Multimode Dynamic Photoluminescence of Bi3+-Activated ZnGa2O4 for Optical Information Encryption

Optical storage technology for information encryption is a popular means of safeguarding information. Herein, a Bi³⁺-activated ZnGa₂O₄ multimode dynamic photoluminescence (PL) material is developed. Upon being irradiated with an ultraviolet lamp at a fixed excitation wavelength of 254 nm, the ZnGa₂O₄: x% Bi³⁺ (x = 0.5-5.0) samples exhibit varying degrees of dynamic PL emission due to a distinct Bi³⁺ doping effect. The mechanism underlying the dynamic PL of ZnGa₂O₄: Bi³⁺ associated with Bi³⁺-activated trap concentration modulation is investigated using thermoluminescence spectra. Additionally, the ZnGa₂O₄: 5% Bi³⁺ sample shows a reversible thermally responsive dynamic PL with a color variation from blue to red upon heating from 283 to 393 K. Predesigned procedures based on single-wavelength-mediated photochromic and thermochromic dynamic PL emissions of ZnGa₂O₄: Bi³⁺ are designed for rewritable optical data storage and high-level information encryption. Also, an enhanced encryption scheme with a mask encoding technique applying a ZnGa₂O₄: Bi³⁺ hybridized polyvinylidene difluoride film is then proposed to increase the security level. Accordingly, this work provides a feasible way to rationally design dynamic PL material offering more creative designs for safeguarding information via encryption.