A Temporal and Space Anti-counterfeiting Based on the Four-Modal Luminescent Ba₂Zr₂Si₃O₁₂ Phosphors

Fluorescent anti-counterfeiting materials have been widely studied due to their high resolution and convenient identification by direct visualization of the color output. To date, the anti-counterfeiting technology of single ultraviolet excitation mode still has security problems because the single mode could be imitated easily. Here, we have successfully developed four modes of anti-counterfeiting from Eu²⁺ and Er³⁺ co-doped Ba₂Zr₂Si₃O₁₂ phosphors with photo, long persistent, photo-stimulated, and up-conversion luminescence behavior. The as-fabricated phosphors can emit an intense blue-green luminescence originating from the characteristic transition of Eu²⁺ ions and exhibit a blue-green long persistent luminescence phenomenon. Moreover, the enhancement of photo-stimulated luminescence that contributed to the effectively increased trap concentration is observed, along with the produced up-conversion phenomenon thanks to the introduction of Er³⁺ ions. Notably, the fluorescence rapidly changes from blue-green to stable green luminescence with the delay of excitation time under the excitation of a 980 nm laser diode. Herein, this work realizes the fast down- to up-conversion luminescence output over time, which provides the basis for its possible application in advanced multi-mode anti-counterfeiting.