Photoluminescence of TiO2 films co-doped with Tb3+/ Gd3+and energy transfer from TiO_2/Gd~(3+) to Tb~(3+) ions

摘要

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.