Characterization and photocatalytic activity of SiO2-TiO2 mixed oxide nanoparticles prepared by sol-gel method

SiO2-TiO2 mixed oxides have been prepared by sol-gel technique from titanium tetraisopropoxide and tetraethylorthosilicate. The prepared materials were characterized by X-ray diffraction, FT-IR spectroscopy, scanning electron microscopy, nitrogen physisorption and UV-vis diffuse reflectance spectroscopy. The results indicate that compared to pure TiO2, the SiO2-TiO2 mixed oxides show higher thermal stability, larger surface area, greater band gap energy and smaller crystallite size. The higher thermal stability of SiO2-TiO2 nanoparticles allows calcination of SiO2-TiO2 nanoparticles at higher temperatures without the accompanying phase transformations from anatase to rutile. The photocatalytic activity of the prepared materials has been compared in the photodegradation of new fuchsin (C.I. 42520) and amaranth (C.I. 16185). Effects of SiO2 concentration and calcination temperature on the photocatalytic activity of SiO2-TiO2 nanoparticles have been investigated. The photodegradation rate of new fuchsin in the presence of 40% SiO2-TiO2 nanoparticles calcined at 600 oC was higher than that observed with pure TiO2 and Degussa P25 TiO2 by 7.9 and 3.27 times, respectively.