Structure and upconversion luminescence properties of BaYF5:Yb3+, Er3+ nanoparticles prepared by different methods

BaYF5:Yb3+, Er3+ (BYF) upconversion (UC) luminescence nanoparticles have been prepared using co-precipitation and hydrothermal techniques, respectively. Two different fluoride sources were used to synthesize BYF by the hydrothermal method, and the sizes of the as-prepared spherical particles were about 30 nm (NH4BF4 as a fluoride source) and 100 nm (NH4HF2 as a fluoride source), respectively. While the nanoparticles prepared by the co-precipitation method are irregular, many clusters and agglomerates can be seen. The UC fluorescence has been realized in all the as-prepared BYF samples upon 980 nm excitation. It is found that their luminescence spectra depend strongly upon the preparation method. Factors affecting the upconversion fluorescent intensity have been also studied. The UC emission transitions for 4F9/2–4I15/2 (red), 2H11/2–4I15/2 (green) and 4S3/2–4I15/2 (green) in the Yb3+/Er3+ codoped BYF nanoparticles depending on pumping power have also been discussed.