Synthesis and Characterization of NaYF4:Yb3+:Er3+/NaYF4 Upconversion Nanophosphors

Abstract

The NaYF4:Yb3+:Er3+/NaYF4 upconversion nanophosphors (UCNPs) containing ions of rare-earth elements with a core/shell structure were synthesized solvothermally, and their photoluminescent properties were analyzed depending on the size of nanoparticles and preparative synthesis conditions. We showed that the intensity and lifetime of photoluminescence of the upconversion nanoparticles depend on the intensity of laser excitation, the size of the nanoparticles, and the presence of an inert shell. When an inert shell is formed on the surface of NaYF4:Yb3+:Er3+ nanoparticles, the conversion coefficient of visible and near-IR radiation in different spectral regions can increase by an order of magnitude owing to the shielding of luminescent centers from nonradiative losses at surface defects.