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 ~ 503 nm and ~ 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.