Pr³⁺–Gd³⁺ co-doped Ba₂SiO₄ for multilevel anti-counterfeiting encryption

Developing anti-counterfeiting technology with a higher level of security is vital to boycott the fake commodities. Here, we report the detailed optical property of Ba2SiO4:Pr3+, Gd3+, and their potential applications in fluorescent anti-counterfeit. It has been confirmed that Pr3+ ions could emit the ultraviolet-C (UVC) photons upon excitation of a 450 nm laser, which originates from a two-photon upconverted mechanism. Moreover, the ultraviolet-B (UVB) light also appears simultaneously when co-doping Gd3+ into the host, due to the energy transfer from Pr3+ to Gd3+. Depending on the multimode emissions of Pr3+-Gd3+-codoped phosphors, including the routine magenta emission of Pr3+, as well as the UVC photons of Pr3+ and the UVB light of Gd3+, we successfully achieve multi-level anti-counterfeiting applications.