Synthesis of water dispersible hexagonal-phase NaYF4:Yb, Er nanoparticles with high efficient upconversion...

Yb3+ and EP(3+)-codoped hexagonal-phase NaYF4 nanoparticles are synthesized by a simple, safe, and cost-effective method. The results of X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) show that the as-synthesized nanoparticles are in good accordance with the standard beta-NaYF4 with an average diameter of 60 nm after silica coating. The upconversion luminescence of prepared material under 980 nm excitation is detected, and the luminescence mechanism is discussed.