Formation and aggregation of photolytic gold nanoparticles at the surface of chitosan (CTO) films have been investigated. When thin films of chloroauric acid salt of CTO were irradiated with UV light in wet air at room temperature for 10 min, gold nanoparticles of ∼10 nm size are formed at the film surface. Detailed X-ray photoelectron spectroscopy (XPS) study and field emission type scanning electron microscopy (FE-SEM) observation have been carried out to characterize gold nanoparticles at the film surface. The shift of Au(4f) peak to the higher energy side and broadening of full width at half-maximum in the XPS spectrum are the direct evidence of the existence of gold atoms and small clusters in the early stage of photolysis. According to FE-SEM observation, growth in the particle diameter and aggregation of nanoparticles were observed after prolonged irradiation, and, finally, the film surface was densely covered with gold particles of 20−100-nm size. Gold atoms and clusters could move in the film and precipitate to the irradiated surface. Chemical composition analysis further suggests that gold particles at the surface are covered with an ultrathin CTO layer, which is partly oxidized by oxygen and chlorinated by chlorine during photochemical reactions.

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A bright silver mirror was formed by photolysis of silver salt of carboxymethylcellulose with 253.7 nm light. The silver metal film was proved to be useful for the substrate to deposit dye monolayers. Fluorescence quenching of rhodamine B on the silver metal film was interpreted in terms of excitation energy transfer.

A Raman signal arising from carboxylate ions in thin films of silver salt of carboxymethylcellulose (CMCAg film) was fairly increased, when the CMCAg film was photolyzed with UV-light. The maximum enhancement was achieved in the CMCAg film irradiated for 180 min. It is likely that the intensity enhancement of the carboxylate ions reflects the contribution of surface-enhanced Raman scattering (SERS).