Novel BaY1-xGdxF5: Yb3+/Er3+/Bi3+ solid solution nanocrystals with enhanced upconversion luminescence and magnetism properties

Abstract

Fluoride phosphors with enhanced upconversion luminescence performance and multi-functionalization are urgently explored for applications in modern bio-detection and medical imaging. Here, a series of BaY1-xGdxF5: Yb/Er/Bi (0 ≤ x ≤ 0.5) solid solution nanocrystals are designed and synthesized. The influence of Gd3+-doping concentration on microstructure, upconversion luminescence, and magnetic performances are deeply reported. XRD results demonstrate the formation of solid solution with cubic phase structure. With increasing Gd3+ concentration, the diffraction angle gradually shifts toward lower direction as a result of replacing Y3+ by Gd3+ with larger ionic radius. Microstructure results show that the size distribution is between 60 and 100 nm and reveal that Gd3+ facilitates the growth of crystal grains. Upon 980 nm excitation, the BaY1-xGdxF5: Yb/Er/Bi samples demonstrate two dominant green and red emissions of Er3+ at 546 nm and 658 nm, respectively. By substituting Y3+ with Gd3+, the characteristic green luminescence can efficiently lead to an obvious enhancement at x = 0.2. The detailed enhancement mechanism is presented. Besides, the obtained nanocrystals show excellent paramagnetism properties, and the magnetic magnitude is significantly enhanced with increasing Gd3+ concentration. These results indicate that the BaY1-xGdxF5: Yb/Er/Bi nanocrystals are promising three-mode probes with potential applications in medical imaging and disease diagnosis.