Synthesis and characterization of silica-titania core-shell particles

Nearly monodispersed particles of silica were prepared and coated with uniform layers of titanium dioxide in anatase phase by hydrolysis and condensation of titanium butoxide. The coating thickness could be altered by adjusting the concentration of reactants (titanium butoxide and water) and the amount of added silica particles. Different coating thicknesses were deposited and studied using optical absorption spectroscopy, electron microscopy and Fourier transform infra-red spectroscopy. It was found that silica particles of size 170 +/- 5 nm were coated with 23 +/- 5 nm thick layer of titanium dioxide. Alternatively titania particles of size 340 +/- 5 nm were synthesized by controlled hydrolysis of titanium ethoxide in the presence of sodium chloride. These particles were further coated with 135 +/- 5 nm thick layer of silica to investigate changes in properties after changing the shell material.