Ultraviolet upconversion luminescence in Y_2O_3:Yb ~(3+),Tm~(3+) nanocrystals and its application in photocatalysis

摘要

Infrared-to-ultraviolet upconversion luminescence agent Y_2O _3:Yb~(3+),Tm~(3+) was prepared by a combustion method using citrate as a fuel/reductant. The prepared sample was characterized by X-ray diffraction, SEM, and fluorescence spectrophotometer. Two unusual ~1I_6 → ~3H_6 (~297 nm) and ~1D_2 → ~3H_6 (~363 nm) emissions from Tm~(3+) ions were observed at room temperature under 980-nm laser excitation. The change of upconversion emission intensity depending on the Yb~(3+) concentrations was discussed. The results showed that modest Yb3+ doping could make the upconversion emission of Tm~(3+) intense, and high Yb~(3+) concentrations might lead to fluorescence quenching. Moreover, the influence of ultraviolet upconversion luminescence on the photodegradation of methyl orange aqueous solution under solar light irradiation in the presence of TiO_2 catalyst doped with Y _2O_3:Yb~(3+),Tm~(3+) was also investigated. It was concluded from the experiment of this study that TiO_2/Y _2O_3:Yb~(3+),Tm~(3+) composite had higher photocatalytic activity than pure TiO_2 under solar light. This study would make TiO_2 utilize sunlight more efficiently and accelerate the practical application of photocatalytic technology in water treatment region.