Effect of annealing temperature on structural, optical, and photocatalytic properties of titanium dioxide nanoparticles

Abstract

Titanium dioxide (TiO2) nanoparticles (NPs) were produced by simple sol-gel technique and annealed for 2 h in air. The impact of annealing temperature on the physical, morphological, photocatalytic, and optical properties was studied. X-ray diffraction (XRD) measurements proved that a gradual phase change from anatase to rutile occurred with increased annealing temperature. The crystal structures of the NPs were found to change at different temperatures; anatase phase at 450 °C, mixed-phase (anatase/Rutile) at 550–650 °C, and rutile phase at 750 °C. The rise in the annealing temperature improved the crystallinity of the NPs. The crystal and grain size of the NPs increased with the annealing temperature hence reducing the specific surface area due to the condensed boundaries between subunits of the NPs. As per the Kubelka-Munk equation, the bandgap reduced as the temperature elevated. The photocatalytic activity of the NPs was higher in the anatase/rutile mixed-phase than in the single anatase and rutile phase. Experimental results indicated that annealing temperature could effectively change the properties of the TiO2 NPs.