Synthesis and structural, optical and electrical properties of TiO2/SiO2 nanocomposites

Sole components of titania (TiO2), silica (SiO2) nanoparticles, and binary TiO2–SiO2 nanocomposites with various molar ratios of silica contents were prepared by modified sol–gel method. The samples were calcined at 500 °C for 5 h and characterized by X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), UV–Vis spectroscopy, Brunauett–Emmett–Teller (BET), and photoconductivity. The crystallite size for TiO2/SiO2 nanocomposites was calculated using Scherrer’s formula and found to be 5 nm for TiO2 nanoparticles. The binary oxide shows the anatase type of TiO2 at the mole ratio up to 80 mol% of TiO2 added. The band gap for as-synthesized nanocomposites was calculated and it was found that the band gap decreases with increase of SiO2 content and then decreases with excess SiO2 content. FTIR confirms that both TiO2 and SiO2 phases have been formed. The BET surface area for TiO2/SiO2 nanocomposite is found to be 303 m2/g, and pore size distribution has an average pore diameter about 10 nm for 40 mol% of TiO2 added. It also confirms the absence of macropores and the presence of micro and mesopores. The field-dependent dark and photoconductivity studies reveal that the dark and photocurrent increase linearly with applied field confirming the ohmic nature of the electric contacts. The dark and photocurrent increase slightly with increase of SiO2 content and decrease with excess amount of SiO2.