Ultraviolet upconversion luminescence in Y2O3:Yb3+,Tm3+ nanocrystals and its application in photocatalysis

Infrared-to-ultraviolet upconversion luminescence agent Y2O3:Yb3+,Tm3+ 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 I-1(6) -> H-3(6) (similar to 297 nm) and D-1(2) -> H-3(6) (similar to 363 nm) emissions from Tm3+ ions were observed at room temperature under 980-nm laser excitation. The change of upconversion emission intensity depending on the Yb3+ concentrations was discussed. The results showed that modest Yb3+ doping could make the upconversion emission of Tm3+ intense, and high Yb3+ 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 TiO2 catalyst doped with Y2O3:Yb3+,Tm3+ was also investigated. It was concluded from the experiment of this study that TiO2/Y2O3:Yb3+,Tm3+ composite had higher photocatalytic activity than pure TiO2 under solar light. This study would make TiO2 utilize sunlight more efficiently and accelerate the practical application of photocatalytic technology in water treatment region.