Optical properties of in situ doped and undoped titania nanocatalysts and doped titania sol–gel nanofilms

In this paper we present spectroscopic properties of doped and undoped titanium dioxide (TiO2) as nanofilms prepared by the sol–gel process with rhodamine 6G doping and studied by photoacoustic absorption, excitation and emission spectroscopy. The absorption spectra of TiO2 thin films doped with rhodamine 6G at very low concentration during their preparation show two absorption bands, one at 2.3 eVattributed to molecular dimmer formation, which is responsible for the fluorescence quenching of the sample and the other at 3.0 eVattributed to TiO2 absorption, which subsequently yields a strong emission band at 600 nm. The electronic band structure and optical properties of the rutile phase of TiO2 are calculated employing a fully relativistic, full-potential, linearized, augmented plane-wave (FPLAPW) method within the local density approximation (LDA). Comparison of this calculation with experimental data for TiO2 films prepared for undoped sol–gels and by sputtering is performed. # 2006 Elsevier B.V. All rights reserved.