Microstructural characterization of gold-doped silica-titania sol-gel films

Silica-titania coatings (up to 1.7 mu m thick) doped with gold metal particles were prepared via the sol-gel method. Acid-catalyzed solutions of methyltriethoxysilane and tetrabutoxytitanate were used as precursors. Gold nanoparticles were obtained in the oxide matrix by thermal reduction. The dimension and the shape of the particles were observed by high-resolution transmission electron microscopy and X-ray diffraction. The particles were spherical crystals with a measured crystallite size of about 18 nm They had a cubic structure with a lattice constant corresponding to Au. The homogeneity and the distribution in the coating of the gold were evaluated by secondary ion mass spectrometry and Rutherford backscattering spectrometry (RBS). The distribution of gold was found to be homogeneous with a slightly higher concentration towards the surface. The density of the silica-titania coating film and the gold fraction were measured by RBS.