| The up-conversion luminescence phenomenon has enormous potential applications in many new areas. Therefore, the research of experiment and theory of nano-sized upconversion luminescence materials has become one of the hotspots in the research fields of advanced materials nowadays. It is the aim to find a suitable oxide as a doped matrix for rare-earth ions to get high up-conversion efficiency. The up-conversion luminescence properties of rare-earth ions were discussed under a 980nm LD excitation under different annealed temperature, concentration and so on in TiO2 nanocrystals matrix. The up-conversion mechanisms of the TiO2:Er3+, TiO2:Er3+/Yb3+ and TiO2:Tm3+/Yb3+ were investigated. The results as bellow:1. Green and red emissions at 525nm, 548nm and 660nm were obtained in TiO2:Er3+ and TiO2:Er3+/Yb3+ nano-crystallite. Blue and red emissions at 476nm and 651nm, 694nm were obtained in Tm3+/Yb3+ co-doped TiO2 nano-crystallite. The structure and size of TiO2 nanocrystals were changed after doping rare-earth.2. Because of the special energy level of Yb3+, it can sensitize Er3+ and Tm3+. The luminescence intensity in Er3+/Yb3+ and Tm3+/Yb3+ co-doped TiO2 samples are much stronger than those without Yb3+ ions.3. In Er3+-doped TiO2 nanocrystal, the luminescence intensity increases and then obviously decreases with increasing heat-treatment temperature; In the Yb3+/Tm3+-codoped TiO2 nanocrystal, the luminescence intensity increases with increasing heat-treatment temperature.4. In Li+/Yb3+/Tm3+-tri-doped TiO2 nanocrystal, the up-conversion luminescence intensity is enhanced remarkably after Li+ doping. When Li+ doping concentration is 3.0mol%, up-conversion luminescence intensity reaches maximum.5. According to the relation between the up-conversion intensities and the power pump, the up-conversion luminescences mechanism of Er3+,Er3+/Yb3+ and Tm3+/Yb3+ in TiO2 nanocrystals are attributed to two-photon absorption up-conversion process.
|
PDF Full Text Request