Synthesis of monodisperse spherical Y2O2S:Yb,Ho upconversion nanoparticles

Monodisperse spherical Y2O2S:Yb,Ho upconversion nanoparticles were successfully prepared using a simple homogeneous precipitation method combined with a solid-gas sulfuration technology. The effects of aging time on the particle size and stability of the precursor were investigated, and stable precursor particles were obtained by controlling the aging time. More importantly, it was found that a weak sulfur vapor flow is the key factor to suppress the agglomeration of particles during the sulfuration process. In comparison with the NaYF4:Yb,Er nanocrystals, the Y2O2S:Yb,Ho nanocrystals were found to be more suitable for the application of biological labeling. (c) 2009 Elsevier Ltd. All rights reserved.