Synthesis, Characterization And Properties Of YF₃Micro/Nano—structures

Rare earth fluoride micro/nano–materials have a wide application aspects in thefields of optics, biological marker, sensors and security with the excellent propertiessuch as strong fluorescence intensity, long fluorescence lifetime, relatively stableoptical and chemical properties and non–toxic, which caused the researchers greatinterest. Recent years, carrying out research work in this area has become a hot anddifficult topic with a good theoretical and practical value. This paper uses themicrowave method, solvothermal and low temperature reaction methods successfullyfabricated a good dispersion of rare earth fluoride micro/nano–materials, structure andperformance characterizations of the product were obtained by using a variety of testtechniques, the fluorescence properties and luminescence mechanism were alsoexplored.The main contents of this thesis are included:（1） Microwave–Assisted Synthesis, Characterization and Luminescent Propertiesof water–soluble YF₃and YF₃:Ln³⁺nanocrystals.Water–soluble YF₃and lanthanide–doped YF₃nanocrystals have been preparedemploying a simple microwave–assisted approach carried out in ethanol solution in15min. The obtained nanocrystals are ascribed to orthorhombic structure YF₃.Scanning electronic microscopy （SEM） and transmission electron microscopy （TEM）results demonstrate that the as–prepared nanocrystals are with diameters of about6–10nm and these nanoparticles aggregate to form bigger assemblies with diametersof about40–60nm. Results demonstrate that the as–prepared YF₃nanocrystals can bewell dispersed in water, forming a stable and transparent colloidal solution.Water–soluble Ce³⁺, Tb³⁺and Eu³⁺doped YF₃nanocrystals have also been preparedand their photoluminescence properties have been investigated. Results show that theluminescence lifetime of the Eu³⁺doped YF₃powder sample and solution sample is8.6ms and6.8ms, respectively. Due to the long decay time of the products, it haspotential application in biolabeling and many other applications may be found.（2） Uniform YF₃nanorods: Synthesis, luminescent properties and cytotoxicitystudy.Uniform YF₃nanorods composed of nanoparticles were successfully preparedvia a facile solvothermal method with ethanol as solvent and tetrabutyl ammoniumfluoride （TBAF） as fluorine source. The products were characterized with powder X–ray diffraction （XRD）, scanning electron microscopy （SEM） and transmissionelectron microscopy （TEM）. The nanorods were with diameters of ca.60nm andlengths ranging from200to350nm. Eu³⁺and Tb³⁺doped YF₃nanorods were alsoprepared and their photoluminescence properties were investigated. Cytotoxicitystudy revealed that these YF₃based nanorods were biocompatible.（3） Ionic liquid-assisted synthesis YF₃microparticles at low-temperatureOn the basis of successful preparation of the above YF₃nanorods, we changedthe reaction conditions of the precursor, the morphology of rice–like YF₃microparticles composed of particles were synthesized by tetrabutyl ammoniumfluoride ammonia and rare earth nitrates on condition that solid state reaction at lowtemperatures. During the reactions, TBAF acts as a fluorine source, ionic liquids （ILs）and templates. The crystal structure, morphology of the as–prepared YF₃crystals werecharacterized by X–ray powder diffraction （XRD） and scanning electron microscopy（SEM）. Results revealed that highly uniform microparticles about250nm in lengthswith150nm in widths were obtained. This method was also employed to thepreparation of Eu³⁺–doped YF₃and Tb³⁺–doped YF₃. The luminescent properties ofthe synthesized materials were also evaluated.