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.