Two-phase solvothermal synthesis of rare-earth doped NaYF 4 upconversion fluorescent nanocrystals

Abstract

The synthesis, characterization, and fluorescent spectra of rare-earth doped NaYF 4 upconversion nanocrystals are introduced in this paper. The nanocrystals were synthesized in the water-ethanol-oleic acid system via a two-phase solvothermal approach, by using rare-earth stearate as the precursor. The as-prepared nanocrystals were of hexagonal phase, strong UC fluorescent intensity, with an average size of about 25 nm, which have been characterized by TEM, SAED, powder XRD, and luminescence spectroscopy. The possible mechanism of this synthesis that the nucleation and growth of nanocrystals occurred at the solid–liquid interface was also discussed. The nanocrystals are hydrophilic, and expected to fulfil the demand for biological applications via further modification.