Synthesis of Co/Ce Dual Active Sites Single-Atom Cerium Nanozyme with the Synergistic Effect and Peroxidase-like Activity for Total Antioxidant Capacity Evaluation.

The design and modulation of the catalytic activity of nanozymes are critical for advancing their development. In this study, a novel Ce-based single-atom nanozyme with Co/Ce dual-metal active sites (named Co-Ce@NC) was successfully synthesized. Co-Ce@NC exhibits excellent peroxidase-like (POD) activity, demonstrating both enhanced affinity and an accelerated reaction rate for H2O2. This may be attributed to the high single-atom loading (Ce: 9.61 wt %; Co: 0.46 wt %) caused by surface defects of the material and the synergistic effect between Co and Ce, which enhance the Ce3+/Ce4+ ratio and thereby rapidly trigger the production of reactive oxygen species (ROS) from H2O2. Based on the competition between ascorbic acid (AA) and ROS during the oxidation of TMB, a colorimetric platform was developed to detect the total antioxidant capacity (TAC). This platform was applied for detecting TAC in commercial beverages and fruits, indicating its significant potential for evaluating antioxidant quality in food. This study not only introduces a novel approach for enhancing the performance of Ce-based single-atom nanozymes but also emphasizes their broad applicability in TAC detection.