Tuning the band gap of TiO2 by tungsten doping for efficient UV and visible photodegradation of Congo red dye.

Tungsten-doped TiO2 (W@TiO2) nanoparticles, with different percentages of atomic tungsten dopant levels (range of 0 to 6 mol%) have been synthesized by the sol-gel method and characterized by UV-Visible spectroscopy, XRD, SEM, EDX, ICP-OES and XPS analysis. By means of UV-Vis spectroscopy, it has been observed that with 6 mol% tungsten doping the wavelength range of excitation of TiO2 has extended to the visible portion of spectrum. Therefore, we evaluated the photocatalytic activity of W@TiO2 catalysts for the degradation of Congo red dye under varying experimental parameters such as dopant concentration, catalyst dosage, dye concentrations and pH. Moreover, 6 mol% W@TiO2 catalyst was deposited on a glass substrate to form thin film using spin coating technique in order to make the photocatalyst effortlessly reusable with approximately same efficiency. The results compared with standard titania, Degussa P25 both in UV- and visible light, suggest that 6 mol% W@TiO2 can be a cost-effective choice for visible light induced photocatalytic degradation of Congo red dye.