Microemulsion Synthesis of Nanosized SiO2/TiO2 Particles and Their Photocatalytic Activity

Nanosized TiO2 and SiO2/TiO2 particles were synthesized by hydrolysis of tetrabutyl titanate and tetraethyl orthosilicate in a Triton X-100/n-hexanol/cyclohexane/ammonia reverse microemulsion. The particles were characterized by X-ray diffraction, Fourier transform infrared spectroscopy (FT-IR), and transmission electron microscopy. The photocatalytic activity was evaluated by photocata-lytic degradation of methyl orange under UV light irradiation. The effects of SiO2 content, crystal structure, and crystallite size on the photocatalytic activity were investigated. From FT-IR analysis, a new band at 950 cm−1 for Ti-O-Si vibration was observed. The Ti-O-Si bond and amorphous SiO2 suppressed the phase transformation of titania from anatase to rutile, increased the stability of anatase TiO2, and inhibited the crystallite growth. The average size of titania decreased from 38.4 nm in pure TiO2 to 3.9 nm in SiO2/TiO2 with a SiO2/TiO2 molar ratio of 2/1. In addition, the photocatalytic activity decreased with an increase of rutile content. SiO2/TiO2 particles with a SiO2/TiO2 molar ratio of 1/7 showed the highest photocatalytic activity for the photocatalytic degradation of methyl orange.