Solvothermal synthesis of monodisperse ultrasmall cubic-structure Ba2YbF7 nanocrystals with intense upconversion

A series of monodisperse ultrasmall Ba2YbF7 nanocrystals with intense upconversion emission were synthesized via a facile solvothermal method by using oleic acid as capping ligands. X-ray diffraction (XRD) and transmission electron microscopy (TEM) assays revealed that the as-synthesized Ba2YbF7 nanocrystals are of cubic structure, rather than the reported tetragonal structure. The cell parameter of the particles is 5.918 Å. The Er3+ or Tm3+ doped Ba2YbF7 nanocrystals with the size of sub-10 nm can give an intense upconversion emission under the 980 nm laser excitation and the upconversion processes were discussed. The Ba2YbF7 nanocrystals show a potential application as a bioimaging agent.

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► Monodisperse Ba2YbF7 nanocrystals of sub-10 nm were synthesized via solvothermal method.
► Ba2YbF7 nanocrystals are of cubic structure instead of tetragonal structure.
► Intense upconversion was obtained in Er3+ or Tm3+ Ba2YbF7 nanocrystals.