependent on stable hydrogen bonds with water, mainly involving the nitrogen atoms of the heterocycles. The adsorption on silver colloidal nanoparticles is, instead, ensured by replacing water molecules of the aqueous environment with surface active sites that can be modelled as Ag 3 + clusters. These surface complexes can reproduce accurately the observed surface-enhanced Raman spectra, particularly concerning the most significant frequency-shifts with respect to the normal Raman spectra in aqueous solutions and the relative intensity changes.