Multiple stimuli dual-optical mode responsive hybrid copper(i) halides for advanced anti-counterfeiting and information encryption

Abstract

Hybrid Cu(I)-based halides possess significant potential in optical anti-counterfeiting due to their diverse crystal structures and unique optical properties. Nevertheless, the synthesis of multi-optical mode responsive hybrid Cu-based halides remains a formidable challenge for achieving high-security optical encryption. Herein, two hybrid Cu-based halides featuring distinct [Cu₂I₄]²⁻ and [Cu₄I₆]²⁻ inorganic units, namely (MePPh₃)₂Cu₂I₄·DMF and (MePPh₃)₂Cu₄I₆ (MePPh₃⁺ = C₁₉H₁₈P⁺), are obtained through solvent volatilization. The colorless (MePPh₃)₂Cu₂I₄·DMF crystals exhibit cyan emission upon UV light irradiation, whereas the yellow (MePPh₃)₂Cu₄I₆ crystals emit vivid yellow photoluminescence under either UV or blue light. Furthermore, the structural transformation from (MePPh₃)₂Cu₂I₄·DMF to (MePPh₃)₂Cu₄I₆ can be triggered by ethanol, inducing changes in both the visual crystal color and luminescence color, thus showcasing a dual-optical mode response. Benefiting from these unusual properties, optical anti-counterfeiting and information encryption systems are constructed based on these hybrid metal halides. This work not only enriches the stimulus-responsive hybrid halide family, but also provides a novel platform for multifaceted applications in advanced anti-counterfeiting and information encryption.