Preparation of well-defined titania-silica spherical particles

Well-defined 200 nm size titania-silica (Si/Ti atomic ratio of 0.19-1.5) spherical particles containing octadecylamine (ODA) were prepared by the hydrolysis and co-condensation of titanium tetraisopropoxide and tetraethoxysilane in the presence of ODA. ODA was extracted from the spherical particles using acidic ethanol to obtain nanoporous particles. The nanoporous titania-silica particles were calcined at 800 °C for 1 h to obtain nanoporous titania-silica particles composed of anatase crystallites and amorphous silica. Depending on the Si/Ti ratio, the size of anatase crystallites varied: 10 nm for the titania-silica particles at the Si/Ti ratio of 0.19 and 2 nm for those at the Si/Ti ratio of 1.5. The efficiency of photocatalytic decomposition of methylene blue was remarkably suppressed when the titania-silica particles at the Si/Ti ratio of 1.5 were used, though the bandgap absorption was possible at the same wavelength region for all the products.