Light‐Responsive Carbon Dots with Photochromism and Excitation‐Dependent Room Temperature Phosphorescence

ABSTRACT Light‐responsive materials are of great interest for the development of next‐generation multifunctional optoelectronic devices. However, the rational design of carbon dots (CDs) with well‐defined multichannel emissive behavior remains challenging due to their complex structures and elusive luminescence mechanisms. In this work, photochromic CDs simultaneously exhibiting excitation‐dependent room temperature phosphorescence (ED‐RTP) were successfully prepared via a one‐step microwave‐assisted synthesis using 1,4,5,8‐naphthalenetetracarboxylic acid and poly‐ L ‐lysine as precursors. The resulting N‐CDs display pronounced and reversible photochromic behavior under 365 nm UV irradiation, along with long‐lived green and orange–red afterglow emissions upon switching off excitation at 295 and 365 nm, respectively. These unique dual‐mode luminescence features are mainly attributed to the in situ generation of naphthalimide radical species, along with emissive centers associated with both the carbon core state and the surface state. Benefiting from this dual‐mode luminescence behavior, which integrates photochromism and ED‐RTP, the N‐CDs show great potential for high‐level security applications, including multi‐state anti‐counterfeiting and multidimensional information encryption. Overall, this work offers a feasible strategy for constructing multifunctional phosphorescent CD‐based materials and broadens the scope of intelligent light‐responsive systems for advanced security identification and artificial‐intelligence‐related applications.