Carbon-based nanozymes: catalytic mechanisms, performance tuning, and environmental and biomedical applications

Carbon-based nanozymes-a significant subclass of nanomaterials mimicking natural enzyme catalytic functions-offer superior thermal/chemical stability and enhanced biocompatibility compared to natural enzymes and other nanozyme types, owing to their unique carbon matrix. This review comprehensively examines research progress in carbon-based nanozymes. It details their classification into three categories: (1) carbon nanozymes (e.g., fullerenes, graphene, carbon dots, and nanotubes), (2) heteroatom-doped variants (N, P, S, and Se), and (3) metal/metal oxide-supported types, including single-atom nanozymes with M-N_x-C sites. The primary catalytic mechanisms, focusing on peroxidase (POD)-like and superoxide dismutase (SOD)-like activities, alongside oxidase (OXD)-like and catalase (CAT)-like mechanisms, are discussed. Strategies for regulating nanozyme performance-such as size/morphology control, composition/structure tuning (doping and defect engineering), surface modification, biomolecular interactions, and external environment manipulation (pH and temperature)-are highlighted. The review emphasizes the broad applications of carbon-based nanozymes in environmental engineering (pollutant detection/degradation), biosensing (H₂O₂, biomolecules, antioxidants, and tumor markers), and biomedicine (antioxidant/anti-inflammatory therapy, tumor treatment, antibacterial/antiviral applications, and bioimaging). Finally, it addresses existing challenges, including relatively lower activity/specificity compared to natural enzymes, limited enzyme-mimicking types, unclear atomic-scale mechanisms, synthesis control difficulties, biocompatibility/safety concerns, and the need for standardized research frameworks. This overview underscores the immense potential and future research directions for carbon-based nanozymes.