Controlled Synthesis And Luminescent Properties Of Rare Earth Fluorides Particles

In this dissertation,controlled synthesis of particle morphology and crystal structure,ions doping,structural characterization and fluorescence property of the rare earth fluorides have been systematically investigated.The processing window and synthesis conditions of LnF3 and NaLnF4 compounds in a wide range of lanthanides were clarified,and their morphology,structure and fluorescence property have been discussed.Detailed characterizations of the products were performed by the combined techniques of XRD,FE-SEM,HR-TEM,STEM,SAED and PLE/PL analysis.The following conclusions have been reached:Controlled synthesis of lanthanide(La-Lu and Y)rare earth fluorides was achieved via hydrothermal method using ethylenediaminetetraacetic acid disodium(EDTA-2Na)as a chelating agent.The La-Sm products conform well to the hexagonal LnF3 with particle sizes of?20-40 nm;The Eu-Tb products conform well to the orthorhombic LnF3with particle sizes of?0.3-1 ?m;The Ho-Yb and Y products conform well to the orthorhombic LnF3 with particle sizes of?0.3-1 ?m.Orthorhombic LnF3(Ln=Dy,Tb,Gd,Eu and Sm)can be transformed into hexagonal NaLnF4 via increasing the NH4F/Ln3+molar ratio(R).Monodispersed a-NaYF4:M(M=Ce3+,Eu3+,Tb3+,Er3+,Tm3+,Mn2+,Yb3+/Er3+,Mn2+/Yb3+/Er3+)spheres with a diameter of 300 nm have been successfully synthesized.Longing the reaction time favors the formation of spherical particles with uniform size,while increasing the reaction temperature did not significantly affect the particle size.The products retained the overall crystal structure and morphology of their respective precursors with better crystallization after calcining at 400? for 2 hours,however,obviously agglomerated particles were found at a higher cacination temperature of 600?Under ultraviolet radiation excitation,the a-NaYF4:M(M=Ce3+,Eu3+,Tb3+,Er3+,Tm3+,Mn2+)spheres exhibited blue,red,green,green,blue and green emissions,respectively.Under the 980 nm infrared excitation,the Yb3+/Er3+-doped sample exhibits green emission centered at?524 nm and?541 nm,and the red emission centered at?657 nm.Mn2+doping can realize the enhancement of the 4F9/2?4I15/2 transition of Er3+ more effectively for the particles calcined at 600?.Stable water-soluble cell dye containing dispersed nanoparticles of NaYF4:Eu3+,NaYF4:Tb3+,NaYF4:Mn2+/Yb3+/Er3+was obtained via particle-surface modifying,which was successfully applied in imaging of macrophages and cancer cells.Hexagonal La0.95xGdxF3:0.05Eu3+(x=0-0.2)nanoparticles were prepared via hydrothermal processing.The lattice constant and grain size linearly decrease with increasing the Gd3+content Under excitation at 273 nm and 395 nm,La0.95-xGdxF3:0.05Eu3+nanoparticles exhibited characteristic red emission of Eu3+with strongest one at 591 nm dominated by the 5D0?7F1 transition.Enhanced fluorescence intensity was found at a higher Gd3+content,and the strongest emission was observed at the x value of 0.15.Fluorescence lifetime(?12 ms)and fluorescence color(0.57,0.42)are independent on the Gd3+content.