Luminescence Properties And Fluorescence Stabilization Of Rare Earth Ions Doped Upconversion Nanoparticles

With the development of precision medical,upconversion nanoparticles are used in analytical chemistry more and more widely due to its unique advantages.In this paper,hydrophilic upconversion nanoparticles with core-shell structure were fabricated through a solvothermal method.Luminescence which is excited by 808 nm can be studied by tuning ratio of core and shell components.Lipophilic upconversion nanoparticles were synthesized through coprecipitation of high temperature.Via a simple surface treatment,particles were transfromed from oil solubility into water solubility.As a new surfactant,the stability of alendronic acid was in-depth exploration.The main research content and results are as follows:Using ethylene glycol（EG）as solvent and polyethyleneimine（PEI）as surfactant,upconversion nanoparticles（UCNPs）with polycrystalline shell structure have been synthesized via solvothermal method.The polycrystalline shell is confirmed and calculated by HAADF,HRTEM and size distribution from TEM.Shell thickness is readily tuned by control the amount of reactant.When the polycrystalline shell thickness is 1.7nm,the upconversion luminescence intensity reaches the maximum which is different from the situation of single crystal shell.The possible reason is that a large number of grain boundaries in the polycrystalline shell lead to a serious loss of energy transfer in the Yb-Yb long distance energy migration.Hexageonal-phase upconversion nanoparticles were prepared through coprecipitation of high temperature.In the course of study,we chose phosphate buffer（PBS）as simulated biological fluids.And then how upconversion luminescent properties of UCNPs changed was under research which was modificated with different ligands.We found that alendronic acid which is bisphosphonate can prevent UCNPs luminescence from being quenched effectively.Afterwards single phosphine ligands and SiO₂ layer come after it.At last other ligands without phosphines were in the third echlon,and only slightly superior to bare UCNPs.