Rare Earth Ions Co-doped Gd ₂ O _{Research Upconversion Luminescence Properties Of 3} Nanotubes

Rare earth ions have been used to prepare for the up-conyersion fluorescent materials due to a wealth of energy levels and stable chemical properties. With the improvement in research on up-conversion fluorescence materials, these materials have many potential properties and have widespread application prosects in infrared biological detection, solid-state laser, light storage device, three-dimensional display etc. The main contents and results of this paper are summarized as follows:A series of Ho3+, Ho3+/Yb3+, Tm3+, Tm3+/Yb3+, Ho3+/Yb3+/Tm3+and Ho3+/Yb3+/Li+co-doped nano materials are prepared respectively by Sol-Gel method. The micro-structure of nanotubes is confirmed by the XRD and SEM techniques. The formation of grains at different annealing temperatures is studied. The up-conversion fluorescence spectra of rare earth ions Ho3+and Tm3+are observed. The results show that the green-light emission range within520nm-580nm is originated from Ho3+(5F4/5S2â†'5I8) radiation, the red-light emission range within630nm-670nmis originated from Ho3+(5F5â†'5I8), and the blue emission range with470nm-500nm is due to Tm3+(1G4â†'3H6). Depending on the change of doping concentration, the intensity of red, blue and green light can be adjusted. According to the rare earth ions energy level matching conditions, the relationship between fluorescence excitation spectra and pump light power, the up-conversion luminescence mechanism can be obtained. The results show that red and green emissions are mainly two-photon process, while the blue emission is mainly three-photon process. Meanwhile, we find the direct sensitization up-conversion between Yb3+and Tm3+and analyze the up-conversion luminescence mechanism of Ho3+/Yb3+/Tm3+co-doped Gd2O3system. Above all, Tm3+has the quenching effect to Ho3+due to the cross relaxation process. The results show that the intensity of green light is reduced, while the blue one is effectively improved. The influence of Li+to the Ho3+/Yb3+co-doped Gd2O3system is also analysised and by incorporating the right amount of Li+, the fluorescence intensity is enhanced almost an order of magnitude. We conclude that Li+can improve the luminescence emission effectively.