Photoluminescence of TiO 2 films co-doped with Tb 3+/ Gd 3+and energy transfer from TiO 2/Gd 3+ to Tb 3+ ions

Abstract

Nanometer TiO 2 thin films doped with different concentration of Tb were prepared by sol–gel method and characterized by X-ray diffraction (XRD), thermogravimetry–differential thermal analysis (TG-DTA), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. XRD results show preferentially oriented (101) anatase films. TEM image indicates that the TiO 2 films consist of TiO 2 grains with diameter about 15 nm. Under room temperature, strong visible luminescence of Tb 3+ ions due to intra-4f shell transitions are obtained and the PL intensity is found to have a well matching relation with the doping concentration of Tb 3+ ions. Concentration quenching of PL occurs when Tb 3+ concentration exceeds a certain value (9.2 mol%). Furthermore, the luminescence intensity is improved obviously after co-doping with Gd 3+ ions because of the sensitization effects of Gd 3+ ions to Tb 3+ ions in TiO 2 system. The energy transfer mechanism from TiO 2 and Gd 3+ ions to Tb 3+ ions was proposed.