LAUSR

Anticounterfeiting is a vitally important issue in modern society. At present, the most commonly used luminescent anticounterfeiting technique is based on static photoluminescence (PL), which is easily counterfeited by certain substitutes. In this work, we report for the first time a dynamic PL material, Na2CaGe2O6:Tb3+. Irradiated by a portable ultraviolet (254 nm) lamp, the PL color of the material due to Tb3+ changes from the initial red to yellow and, finally, to green. The investigation reveals that the dynamic PL is due to the presence of appropriate traps and a cross-relaxation effect of Tb3+ in Na2CaGe2O6. By employing this unique dynamic PL material, high-level dynamic luminescent anticounterfeiting and encryption devices are fabricated. The dynamic PL features of the devices are easily detected using a cheap portable lamp, and at present it is impossible for the features to be faked by any substitutes. In a virtual military scenario, the results demonstrate that the encryption device is safe and the spy will be detected. Accordingly, this dynamic PL material could inspire us with more ingenious security designs.