A multi-color persistent luminescent phosphor Ca3Al2Ge3O12:Re3+ (Re3+=Tb3+, Pr3+, Dy3+) for dynamic anti-counterfeiting

Anticounterfeiting is a highly required technique to protect the product and consumer rights in modern society. The traditional anti-counterfeiting luminescent materials are generally presented as monochromatic emission and fixed excitation modes. Here, rare earth ions (Re 3+ =Tb 3+ , Pr 3+ , Dy 3+ ) doped Ca 3 Al 2 Ge 3 O 12 can produce the novel multi-modal and multi-color long afterglow anti-counterfeit material. When adjusted the Tb 3+ concentration, the different trap types, the trap concentrations and trap depths were formed, leading to the different afterglow of Ca 3 Al 2 Ge 3 O 12 :Tb 3+ duration from 4 to 24 h. The long afterglow color of Ca 3 Al 2 Ge 3 O 12 :Pr 3+ can turn from red to green by the cross-relaxation process with changing the Pr 3+ ions concentration. The afterglow color of Ca 3 Al 2 Ge 3 O 12 :Dy 3+ can change from blue to cyan due to the different afterglow decay lifetimes of the Dy 3+ emission peaks. Based on the above luminous mode Ca 3 Al 2 Ge 3 O 12 :Re 3+ (Re 3+ =Tb 3+ , Pr 3+ , Dy 3+ ), developed multiple anti-counterfeiting devices that can be used for passport and fingerprint verification, etc. In addition, under the high-temperature conditions, there will still be an afterglow color display, and the multi-level anti-counterfeiting strategies can be used to solve counterfeiting problems in various fields. • Three different afterglow anti-counterfeiting modes were prepared. • The afterglow time of 4%–5%Tb 3+ is about 4–24 h. • 7% Pr 3+ shows green, 2% Pr 3+ shows orange-red. • The 1%Dy 3+ afterglow color changes from blue to cyan over time.