Controlled-synthesis and up-conversion luminescence of NaYF4: Yb, Er phosphors

Cubic nano-spherical and hexagonal microprismatic NaYF4: Yb, Er up-conversion (UC) phosphors have successfully been synthesized separately through a mild hydrothermal method. The morphology of the NaYF4: Yb, Er crystals can be controlled by adjusting the Ln(3+)/F- ratio in the reaction solution. The efficient UC luminescence can be detected under excitation at 980 nm. Red and green emissions originate from a two-photon mechanism. Factors affecting the phase and morphology of the samples, and their UC luminescence properties are investigated using microscopic and spectroscopic techniques. (c) 2007 Elsevier Ltd. All rights reserved.