Trap depth engineering in MgGa2O4: Bi3+ for muticolor dynamic anti-counterfeiting, encryption and optical temperature sensing applications

Anti-counterfeiting and encryption are key technologies for information transmission in modern society. Whereas, most optical materials reported only provide single luminous color and fixed response mode, which limits their safety in advanced anti-counterfeiting applications. In this work, we reported a Bi 3+ -assisted trap depth engineering strategy to achieve a dual-mode dynamic photoluminescence response of MgGa 2 O 4 : Bi 3+ with intriguing anti-counterfeiting and encryption performances. Upon the ultraviolet (UV) of 254 nm irradiation for 20 s, the color of MgGa 2 O 4 : x% Bi 3+ (x = 0, 1.0, 2.0, 3.0, 5.0) samples showed dynamic transformation from green or near-infrared to bluish-white emission. Combined with the dynamic photoluminescent (PL) behavior of MgGa 2 O 4 : 2.0% Bi 3+ , high-level dynamic anti-counterfeiting and encryption properties of MgGa 2 O 4 : Bi 3+ for tagging spies were investigated through powder filling followed by a masked screen printing method. On the other hand, the fluorescence intensity ratios (FIR) of I 430 nm /I 500 nm and I 430 nm /I 709 nm for MgGa 2 O 4 : 2.0% Bi 3+ showed excellent temperature-dependent quenching behaviors in the temperature range of 283 to 393 K, and the relative temperature sensitivities for FIR of I 430 nm /I 500 nm and I 430 nm /I 709 nm are 2.18% and 2.98% K −1 at 283 K, respectively. These results inspired more flexible designs to safeguard information security and develop novel high-efficiency optical temperature detectors.