Effect Of Different Preparation Conditions On Size And Morphology Of NaYF₄ Nanoparticles

In recent years,lanthanide-ion doped upconversion luminescent(UCL)materials have attracted widespread attention.At present,Yb3+ and Er3+ co-doped ?-NaYF4 is one of the most widely studied UCL materials due to its advantages of low phonon energy and high upconversion efficiency.With the development of the preparation of monodisperse nanoparticles technology and mature gradually,based on the ?-NaYF4 luminescent material marking,in the field of biomedical imaging,detection and treatment rendered a great application prospect.At the same time,the research on the infrared capture of solar cells and the anti-counterfeiting field have also been greatly developed.However,it is difficult to achieve mass production due to the small size(<50 nm)of NaYF4 particles produced by existing technology.Either size is large(>1 ?m),and both of these problems seriously hamper its practical application.Therefore,in view of the above situation,this article explores a method for preparing particles of about 200 nm.The detailed results are shown as follow:1.NaYF4:Yb3+,Er3+ UCL materials were prepared by co-precipitation method.The particle size and morphology were adjusted by varing the reaction temperature and time of the nucleation and growth stages.The up-conversion luminescence properties of the sample were analyzed.(1)During the nucleation stage,the samples showed hexagon by changing the reaction times and temperatures.Particle size increases with temperature and reaction time.The sample shows strong green emission when excited by 980 nm laser.The luminescence intensity of the samples improves with the reaction temperature and time in the nucleation stage.(2)During the growth stage,the samples showed hexagon by changing the reaction times and temperatures.The particle size of samples decreases with the increase of reaction temperatures,while increases with the reaction time.The sample shows strong green emission when excited by 980 nm.The luminescence intensity of the sample improves with the increase of the reaction temperature and decrease of the reaction time,respectively.2.Na1-xLixYF4:Yb3+,Er3+ UCL materials were prepared by the co-precipitation method.The particle size and morphology of the samples were studied by varying the concentration of doping Li+ ions(x=0,0.2,0.4,0.5,0.8 mL).Without the doping of Li+ions,the sample presented spherical with a mean size of 24.11 nm.When the concentration of doping Li+ ion reaches a certain value(20%,40%,50%),the morphology of the sample is hexagon prism,the particle size increases with Li+ concentration.The morphology is octahedron when the concentration of doping Li+ ion reaches 80%.Finally,we found that a large particle size was achieved by doping Li+.when the concentration of doping Li+ion reaches 50%,the average particle size particles is 210*290 nm.