A simple route to synthesis of carbon doped TiO₂ nanostructured thin film for enhanced visible-light photocatalytic activity

We herein report the pure and carbon doped TiO₂ nanocrystalline thin films synthesized by simple chemical bath deposition technique . The as-deposited films were annealed at 600 °C for 5 h in ambient atmosphere in order to improve crystallinity and structural perfection. The influence of carbon doping on structural, optical, and morphology of thin films was studied by X-ray diffraction (XRD), Fourier Infrared spectra, UV–Vis Spectra, photoluminescence, and atomic force micrograph images. XRD results showed that both pristine and carbon doped films formed mixture of anatase (A) and rutile (R) type phase. The surface roughness has been found to decrease with the increase of the dopant concentration as investigated by atomic force microscopy. The UV–Vis spectra confirmed that incorporation of carbon in the TiO₂ lattice introduced intermediate bands into its narrowed forbidden gap, leading to remarkable red-shifts in the optical absorption edges, together with significantly improved photocatalytic activity of the TiO₂ thin films. The photocatalytic activities of the TiO₂ films were evaluated by degradation of methylene blue rhodamine B in an aqueous solution under ultraviolet light irradiation. Carbon doped TiO₂ film exhibited excellent photocatalytic activities, when compared with undoped TiO₂ film. The improvement mechanism by carbon doping was also discussed.