Co-doping Mn2+/Cr3+in ZnGa2O4 to fabricate chameleon-like phosphors for multi-mode dynamic anti-counterfeiting

Nowadays, fluorescent printing technology for anti-counterfeiting is widely used because of its high-throughput, simplicity of design, and facile identify. However, it is very difficult to develop the fluorescent materials for anti-counterfeiting with capability of easy to identify and difficult to imitate. Here, multi-mode fluorescent materials of ZnGa2O4:Cr3+, Mn2+ for anti-counterfeiting were synthesized by a traditional solid state reaction. In this spinel solid solution, Mn2+ and Cr3+ ions occupy the tetrahedral site (Zn site) and octahedral site (Ga site) respectively, which emit green and near infrared (NIR) light peaking at similar to 503 nm and similar to 708 nm, along with green and NIR afterglows. The prepared materials have a potential of multimode dynamic luminescence, because they are highly sensitive to the composition, the excitation wavelength, and the detecting time. Therefore, they output tunable multi-color radiations, exchangeable visible and NIR signals, changeable afterglows through varying the test conditions. The chameleon-like phosphors were finally applied in anti-fake patterns and Quick Response Code through 3D printing and screen printing techniques. The results indicate that the phosphors are potential fluorescent materials for information encryption and anti-counterfeiting.