Emodin-derived red-emissive carbon dots: Light-driven ROS generation and antioxidant activities in non-illuminative regimes

Reactive oxygen species (ROS) play dual roles in physiological processes and disease pathogenesis, making their precise regulation crucial for therapeutic applications. Herein, we report the rational design of red-emissive carbon dots (CDs) with light-switchable pro-oxidant/antioxidant bifunctionality for precision nanomedicine. Synthesized from emodin and urea via a solvothermal method, these N-doped CDs exhibit: (1) red emission (>650 nm) with enhanced tissue penetration, (2) efficient type I/II ROS generation under light irradiation, (3) effective ROS scavenging in darkness , and superior water solubility and biocompatibility for in vivo applications. Density functional theory (DFT) calculations confirm that N-doping optimizes the spectral properties of Emo-CDs and promotes the generation of ROS. The unique graphene-like core with abundant surface functional groups enables reversible switching between oxidative and antioxidative states under dark conditions. This work establishes a new paradigm for developing intelligent theranostic agents capable of precise oxidative stress regulation, with promising applications in photodynamic and antioxidant therapy.