Combustion synthesis and up-conversion luminescence of La{sub 2}O{sub 2}S:Er{sup 3+},Yb{sup 3+} nanophosphors
La{sub 2}O{sub 2}S:Er{sup 3+},Yb{sup 3+} 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 La{sub 2}O{sub 2}S:Er{sup 3+},Yb{sup 3+} nanoparticles, of the order of 50–200 nm, are obtained after a post-treatment in a H{sub 2}S/N{sub 2} flow for 2 h at 1000 °C. The efficient energy transfer from Yb{sup 3+} to Er{sup 3+} results in a strong up-conversion upon excitation at 980 nm. The emission spectra show the intense green emissions corresponding to the ({sup 2}H{sub 11/2}, {sup 4}S{sub 3/2})→{sup 4}I{sub 15/2} transitions and a red emission corresponding to the {sup 4}F{sub 9/2}→{sup 4}I{sub 15/2} transition. Additionally, within the investigated co-doping concentrations, no significant concentration quenching effect and back energy transfer from Er{sup 3+} to Yb{sup 3+} were evidenced. This research highlights the influence of the sulfurization treatment on the purity/crystallinity/morphology of the nanocrystals and the luminescence efficiency. - Graphical abstract: Up-conversion luminescence of La{sub 2}O{sub 2}S:Er{sup 3+},Yb{sup 3+} nanophosphors prepared by combustion synthesis. - Highlights: • La{sub 2}O{sub 2}Er{sup 3+}, Yb{sup 3+} 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{sup +} to Er{sup 3+} 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 H{sub 2}S/N{sub 2} flow on UPL efficiency.