Preparation And Properties Of Rare Earth Doped Fluoride Nano-luminescent Materials

In recent years, with the rapid development of science and technology, therare earth ions doped up-conversion luminescence materials have been widely usedin the short-wavelength solid state lasers, optoelectronic devices, medical diagnostics,biological labels, silicon solar cells and many other fields because of their numerousadvantages.Based on the n-butanol-water-oleic acid system, different rare earth ions dopedfluoride microcrystals and nanocrystals were prepared via a simple and mildhydrothermal method. The crystal phase and morphology of the rare earth ionsdoped fluoride luminescent materials were effected by the experimental condition, itwas studied by X-ray Diffraction(XRD), scanning electron microscopy(SEM),transmission electron microscopy(TEM), fluorescence spectrum and so on, and thepossible up-conversion mechanism was also proposed and discussed.Er3+/Yb3+codoped NaYF4microcrystals were prepared. The results show thatthe transformation from cubic phase to hexagonal phase was sped up remarkablywhen Zr4+ions were introduced into the reaction system; the crystallinity and size ofthe product became higher and larger when prolong time; the greater amount ofNH4F was conducive to generate the rules of morphology β-NaYF4microcrystals;the higher reaction temperature was given, the hexagonal NaYF4microcrystals wereappeared; hexagonal NaYF4microcrystals that had rules of morphology and highercrystallinity could be obtained when the amount of ethanol was greater than or equalto15ml. Under980nm excitation, intense green and red up-conversion luminescencewas observed in Er3+/Yb3+codoped NaYF4microcrystals due to their crystalstructure of hexagonal phase, large grain size and high crystallinity, and largeabsorption coefficients of Yb3+ions around980nm made the as-synthesized NaYF4microcrystals exhibiting potential applications in the fields of amorphous siliconsolar cells and dye-sensitized solar cells.Tm3+/Yb3+codoped and Eu3+single doped BaYF5nanocrystals were prepared.The experiments found that when the pH value of the system was7, adopting NH4F as fluorine source and without heat treatment in the late, the reaction could achieverodlike BaYF5nanocrystals which have tetragonal phase structure and strongup-conversion luminescence under220℃for24hours. Particllarly, under980nmexcitation, intense near-infrared up-conversion luminescence was observed inTm3+/Yb3+codoped BaYF5nanocrystals, and that showed important applicationprospect in the field of biological labels and medical imaging. The change of Eu3+ions’ concentration had very little impact on the crystalline phase of BaYF5nanocrystals, but the excitation spectra and emission spectra of the samplesincreased along with the augment of Eu3+ions’ concentration.