Photo/pH dual-tunable circularly polarized luminescence in liquid crystals enabled by a chiral fluorescent photoswitch for advanced information encryption

The regulation of circularly polarized light (CPL) plays a crucial role in asymmetric catalysis and photonic functional devices. Photonic functional devices utilizing multi-responsive integrated chiral fluorescent photoswitches (CFPSs) as core components exhibit enhanced CPL signal modulation capabilities. By strategically combining liquid crystals (LC) with novel CFPSs, we develop smart materials capable of diverse CPL modulation behaviors including photo-induced CPL “turn on” and pH-induced CPL “turn off”. For achieving this aiming, the newly synthesized CFPS named Switch-ADAE not only inherits the inherent photoresponsiveness of diarylethene (DAE) frameworks but also demonstrates pH-responsiveness through pyridine group incorporation. Furthermore, the cholesteric liquid crystal (CLC) system composed of Switch-ADAE and nematic LCs exhibits synergistic light/pH multi-responsiveness. Under UV/visible light illumination, this system enables reversible fluorescence and CPL signal on/off switching. The introduction of TFA/TEA into the closed-ring isomer further facilitates reversible redshifts in fluorescence wavelengths and CPL signal deactivation, thereby establishing a dual-regulation CPL modulation system. Finally, a multi-mode information encryption system leveraging pH-responsive modulation and CPL compensation in CLC systems doped with Switch-ADAE. This proof-of-concept demonstrates the potential of such hybrid materials in developing advanced secure communication technologies and high-density information storage solutions.