Fe, N-doped carbon dots/RF in self-Fenton cascade reaction: Improved photodegradation mechanism and toxicity evaluation

The nanozyme, identified among the top ten emerging technologies in chemistry, has shown rapid development in nano-catalysis for tumour treatment, particularly through its Fenton-like reaction. Herein, a novel iron, nitrogen-doped carbon dots (Fe, N-CDs) with nanozyme catalytic properties was designed, which was then surface-modified onto resorcinol-formaldehyde (RF) resin. Subsequently, a heterogeneous photo-Fenton-like cascade system was constructed to produce and activate photo-generated hydrogen peroxide (H₂O₂) in situ. Within a broad pH range of 5–9, Fe, N-CDs/RF composites demonstrated superior photocatalytic activity compared to RF alone. Under visible light irradiation, degradation of chloroquine phosphate (CQ) was achieved with a degradation rate constant (k) 3.2 times higher than that observed for RF. Active species capture experiments revealed that hydroxyl radicals (•OH) and superoxide radicals (•O₂^-) are crucial in propelling the photocatalytic reaction. Furthermore, Density Functional Theory (DFT) calculations indicated that introduction of nanozymes enhances the transfer of electrons from RF surfaces to Fe, N-CDs, high adsorption ability of Fe, N-CDs towards H₂O₂ (E_ads=-5.45 eV) in the Fe, N-CDs/RF composites was exploited, thereby augmenting their photocatalytic activity. The possible degradation mechanism of CQ was proposed, and environmental toxicity of CQ degradation intermediates was assessed by seed experiments. This study extends the application scope of carbon dot nanozymes in self-sufficient photo-Fenton systems.