Structural and Optical Properties of Sol-Gel Synthesized Tio2 Nanocrystals: Effect of Ni and Cr (Co)Doping

Abstract

Nickel and chromium metal ions have been utilized to dope and co-dope titanium dioxide nanocrystals, thereby broadening the light absorption range of titania into the visible light spectrum. The doped and co-doped TiO2 nanocrystals were prepared using sol-gel techniques, with a varied doping concentration that extended from 0.25 to 10.0 wt.%.These modified materials underwent comprehensive analysis using standard analytical tools such as X-ray diffraction, Raman spectroscopy, BET surface area measurement, Fourier transform infrared spectroscopy, UV-vis diffuse reflectance spectroscopy, and fluorescence spectroscopy.Electronic structural studies of the TiO2, (Ti,Cr)O2, (Ti,Ni)O2, and (Ti,Ni,Cr)O2 crystals using density functional theory indicated a reduction in the band gap width (Eg) of pure TiO2 when doped with transition metals. Specifically, the indirect bandgap values for Ni(10%), Cr(10%) and NiCr(5%+5%) doping were 2.96, 2.83, and 2.7 eV, respectively. Furthermore, the photoluminescence intensity substantially decreased with the integration of transition metal ions in the TiO2 nanocrystals.

Keywords: TiO2, Metal Doping, Co-doping, Band-gap energy, Photoluminescence