  The local structures and optical absorption characteristic of Fe doped TiO2
nanoparticles synthesized by the sol-gel method were characterized by X-ray
Diffraction (XRD), X-ray absorption fine structure spectroscopy (XAFS) and
UV-Vis absorption spectroscopy (UV-Vis). XRD patterns show that all Fe-doped
TiO2 samples have the characteristic anatase structure. Accurate Fe and Ti
K-edge EXAFS analysis further reveal that all Fe atoms replace Ti atoms in the
anatase lattice. The analysis of UV-Vis data shows a red shift to the visible
range. According to the above results, we claim that substitutional Fe atoms
lead to the formation of structural defects and new intermediate energy levels
appear, narrowing the band gap and extending the optical absorption edge
towards the visible region.
