Water-Molecule-Induced Reversible Fluorescence in a One-Dimensional Mn-Based Hybrid Halide for Anticounterfeiting and Digital Encryption–Decryption

Hybrid metal halides with reversible transformation of structure and luminescence properties have attracted significant attention in anticounterfeiting. However, their long transition time and slow response rate may hinder the rapid identification of confidential information. Here, a one-dimensional hybrid manganese-based halide, i.e., (C₅H₁₁N₃)MnCl₂Br₂·H₂O, is prepared and demonstrates the phenomenon of water-molecule-induced reversible photoluminescence transformation. Heating for <40 s induces a dynamic transfer of red-emissive (C₅H₁₁N₃)MnCl₂Br₂·H₂O to green-emissive (C₅H₁₁N₃)MnCl₂Br₂. In addition, the green emission can gradually revert to red emission during a cooling process in a moist environment, demonstrating excellent reversibility. It is found that the water molecule acts as an external stimulus to realize the reversible transition between red and green emission, which also exhibits remarkable stability during repeated cycles. Furthermore, with the assistance of heating and cooling, a complex digital encryption–decryption and an optical “AND” logical gate are achieved, facilitating the development of anticounterfeiting information security.