Self-reduction induced CaAl₁₂O₁₉:Eu^2+/3+: A phosphor with dynamic photoluminescence and photochromism for advanced anti-counterfeiting and encryption

Dynamic photoluminescence and photochromism are two critical technologies applied in advanced anti-counterfeiting and encryption. In this work, an innovative phosphor of CaAl₁₂O₁₉:Eu^2+/3+ combining the features of dynamic photoluminescence and photochromism is developed for the first time. After being irradiated by a portable 254 nm ultraviolet lamp, the photoluminescent color of the phosphor can dynamically change from red to magenta in dark field, and the surface color can dynamically alter from white to light brown in bright field. Based on these two appealing features, an application in advanced anti-counterfeiting and encryption is designed which can write, encrypt, and erase information successfully, thus guaranteeing information security. Furthermore, a composite material of CaAl₁₂O₁₉:Eu^2+/3+/PDMS is fabricated for application in advanced anti-counterfeiting and encryption in both dark and bright fields, which is difficult to be replicated.