The Preparation And Upconversion Luminescent Properties Of NaYF₄Micro/Nanocrystals Doped With Rare-earth Ions

In recent years, the rare earth ions doped up-conversionluminescence mic-ro/nanocrystals have been widely used in some fields such as laseranti-counterfeit, three-dimensional displays, silicon solar cells and biomedicine due totheir unique physical and chemical properties and special upconversion luminescenceproperties. However, the luminescence efficiency is still low in current upconversionmaterials，and how to enhance upconversion luminescence efficiency is a key issuefaced by reserachers. In addition, the morphology and size is also an importantinfluence factor for the application of upconversion luminescence materials, so how torealize the controllable growth of micro/nano-sized upconversion materials is alsourgent problem for researchers. To solve these problems, we prepared rare-earth ionsdoped NaYF4micro/nanocrystals by hydrothermal methods in this paper, andinvestigeted the dependences of the microstructures, morphologies and upconversionluminescence properties on growth growth conditions.Yb3+/Er3+co-doped NaYF4micro/nanocrystals were prepared by hydrother-malmethods.The influence of the concentration of F-ions, reaction time and Yb3+ionsdoped concentration on the crystalline phase, size and morphology of the sampleswere investigated. With980nm infrared laser as excitation source, the green and redupconversion emissions were obtained in the samples. The upconversionluminescence intensities were investigated for the obtained sampes corresponding todifferent F-consentration and Yb3+ions concentration, and the luminescencemechanisms were discussed.Cr3+/Yb3+/Er3+co-doped NaYF4microcrystals were fabricated by hydrothermalmethod, and the inflenence of Cr3+concentration on the morphology of themicrocrystals was discussed. By Cr3+introduction, the enhanced effect ofupconversion luminescence was observed in Yb3+/Er3+co-doped NaYF4microcrystals.The green and red emission intensity of the sample corresponding to30% Cr3+concentration in source materials respectively enhanced by30times and20timescompared to the sample without Cr3+introduction, and the luminescence enhancementmechanism was explained.Tm3+/Yb3+and Ho3+/Yb3+co-doped NaYF4microcrystals were obtained byhydrothermal methods. The strong blue and green upconversion emissions wererespectively obtained in two materials.The upconversion luminescence properties ofTm3+and Ho3+corresponding to different Yb3+doping concentration wereinvestigated, the luminescence mechanisms were discussed.