Ethanol-assistant solution combustion method to prepare La2O2S:Yb,Pr nanometer phosphor

La2O2S:Yb,Pr nanometer phosphor have been prepared by a novel ethanol-assistant solution combustion (EASC) method in ethanol–water solution medium via a relatively mild and slow combustion process, using ethanol as preigniting fuel and inexpensive thioacetamide as sulfur-containing organic fuel. Investigation results show: ethanol preigniting serves the role of ignition combustion decomposition reaction between rare earth nitrate and organic fuel and promotes the formation of uniform and less agglomerative rare earth oxysulfide nanocrystals. Single phase Ln2O2S:Yb,Pr nanocrystals are obtained with appropriate ethanol/water ratio and further annealing at 1000 °C for 2 h in reduced atmosphere. The La2O2S:Yb,Pr nanocrystals exhibit an intense green emission assigned to the Pr3+ ions 3P0 → 3H4 transition and a broad near infrared (NIR) emission under 980 nm pump. The defects residing in La2O2S:Yb,Pr nanocrystals is the probable origins for the NIR emission. The annealing process makes the green emission improve and the NIR emission weaken. After annealing treatment at 1000 °C, the upconversion luminescence intensity is close to that of the bulk sample prepared by a solid-state reaction method.