Spy Must Be Spotted: A Multistimuli-Responsive Luminescent Material for Dynamic Multimodal Anticounterfeiting and Encryption.

The development of luminescent materials for anticounterfeiting and encryption is of great importance. Herein, we develop a multistimuli-responsive luminescent material, Na2CaGe2O6:Pb2+/Er3+, and use it to print luminescent images. The photoluminescence and upconversion luminescence of these images show different patterns and colors under different stimuli. The photostimulated luminescence (PSL) of the printed images causes dynamic changes in appearance and is accordingly applied for dynamic multimodal anticounterfeiting on banknotes. The PSL of these luminescent images is also applied in a virtual war scenario to demonstrate that the dynamic PSL-encrypted information in the fabricated image is sufficiently safe even in extreme cases and that spies will be detected. These results can inspire us with more creative security designs based on this luminescent material.