Visible Region Response of Cobalt Doped TiO2via Sol Gel Technique

Abstract

TiO2 nanoparticles were prepared via sol gel technique, and then doped with cobalt ions to form TiO2 doped cobalt sol. Thin films were prepared from this sol using dip coating method and underwent calcination at a temperature of 550°C.The films were characterized by UV–Vis spectroscopy, X-ray diffraction (XRD), and atomic force microscopy (AFM).The UV–Vis.Absorption spectra show a red shift, which indicates that TiO2 doped cobalt will responds to the visible region of spectrum rather than UV- region for pure TiO2.1-Introduction Titanium dioxide (TiO2) is one of the most interesting n-typesemiconductor materials due to its wide applications such as self- cleaning surfaces, antifogging function, antibacterial function, and decomposition of pollutants [1,2].TiO2 has two main drawbacks it has a photocatalytic activity under UV-light irradiation only since its energy gap is wide (3.2 eV) for anatase phase, (λ= 387nm), and UV forms less than 5% ofsolar spectrum while the dominantspectral region of solar spectrum is visible.Another drawback is the fast electron–hole recombination. To overcome these limitations, several efforts have been made by modifying the surface or bulk properties of TiO2 through doping with metals and non-metals in order to reduce the band gap and delay electron–hole recombination[3]. In this work, cobalt doped TiO2was studied since there are a few published papers on this transition metal. Cobalt doped TiO2 sol was achieved by sol gel technique, and thin films of this sol were prepared using dip coating method.