Preparation And Properties Of Rare Earth Fluoride And Composite

In this thesis,high quality?monodisperse,uniform morphology,and uniform size?and strong upconversion luminescence core nanoparticles NaYF₄:20%Yb³⁺,2%Er³⁺have been successfully synthesized via the thermal decomposition method under different reaction time,different reaction temperature and different oleic acid content.The optimum preparation conditions of NaYF₄:20%Yb³⁺,2%Er³⁺nanoparticles with the strongest up-conversion luminescence properties have been characterized by XRD,SEM and photoluminescence,which were as follows:reaction time was 75 min;reaction temperature was 310°C;the amount of oleic acid was 3mL.Then a series of core-active shell NaYF₄:20%Yb³⁺,2%Er³⁺@NaGdF₄:xYb³⁺?x=0.1,0.2,0.3,0.4,0.5?composite nanoparticles were synthesized by epitaxial growth method.The up-conversion luminescence intensity is 6 times that of the core under the condition that the doping concentration of Yb³⁺is 40%.The up-conversion luminescence of NaYF₄:20%Yb³⁺,2%Er³⁺@NaYF₄ prepared by growing an inert shell outside the core nanoparticles is 32 times that of the core.The core-active shell-inert shell nanoparticles NaYF₄:20%Yb³⁺,2%Er³⁺@NaGdF₄:40%Yb³⁺@NaYF₄ obtained by continuous epitaxial growth method possess the highest up-conversion strength,which is 76 times that of the core.Ultimately,the NaYF₄:20%Yb³⁺,2%Er³⁺@NaGdF₄:40%Yb³⁺@NaYF₄@CdS nanoparticles with the excellent catalytic activity were synthesized by the esterification reaction of mercaptoethanol and thioglycolicacid.First,under near-infrared illumination the degradation rate of the RhB is 53.5%for 140min.Second,under simulated sunlight,the degradation rate of rhodamine B was 86%for 55 min.The result is 1.54 times that of the pure CdS.Then,after 5 cycles of experiments,the degradation rate is still higher than 80%,which indicates that the sample has good stability and recyclability.Through the photocatalytic active substance test,it is known that·O₂^-plays a major role and h⁺plays a minor role.In addition,the possible catalytic mechanism was proposed.