Matrix‐Free Afterglow Carbon Dots: Synthetic Strategies, Luminescence Mechanisms, and Emerging Applications

Afterglow materials, due to their long luminescence lifetime and excellent optical properties, have significant application value in information encryption, optical anti‐counterfeiting, bioimaging, and optoelectronic devices. Traditional afterglow materials, such as inorganic rare earth compounds and organometallic complexes, suffer from high cost and toxicity, whereas pure organic materials are limited in development due to weak spin–orbit coupling and low intersystem crossing efficiency. Carbon dots (CDs), as low‐toxicity, low‐cost, and biocompatible nanomaterials, provide a new platform for the design of afterglow materials. Among them, matrix‐free afterglow CDs can achieve efficient and long‐lifetime luminescence without relying on an external matrix, including both afterglow and delayed fluorescence types, exhibiting advantages such as stimulus responsiveness and good solution processability, showing broad prospects in intelligent sensing, information encryption, flexible optoelectronic devices, and bioimaging. This review systematically elucidates the luminescence mechanism, synthesis methods of matrix‐free afterglow carbon dots, and their application progress in information encryption, light‐emitting diodes, sensing, bioimaging, and tumor treatment, and finally, discusses the current challenges and future development directions.