Solution‐Phase Carbon Dot‐Based Room‐Temperature Afterglow Materials: Design Strategies and Applications

Room‐temperature afterglow (RTA) materials are promising for bioimaging, chemical sensing, information encryption, and optoelectronic devices because they emit after excitation ceases. Carbon dots (CDs) provide an eco‐friendly and versatile platform for solution‐phase RTA, but molecular motion and dissolved oxygen in liquids promote non‐radiative relaxation and triplet‐exciton quenching. This review critically examines the design and performance of CD‐based RTA materials in aqueous and non‐aqueous media. Solution‐phase afterglow is governed by the interplay among emissive centers, protective matrices, interfacial interactions, and solvent environments. Current strategies are organized into rigid confinement, excited‐state modulation and energy transfer, water‐enhanced regulation, interfacial adaptation, solvent‐mediated regulation, and machine‐learning‐guided design. The distinct requirements of aqueous and non‐aqueous systems are compared, together with recent applications in bioimaging, sensing, information security, and optoelectronic devices. Finally, key challenges in efficiency, stability, mechanistic understanding, and cross‐medium applicability are discussed to guide the development of practical solution‐phase CD‐based RTA materials.