Abstract
La2O2S:Er3+,Yb3+ nanocrystalline up-converting phosphors were synthesized by a combustion method at low temperature, using ethanol as pre-ignition fuel and thioacetamide as sulfurizing agent and organic fuel. The phosphors were characterized by powder X-ray diffractometry, scanning electron microscopy, UV/Vis/NIR spectroscopy and fluorescence spectroscopy. Pure and well-crystallized La2O2S:Er3+,Yb3+ nanoparticles, of the order of 50–200nm, are obtained after a post-treatment in a H2S/N2 flow for 2h at 1000°C. The efficient energy transfer from Yb3+ to Er3+ results in a strong up-conversion upon excitation at 980nm. The emission spectra show the intense green emissions corresponding to the (2H11/2, 4S3/2)→4I15/2 transitions and a red emission corresponding to the 4F9/2→4I15/2 transition. Additionally, within the investigated co-doping concentrations, no significant concentration quenching effect and back energy transfer from Er3+ to Yb3+ were evidenced. This research highlights the influence of the sulfurization treatment on the purity/crystallinity/morphology of the nanocrystals and the luminescence efficiency.
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