Photoresponsive formation of gold particles in silica/titania sol-gel films

Fine gold (Au) particles were formed by photochemical and ther mal processes in silica/titania glassy films. Photoreduction and/or thermal gelation of films dip-coated from silica/titania precursor solutions including Au(III) ions yielded gold particles. Particle formation was accompanied by changes in the surface plasmon band. The size and morphology of the particles were affected by the titania content of the mixture matrix films as well as by the gelation temperature. With higher titania contents and at higher temperatures the particle formation was accelerated and accompanied by a red shift of the absorption band. This particle formation occurred by diffusion and reduction of the doped Au(III) ions, both of which were promoted at higher titania contents. The controllable photodeposition process enabled us to form micropatterns of Au particles by using photomasks.