Dual-mode optical thermometry and multicolor anti-counterfeiting based on Bi3+/Er3+ co-activated BaGd2O4 phosphor

Here, Bi3+, Er3+ co-activated gadolinium phosphors with multimode emission properties are prepared, which can emits blue, green, and orange light under the excitation of ultraviolet, 980 and 1550 nm, respectively. Moreover, BaGd2O4:Bi3+, Er3+ can show multicolor luminescence under different excitation conditions, such as pump light source, ambient temperature, working current, and other factors. Based on the dynamic luminescence characteristics, the dynamic anti-counterfeiting experiments are designed based on the phosphor. At the same time, the material also shows multimode temperature sensing characteristics. Under the excitation of 980 nm laser, three strong up-conversion signals Er3+ ions are generated at 528 nm (H-2(11/2)), 555 nm (S-4(3/2)), and 668 nm (F-4(9/2)), which have different temperature dependences. Based on the fluorescence intensity ratio between thermal-coupled energy levels (H-2(11/2)/S-4(3/2)) and nonthermal-coupled energy levels (H-2(11/2)/F-4(9/2)) of Er3+ ions, respectively, the dual-mode temperature thermometer was constructed with high-temperature sensitivity. In addition, the fluorescence lifetime of Bi3+ ions also has a strong temperature dependence, which can be used as another temperature detection signal, greatly improving the stability of thermometers under harsh conditions. Therefore, the material has a bright prospect in the field of anti-counterfeiting and temperature sensing.