S-, N- and C-doped titanium dioxide nanoparticles: Synthesis, characterization and redox charge transfer study

Herein we report on the synthesis and characterization of TiO2 nanomaterials doped with anions like sulfur, carbon and nitrogen. Upon doping, the absorption extends well into the visible region. This shift in the absorption edge is accompanied by a concomitant narrowing of band gap. The resulting anion-doped TiO2 nanomaterials were characterized by XRD, XPS, elemental analysis, EDAX, TEM, UV-DRS, DC conductivity, AC impedance and cyclic voltammetric studies. XPS confirms the presence of the dopants and the elemental analysis determined the amount of dopants in TiO2. Electrochemical characterization was carried out by cyclic voltammetry at pHs 2, 6.5 and 10. As against the response of undoped TiO2, the doped samples show an active electrochemical response indicating an induced charge transfer across the titania/solution interface, thus forming two anodic peaks and a cathodic peak. This interesting and significant observation was understood in terms of band bending due to anion doping as well as to the pH changes in the experimental solutions.