Preparation And Luminescent Properties Of Three Typical Rare Earth Doped Micro/Nano Fluoride Upconversion Materials

The lanthanide-doped upconversion luminescent material is an inorganic crystalline material which can convert low-energy near-infrared light into high-energy ultraviolet or visible light.More attentions have been paid to up-conversion?UC?luminescence nanoparticles?UCNPs?due to their its unique optical properties and potential applications in a broad range of fields,i.e.three dimensional display,temperature sensors,solid-state lasers,biomedical imaging.However,the lower upconversion luminescence efficiency of these materials limits their application in many fields.Compared to oxide,Fluoride has low phonon energy.Therefore,reduced the quenching of the excited state of rare earth ions.In this thesis,three typical fluoride-upconverting micro/nano crystals BaLiF₃,NaLuF₄ and NaGdF₄ doped with rare earths are studied to improve the up-conversion luminescence intensity as the entry point.Thereby promoting the application of upconversion nanocrystals in multicolor output,temperature sensing,optical heating,etc.The main research contents are as follows:1.A series of xmol%Yb,1mol%Ho/1mol%Er/1mol%Tm co-doped BaLiF₃crystallites were synthesized by wet chemistry.The effects of different reaction conditions on the phase,morphology and luminescence properties of the matrix were investigated.The dissolution process and recrystallization of samples at different pH values and their effects on morphology were discussed.The possible growth mechanism was also illustrated.Then we studied the effect of Yb³⁺concentration on upconversion luminescence of BaLiF₃:xmol%Yb,1mol%Ho.At last,the mechanism of Li-doped enhanced up-conversion luminescence of Er³⁺-Yb³⁺co-doped BaLiF₃crystallites was investigated.These studies provide a theoretical basis for the application of BaLiF₃ crystallites in the field of micro-devices for multi-color emission and biological applications.2.The effects of Li⁺doping on the phase,morphology and size of NaLuF₄:Ln?Ln=Yb,Ho,Er and Tm?nano/micro crystals were investigated.And the two paths of Gd³⁺ions doping and optimization of preparing technology were explored to synthesis a good single-phase sample of NaLuF₄:10mol%Yb,1mol%Ho,xmol%Li?0?x?20?.Then we discussed the dependence of the luminescence intensityof NaLuF₄:10mol%Yb,1mol%Tm,xmol%Li?0?x?20?on temperature,and the mechanism of abnormally enhanced red?695 nm?emission was investigated.In Li⁺-doped NaLuF₄:10mol%Yb,1mol%Er,xmol%Li?0?x?18?powders,the occupancy of the site and the effect on the morphology were investigated.In order to improve the upconversion luminescence efficiency of rare earth ions,the mechanism of Li⁺doping concentration effect on the emission intensity were explored.3.The effects of Mn²⁺ion doping on the morphology,luminescence,temperature sensing and optical heating of the matrix were investigated.It mainly includes NaGdF₄:20mol%Yb,1mol%Tm,xmol%Mn,NaGdF₄:20mol%Yb,1mol%Er,xmol%Mn and NaGdF₄:20mol%Yb,1mol%Ho,xmol%Mn.The emission color covers an area from blue to near-infrared.The mechanism of energy transfer between Mn²⁺and RE³⁺was characterized by a systematic study on the enhanced upconversion luminescence properties of Mn²⁺doped reinforcement.The effect of Mn²⁺on the upconversion luminescence properties of these three materials was systematically investigated.At the same time,we explored the mechanism of the energy transfer between Mn²⁺and RE³⁺.Studying the FIR variation and optical heating performance caused by excitation power provides effective guidance for the application of up-conversion nanoparticles in spectral control,multi-color output and temperature sensing.