The structural and optical band gap energy evaluation of nano TiO2 powders by diffuse reflectance spectroscopy prepared via combustion method

Abstract

Nanocrystalline TiO2 powders with different optical band gap have been successfully prepared using solution combustion method starting directly from titanium metal. The emphasis is placed on the role of fuel urea on the variations of optical band gap which is obtained from DRS data in the range of 190–1100 nm. The samples were characterized with XRD, FTIR, FESEM, and DRS. It is shown that the powders calcined at 800 ℃ are predominantly anatase and minor rutile according to XRD results where the crystallite size ranges from 13.2 nm to 22 nm. The size of powders can affect the photo catalytic activity of TiO2 where the surface/ volume ratio determines the available sites for electrons to migrate. The micronized aggregated powders composed of sub-particles in the order of less than 100 nm have no preferred morphology based-on FESEM images. FTIR analysis satisfactorily matched with the standard data. The results of diffuse reflectance spectroscopy (DRS) accompanied with mathematical calculations extracted the values of optical direct band gap of TiO2 powders in the range of 3.53 to 3.6 eV which is in the border of UV and Vis part of electromagnetic radiation. Overall, optical band gap and crystallite size can be controlled by fuel in combustion method.