Effect of Fe doping on optical properties of TiO2 nanotubes

Abstract

Fe-doped TiO2 nanotubes at different concentrations of Fe are prepared by the combination of sol–gel process and hydrothermal treatment. The effects of Fe doping on the structural and optical properties of TiO2 nanotubes are investigated. The morphology and crystalline structure are identified with transmission electron microscopy, electron diffraction spectra and X-ray diffraction spectra (XRD). UV–vis reflectance spectra and photoluminescence spectra (PL) are employed to study optical properties. Fe doping induces a structural transformation from anatase to rutile. The XRD spectra show peaks of Fe2O3 at the highest concentration of Fe-doped sample. PL spectrum excited at 320 nm shows the presence of surface oxygen vacancies and self-trapped excitons in Fe-doped and undoped TiO2 nanotubes. The emission due to oxygen vacancies decreases with increasing dopants concentration. The PL spectra of Fe-doped TiO2 nanotubes exhibit luminescence bands at about 526 nm, which are absent in undoped sample. Direct transition peak in the PL spectra of Fe-doped TiO2 nanotubes has a red shift as compared to the undoped one. Band gap energy is at its lowest at the highest concentration of Fe-doped TiO2 nanotubes.