Visible-light-driven photoresponsive color-changing materials with dual light signal outputs and enhanced performance for advanced applications†

Light-responsive color-changing materials (LCCMs) have garnered significant attention due to their passive response to external stimuli and their pronounced visual color changes. However, the progression of these materials into high-end applications has been significantly impeded by limitations such as suboptimal performance, including incompatible color contrast and retention time, dependence on ultraviolet light as a stimulus, inadequate reusability for rapid erasure, and reliance on a single coloring mode. To overcome these challenges, we present a visible-light-driven LCCM capable of real-time dual optical signal output (color change or fluorescence emission) with high color contrast and resolution, extended retention time, exceptional reproducibility, and facile multicolor printing. These superior attributes are derived from the application of a photoinduced proton transfer (PPT) strategy, as demonstrated by the newly designed and synthesized photochromic molecular photoswitches (MC-1 to MC-4). Leveraging this strategy, the LCCM exhibits significant color change and fluorescence switching in a real-time and highly reversible manner under simple visible-light control. Consequently, we demonstrate the light-activated anti-counterfeiting function of fluorescence and self-erasing light-controlled patterns, highlighting their potential applications in advanced information encryption. This work provides valuable insights into the design of smart optical materials.