Adsorption and aggregation of gold nanoparticles onto poly(4-vinylpyridine) film revealed by Raman spectroscopy

The adsorption and aggregation processes of Au nanoparticles on a poly(4-vinylpyridine) (P4VP) polymer surface has been investigated by means of atomic force microscopy (AFM) and Raman scattering spectroscopy. According to the AFM images, the number of Au nanoparticles adsorbed on a P4VP film increased almost linearly with time up to 6 h of immersion time. On the other hand, the P4VP film was too thin to observe its normal Raman spectrum, but the Raman peaks of P4VP could be detected upon the adsorption of Au nanoparticles onto the film, definitely due to the surface-enhanced Raman scattering (SERS) effect associated with the localized surface plasmon of Au nanoparticles. Thereby, Au nanoparticles present in wet conditions on the P4VP film were shown to aggregate when the solvent was evaporated.