Controlled Synthesis And Research On The Luminescent Properties Of Rare Earth Doped Compound Fluoride Nanomaterials

Rare earth (RE) elements usually exist as trivalent cations due to RE elements easy to lose the electrons of intra-4f, 5d and 6s. With abundant 4f-orbital configurations and the capacity of 4f electrons transition between energy levels, RE3+ ions can exhibit sharp fluorescent emissions. Although rare earth luminescent material is an important and attractive candidate among all kinds of the luminescent materials, people find that direct excitation of RE3+ ions is a relatively inefficient process in practical applications.Howeever, doping RE3+ ions into the matrix lattices can yield desirable luminescence performance. And it can be found that RE3+ ions -doped nanomaterials hold the advantages of lower toxicity, higher chemical stability and so on, compared with lanthanide chelates, quantum dots (QDs), and organic dye molecules.In this regard, we choose the rare earth doped compound fluoride nanomaterials as the basic research object. At present, A variety of sample preparation techniques have been demonstrated to synthesize rare-earth doped compound fluoride nanomaterials. Among these, the thermal decomposition method has been widely used for the synthesis of monodisperse, strong luminescence, small-sized and high quality rare earth doped compound fluoride nanomaterials. In this paper, based on the literature precedents of thermal decomposition, we have made some improvements and modifications for the method. And a series of high-quality LiGdF4, NaGdF4 and KGd2F7 nanomaterials are prepared via the cothermolysis of Gd(CF3COO)3 and CF3COOA ( A= Li+, Na+ ) or Gd(CF3COO)3 and KF in the presence of 1-octadecene as stabilizer and oleic acid as ligand. X-ray power diffraction(XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and Hitachi F-4600 fluorescence spectrophotometer are used for the characterization of the samples.The paper main research content is as follows:(1) Monodisperse, self-assembled a-NaGdF4:Yb0.2Er0.02 nanoparticles and high-resolution structure of ?-NaGdF4:Yb0.2Er0.02 nanoparticles are prepared by tuning the ratio of CF3COONa/Gd(CF3COO)3, the reaction temperature and times. And we also study the crystal phase of nanoparticles, the morphology evolution of self-assembled?-NaGdF4:Yb0.2Er0.02 nanoparticles, and the relative intensity of upconversion luminescence of the samples.(2) The purity tetragonal phase LiGdF4:Yb0.2Er0.02 nanocrystal is prepared via the co-thermolysis of Gd(CF3COO)3 and CF3COOLi. We find that the optimum preparation condition of the tetragonal LiGdF4 nanocrystal is Li/RE=3, t=4 h, T=310?. Under 980 nmexcitation, all the samples have two obvious emission bands. One strong emission band locates at approximately 523 nm and 544 (green upconversion luminescence),another strong emission band locates at approximately 672 nm (red upconversion luminescence).(3) A series of small-sized KGd2F7:Yb0.2Er0.02 nanospheres are synthesized by using a thermal decomposition route. Further, by tuning the ratio of the reaction temperature, KF/Gd(CF3COO)3 and the reaction time, we study the impact on the crystal phase of nanomaterials, the morphology of nanomaterials, and the relative intensity of upconversion luminescence of the samples.