title: Bandgap widening of titania through semiconductor support interactions.
abstract: Silica-supported titania powders with 50, 36, 13 and 4 wt% of TiO2 (TiO2-50/SiO2, TiO2-36/SiO2, TiO2-13/SiO2 and TiO2-4/SiO2) were prepared by hydrolysis of TiCl4 in the presence of silica, followed by calcination at 500 degrees C. The formation of Ti-O-Si linkages was confirmed by diffuse reflectance infrared Fourier transform spectroscopy. Atomic force microscopy indicated the presence of titania crystals larger than 15 nm. All supported materials exhibited a blue-shift of the TiO2 absorption edge, which was attributed to an electronic semiconductor support interaction. Bandgap energies of TiO2-50/SiO2, TiO2-36/SiO2, TiO2-13/SiO2 and TiO(2)4/SiO2 were measured to be 3.28, 3.36, 3.40 and 3.42 eV, respectively, as compared to 3.15 eV for unsupported TiO2. From these values, and from the quasi-Fermi level of electrons, a high anodic shift of both the valence and the conduction band was estimated. X-ray photoelectron spectroscopy (XPS) measurements of oxygen 1s- and titanium 2p-binding energies confirmed the anodic shift of the band edges.
authors.affiliation: Institut für Anorganische Chemie II, Universität Erlangen-Nürnberg, 91058 Erlangen (Germany).
authors.forename: Marc
authors.initials: M
authors.lastname: Gärtner
authors.forename: Viatcheslav
authors.initials: V
authors.lastname: Dremov
authors.forename: Paul
authors.initials: P
authors.lastname: Müller
authors.forename: Horst
authors.initials: H
authors.lastname: Kisch