Bi3+/Eu3+ Co-Activated Multimode Anti-Counterfeiting Material with White Light Emission and Orange-Yellow Persistent Luminescence

Abstract

Traditional anti-counterfeiting luminescent phosphors are usually composed of single-mode photoluminescence materials, which greatly limits the security of encryption by its static fluorescent pattern. Herein, multi-mode luminescence properties are achieved including fluorescence and persistent luminescence (PersL) within single host by co-doping Bi3+ and Eu3+ in CaNaSb2O6F (CNSOF). A tunable emission is observed from blue (Bi3+, 3P1→1S0) to white and then to orange-yellow (Eu3+, 5D1→7F2 and 5D0→7F0, 1, 2, 3, 4) as the excitation schemes, environment temperatures and doping level are modulated. Impressively, the blue emission attributed to the Bi3+ rapidly disappears after stopping the excitation light irradiation, and only the intense orange-yellow PersL produced by Eu3+ can be observed. And a possible model for the energy transfer and PersL mechanism is proposed by the investigation crystal structure and photoluminescence/PersL. A schematic of security logo and digital information encryption is demonstrated using the prepared samples, which shows the dynamic evolution of the emission color and PersL brightness. The excellent property of multiple color outputs, different decay processes, and external field stimulation modes (including low energy light, thermal, and mechanical stimuli) present in CNSOF:Bi3+, Eu3+ provides a fast, low-cost, and effective method for advanced anti-counterfeiting and information encryption applications.