Photocatalytic investigations of TiO2–P25 nanocomposite thin films prepared by peroxotitanic acid modified sol–gel method

Abstract

TiO2 thin films and TiO2–P25 nanocomposite thin films were synthesized by sol–gel method utilizing peroxotitanic acid sol (PTA). Films were obtained by three dip coatings of sol on borosilicate glasses. The crystalline size and the variation in phase of thin films were determined through X-ray diffraction. The average crystalline size of the films that was in the range of 42 nm showed a reduction in the value by increasing the rutile content. The surface morphology of the films has been characterized utilizing Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Contact-mode atomic force microscopy (AFM). The results of the morphological investigations were completely coincided with the formation of TiO2–P25 nanocomposite. The optical property of the films has been evaluated by Diffuse Reflection Spectrophotometer (DRS) at the room temperature. The obtained UV–vis spectra for both TiO2 and TiO2–P25 thin films had similar maximum wavelengths. The band gap values for the direct and indirect transitions have been measured for the TiO2 and TiO2–P25 thin films and the results showed negligible variations. The photocatalytical activity of the films was studied by photodegradation of Reactive Red 222 (RR222) under UV irradiation. The results showed that the photocatalytic efficiency of TiO2–P25 nanocomposite thin films had enhanced by the addition of rutile phase which was obviously due to the cooperation of TiO2 and P25 nanoparticles in effective charge transfer process. Additionally, photodegradation rate constant result calculations for the TiO2–P25 nanocomposite thin films can well exhibit the increase in its photocatalytic performance in comparison with TiO2 thin films.