Combustion synthesis and up-conversion luminescence of La2O2S:Er3+,Yb3+ nanophosphors

• La2O2Er3+, Yb3+ up-converter nanophosphors were prepared by combustion synthesis.
• The synthesis method results in phosphor nanoparticles of the order of 50–200 nm.
• Energy transfer from Yb3+ to Er3+ results in a strong UPL upon excitation at 980 nm.
• No concentration quenching effect and back energy transfer were evidenced.
• We report the importance of the post-treatment in a H2S/N2 flow on UPL efficiency.

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 50–200 nm, are obtained after a post-treatment in a H2S/N2 flow for 2 h at 1000 °C. The efficient energy transfer from Yb3+ to Er3+ results in a strong up-conversion upon excitation at 980 nm. 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.

Up-conversion luminescence of La2O2S:Er3+,Yb3+ nanophosphors prepared by combustion synthesis.Figure optionsDownload as PowerPoint slide