Bandgap studies on anatase titanium dioxide nanoparticles

Titanium dioxide, predominantly in the anatase phase with an average grain size of 5–10 nm, has been synthesized by the hydrazine method. These nanocrystalline particles show a blue shift in the absorption edge of the diffuse reflectance ultraviolet spectrum of about 10 nm compared to that of commercially available titania. Synthesized samples were characterized by X-ray diffraction and transmission electron microscopy for their structural properties and UV-Vis absorption spectroscopy for the bandgap studies. The absorption spectra show a linear fit for the direct transition. The optical and electrical properties of the samples have been studied and the Arrhenius plots of electrical conductivity both for the as-prepared anatase TiO2 and the one subsequently reduced in hydrogen atmosphere at 673 K show a distinct difference in the activation energy. The hydrogen-annealed sample shows a typical semiconducting behavior whereas the as-prepared sample indicates a phonon contribution to the conductivity around 300 K.