Surface and photocatalytic properties of sol-gel derived TiO2@SiO2 core-shell nanoparticles

The surface of TiO2 nanoparticles was modified with silica prepared by acid hydrolysis of tetraethoxysilane followed by polycondensation. A comparative characterization of the initial and modified nanoparticles by TEM, XRD, specific surface area and zeta-potential measurements as well as the estimation of the surface acid-base properties via dynamic pH measurements revealed that the applied surface modification provided almost no changes in the phase composition, crystallite size range (similar to 16 nm) and mesostructure of the initial anatase nanoparticles, but resulted in a more than twofold increase in the specific surface area and change of the surface functionality from a prominent Lewis acidity toward a relatively weak Broensted acidity. The resulting TiO2@SiO2 "core-shell" particles are shown to exhibit a significant enhancement of singlet oxygen generation compared with the initial TiO2. In conjunction with increased specific surface and modification of the surface centers, this effect promoted a drastic growth of photocatalytic activity indicated by an almost 90% degradation of methylene blue dye upon UV irradiation. [GRAPHICS] .