Control of the photocatalytic activity of TiO2 nanoparticles by silica coating with polydiethoxysiloxane

A novel, simple and fast coating method that is based on microwave (MW) irradiation and which uses polydiethoxysiloxane (PDES) has been developed for TiO2 nanoparticles with the aim of reducing their photocatalytic activity. At the same time, silica coating was also carried out using a conventional solution method and the results of both methods were compared. The silica coated TiO2 nanoparticles were characterized by X-ray photoelectron spectroscopy (XPS), zeta-potential analysis, Fourier transform infrared spectroscopy (FT-IR) and high-resolution transmission electron microscopy (HR-TEM). For both coating methods, the extent of silica coating was found to depend upon the PDES loading; Si content increased with increasing concentration of PDES. Silica coating effectively reduced the photocatalytic activity of the TiO2 particles as evidenced by the color change of a mixture of non-coated and silica coated particles with 1,3-butanediol under UV radiation. The silica coated TiO2 nanoparticles obtained using the MW irradiation method showed higher inhibition of photocatalytic activity and superior UV-shielding characteristics than particles coated using the conventional solution method.