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

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 [Cu 2 I 4 ] 2− and [Cu 4 I 6 ] 2− inorganic units, namely (MePPh 3 ) 2 Cu 2 I 4 ·DMF and (MePPh 3 ) 2 Cu 4 I 6 (MePPh 3 + = C 19 H 18 P + ), are obtained through solvent volatilization. The colorless (MePPh 3 ) 2 Cu 2 I 4 ·DMF crystals exhibit cyan emission upon UV light irradiation, whereas the yellow (MePPh 3 ) 2 Cu 4 I 6 crystals emit vivid yellow photoluminescence under either UV or blue light. Furthermore, the structural transformation from (MePPh 3 ) 2 Cu 2 I 4 ·DMF to (MePPh 3 ) 2 Cu 4 I 6 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.