Reversible Photoresponsive Multicolor Fluorescent Carbon Dots for Repeatable Dynamic Information Encoding

Photoresponsive carbon dots (CDs) materials have broad application prospects in fields such as ultraviolet (UV) light detection, advanced anticounterfeiting, and information encryption. However, developing color-tunable, photoresponsive CDs that can respond quickly and reversibly remains a significant challenge. In this work, we successfully achieved photoresponsive multicolor fluorescence emission from CDs by surface-modifying them with different concentrations of tetraethylenepentamine (TEPA), forming naphthalimide structures that respond to UV light. Importantly, the response time reached as fast as 0.5 s, and color reversibility was achieved through simple shaking without the need for additional stimuli. Research has shown that the generation of photoresponsive multicolor fluorescence is due to the formation of naphthalimide structures on the surface of the CDs, which produce radicals under continuous UV exposure. The different TEPA concentrations lead to varying amounts of radicals, thereby affecting the energy bandgap and resulting in multicolor fluorescence changes. On the basis of the differences in response times for different colors, we further developed a repeatable dynamic information encoding system that enables dynamic information storage and encryption.