Surface‐Functionalized Carbon Dots with Photochromic Luminescence in Water and PVA Film

Abstract As a kind of light‐responsive material, carbon dots (CDs) have important application values in the fields of anti‐counterfeiting, information encryption, and biological imaging. However, currently, there are few reports on the photochromic luminescence phenomenon of CDs, and there is a lack of in‐depth research on the structural design and luminescence mechanism of CDs with photochromic luminescence. In this study, CDs with the structure of naphthalimide derivatives are synthesized by a one‐step method through a reasonable selection of precursors. Under continuous ultraviolet light irradiation, CDs achieved photochromic luminescence from 425 to 640 nm within 0 to 30 s, and this property is enhanced after being compounded with a polyvinyl alcohol film. Research analysis shows that the structure of the naphthalimide derivative on the surface state of the CDs undergoes structural changes during the ultraviolet light irradiation process, activating the surface state luminescence center. The surface state luminescence center and the core state luminescence center constitute the dual emission centers of CDs. Based on the excellent full‐color photochromic properties of CDs in polyvinyl alcohol, we have designed applications in portable UV detection and advanced dynamic information encryption, demonstrating promising application prospects. This study provides new insights into the photochromic luminescence of CDs.