Curvature Engineering of Single-Atom Cobalt Nanozymes for Efficient Dual-Mode Antioxidant Determination and Discrimination

Single-atom cobalt nanozymes are promising alternatives to natural oxidases, yet their catalytic performance is often constrained by support-dependent electronic interactions and overly symmetric coordination environments, leading to inefficient oxygen adsorption and activation. Herein, using concave carbon frameworks anchoring cobalt single atoms (CoNC-meso) as a model, we demonstrate that curvature engineering of the support offers an effective approach to address these intrinsic limitations. Experimental results show that CoNC-meso exhibits an approximately 1.5-fold higher catalytic efficiency than its planar counterpart (CoNC), highlighting the pivotal role of surface curvature in modulating the intrinsic activity. Density functional theory calculations reveal that the concave architecture elongates the Co–N bond, redistributes local charge density, and upshifts the Co d-band center toward the Fermi level, thereby strengthening O2 adsorption and promoting singlet oxygen (1O2) generation. Leveraging this enhanced oxidase-like activity, CoNC-meso efficiently catalyzes 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation. The generated oxidized TMB (oxTMB) serves dually as a colorimetric reporter and a photothermal transducer, enabling a sensitive colorimetric–photothermal dual-mode sensing platform for the discrimination and detection of antioxidants. This study not only underscores the critical importance of support curvature in single-atom nanozyme design but also opens an avenue for engineering high-performance nanozymes through geometric microstructure control.