Electronic Structure, Optical and Magnetic Properties of Oxygen-Deficient Gray TiO 2–δ (B).

The gray-colored oxygen-deficient TiO_2–δ(B) nanobelts have been synthesized through a combination of the hydrothermal method followed by an ion exchange process and vacuum annealing. Electron paramagnetic resonance reveals an existence of F-centers in the form of electron-trapped oxygen vacancies within the anionic sublattice of the gray bronze TiO₂ that induces its colouration. The diffuse reflectance spectroscopy showed that the formation of oxygen vacancies into TiO₂(B) significantly increases its absorption intensity in both visible and near infrared ranges. The band gap of TiO₂(B) with anionic defects is equal to 3.03 eV (against 3.24 eV for white TiO₂(B) treated in air). Room temperature ferromagnetism associated with the defects was detected in gray TiO_2–δ(B), thus indicating it belongs it to the class of dilute magnetic oxide semiconductors. It was found that in the low-temperature range (4 K), the magnetic properties of vacuum annealed TiO₂(B) do not differ from those for TiO₂(B) treated in air. We hope that the findings are defined here make a contribution to further progress in fabrication and manufacturing of defective TiO₂-based nanomaterials for catalysis, magnetic applications, batteries, etc. [ABSTRACT FROM AUTHOR]