Luminescence enhancement of NaGdF4:Yb,Er,Li and its improving effect on the photocatalytic degradation of ZnIn2S4

Abstract

In order to enhance the performance of NaGdF₄:18%Yb,2%Er upconversion luminescence, alkali metal ion Li⁺ doping modification was carried out, and at the same time, in order for the energy of upconversion luminescence to be efficiently utilized in conjunction with ZnIn₂S₄ photocatalysts, to improve the degradation rate of the photocatalysts in the full-spectrum and near-infrared light. We synthesized alkali metal ion Li⁺-modified NaGdF₄:18%Yb,2%Er upconversion luminescent materials with different doping amounts by hydrothermal method, and selected the Li⁺ doping amount with optimal luminescence performance, and the results showed that the luminescence intensity was increased by a factor of 2.3 and the decay time was prolonged by 0.29 ms. In order to solve the problem that it is difficult to realize the light response in the full spectrum by itself photocatalyst, it is combined with upconversion materials to realize the effective transfer of upconversion luminescence energy. A composite photocatalytic system of NaGdF₄:18%Yb,2%Er,10%Li and ZnIn₂S₄ was prepared, and the degradation rate of the content of NaGdF₄:18%Yb,2%Er,10%Li was investigated for the reaction of 50 mg/L MB under near-infrared light(NIR) and full spectrum for 120 min. The composite photocatalysts coated with different contents of ZnIn₂S₄ were further investigated. It was shown that the composite photocatalysts with 10 % NaGdF₄:18 % Yb,2 % Er,10 % Li and 1 % ZnIn₂S₄ had the best degradation rate, and the degradation rates of MB in the NIR and the full spectrum were enhanced by 36 % and 32 %, respectively. It is shown that Li ⁺ doping alters the local symmetry of the crystal field of NaGdF₄:18%Yb,2%Er to enhance the upconversion luminescence and photocatalytic performance, and the essence of the enhanced photocatalytic performance lies in the fact that the energy of the upconversion luminescent material in NaGdF₄:18%Yb,2%Er,10%Li@ZnIn₂S₄ is transferred to the photocatalyst, which promotes photocatalyst carrier motion.