CONTROLLED SYNTHESIS OF BRIGHT AND COMPATIBLE LANTHANIDE-DOPED UPCONVERTING NANOCRYSTALS

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Phosphorescent upconverting, lanthanide-doped, hexagonal, B-phase NaYF4 nanocrystals, down to 5 nm in diameter are disclosed. The size of the nanocrystais was modulated by varying the concentration of basic surfactants, Y3+ : F- ratio, and reaction temperature variables that also affected their crystalline phase. A method of making phosphorescent upconverting sub-10 nm lanthanide-doped hexagonal B-phase NaYF4 nanocrystals includes preparing a stock solution of rare-earth oleates for Vb, Er doped NaYF4 by addition of yttrium chloride, ytterbium chloride and erbium chloride to a flask; adding oleic acid and 1-octadecene to the flask; stirring the suspension, heating, cooling the stock solution to room temperature, mixing solid sodium oleate, anhydrous NH4F, and the rare-earth oleate stock solution and adding oleylamine and additional 1-octadecene to form a mixture in the flask, further heating the mixture, cooling the mixture and adding ethanol to precipitate the nanocrystals.