Visible-light-induced patterning of Au– and Ag–TiO₂ nanocomposite film surfaces on the basis of plasmon photoelectrochemistry

A novel technique for patterning based on visible light at Au–TiO₂ and Ag–TiO₂ nanocomposite film surfaces has been developed for the first time. TiO₂ films loaded with Au and Ag nanoparticles were modified with hydrophobic thiols to obtain hydrophobic surfaces. The surfaces were converted to hydrophilic by visible light irradiation. Hydrophobic/hydrophilic patterning was also possible by visible light irradiation through a photomask. The patterning was due to removal of the thiol based on plasmon photoelectrochemistry. Visible-light-induced plasmon resonance at the Au and Ag nanoparticles gives rise to charge separation and redox reactions. The thiol is removed from the Au–TiO₂ film probably by oxidative desorption, and from the Ag–TiO₂ film owing chiefly to oxidation of Ag nanoparticles to Ag⁺.