Preparation and characterization of hollow TiO2 nanospheres: The effect of Fe3+ doping on their microstructure and electronic structure

Hollow Fe-doped TiO2 spheres with various Fe dopant concentrations, 0.25, 0.50 and 1.0 wt%, were synthesized via a hydrothermal method using carbon spheres as templates. The prepared samples were calcined in air at temperatures of 500 and 550 degrees C for 3 h and characterized using XRD, SEM, TEM, SAED, EDX, XPS and UV-vis spectroscopy. The analytical results showed that the presence of a very low concentration of Fe3+ incorporated into hollow nanoporous TiO2 spheres inhibited the growth of nanocrystals as well as the anatase to ruffle phase transformation inside the anatase TiO2 lattice. Doping with 1.0 wt% Fe3+ resulted in a reduction of the TiO2 sphere diameter from 205.71 +/- 25.29 nm to 68.70 +/- 7.07 nm. The optical energy gap of the samples was determined from UV-Vis absorption spectra. The results showed that the absorption edge of TiO2@Fe was shifted toward the visible light region with increased Fe content.