The preparation of silica–titania core–shell particles and their impact as an alternative material to pure nano-titania photocatalysts

In this study spherical core–shell particles in the range 200–800 nm were prepared. Heterocoagulation method was applied to deposit nano-crystalline titania on monodisperse Stöber silica spheres. Silica and titania were synthesized separately via sol–gel processes. Titania was obtained from tetrapropyl orthotitanate and titanium tetrachloride as the precursors. Particle sizes were analysed by photon cross correlation spectroscopy. Deposition of titania on the surface was verified by transmission electron micrographs. The extent of coverage was analysed by zeta-potential measurements and varied between 40 and 90%. The degradation of an aqueous methylene blue solution confirmed photocatalytic activity of the particles.