Morphology Dependent Luminescence Properties of Co Doped TiO₂ Nanostructures

Abstract

One dimensional (1D) anatase Co doped TiO2 nanostructures such as nanorods, nanowires, and nanotubes were synthesized by a simple solvothermal method using CoCl2·6H2O as the cobalt source. The effect of the different solvents on the crystal structures, morphologies, and sizes of the Co doped 1D nanostructures was investigated. The doping concentration of the samples primarily depends on the solvents. The X-ray photoelectron spectroscopy studies clearly showed that the Co was incorporated into the TiO2 lattice as Co2+ and oxygen vacancies were created due to the substitution of the Ti4+ ions by Co2+ ions. Optical absorption measurements showed additional absorption bands that are due to the ligand field transitions, 4T1g(4F) → 4T1g(4P) of Co2+ and also due to the transitions from different trap states related to the oxygen vacancies. The effects of the doping concentration on the defect structures and oxygen vacancies of the 1D nanostructures were mainly investigated using steady state photoluminescence (PL) and PL decay.