Highly efficient carbon supported Co–Ir nanozyme for the determination of total antioxidant capacity in foods

Nanozyme-based colorimetric assays have aroused extensive attention in biosensing due to quick response, low cost and simplicity. However, their practical applications are limited by the unsatisfactory stability and catalytic activity of nanozymes in complex detection environments. Herein, using the one-pot chemical vapor deposition method, we successfully prepare a highly efficient and stable carbon supported Co-Ir nanozyme (termed as Co-Ir/C nanozyme) for the determination of total antioxidant capacity (TAC) in food samples. The Co-Ir/C nanozyme shows excellent durability under extensive pH ranges, high temperature and high salt concentration due to the protection of carbon supporter. It can be recycled by simple magnetic separation, and its catalytic activity remains stable after long-term operation and storage. Taking full advantage of the superior peroxidase-like activity of Co-Ir/C nanozyme, it is used for colorimetric detection of ascorbic acid (or known as vitamin C), an important vitamin to adjust body's normal physiological function, with results showing higher sensitivity (detection limit of 0.27 μM) than most of the recently published works. Moreover, the determination of TAC in vitamin C tablets and fruits are further achieved, which are in good agreement with those of commercial colorimetric test kits. This study helps guide the rational preparation of versatile and highly stable nanozymes, and develops a robust TAC determination platform for future food quality monitoring.