Photochromism and dynamic photoluminescence in CaAl12O19:Eu, Ce phosphor for dual-mode anti-counterfeiting and encryption applications

Dual-mode anti-counterfeiting materials with photochromic and dynamic luminescent properties can improve the security of anti-counterfeiting and encryption. This study aimed to synthesize CaAl 12 O 19 :Eu, Ce phosphors with photochromic and dynamic photoluminescent properties. With the extension of 254-nm UV radiation time, the surface of the CaAl 12 O 19 :Eu, Ce phosphors changed in color from white to brownish yellow and was bleached by heating at 520 °C for 5 min, exhibiting excellent fatigue resistance and thermal stability. After co-doping Eu and Ce in CaAl 12 O 19 , the photochromic performance significantly improved, with the ΔR value increasing by 2.6- and 1.8-fold that of the CaAl 12 O 19 :1.0%Eu and CaAl 12 O 19 :1.0%Ce sample‌s, respectively. After 254-nm UV irradiation, the CaAl 12 O 19 :Eu, Ce samples showed time-dependent dynamic luminescence characteristics, changing in color from orange-red to magenta. The mechanisms responsible for the photochromic and dynamic luminescence properties were further investigated. Overall, owing to their photochromism and dynamic photoluminescence, the CaAl 12 O 19 :Eu, Ce/polydimethylsiloxane composites could be applied in advanced anti-counterfeiting and information encryption with higher security in both the bright and dark fields.