Palladium/Rhodium/Iridium Trimetallic Octahedral Nanozymes Exhibiting Enhanced Peroxidase-like Activity for Detecting Total Antioxidant Capacity in Food

Nanozymes are widely used in detecting biomarkers. However, designing nanozymes exhibiting high peroxidase-like activity is challenging. This study aimed to synthesize two types of nanozymes, Pd–Rh–Ir nanozyme (PRI nanozyme) and Pd–Ir nanozyme (PI nanozyme), exhibiting similar morphologies and enhanced activities. The first nanozyme comprised palladium, rhodium, and iridium (PRI nanozyme), while the second nanozyme comprised palladium and iridium (PI nanozyme). The PRI nanozyme exhibited a higher peroxidase-like activity than the PI nanozyme. Rhodium in the subsurface of the PRI nanozyme can lower the hydrogen peroxide decomposition energy and increase the hydroxyl radical (•OH) content in a catalytic system. As a proof of concept, the PRI nanozyme was used to detect ascorbic acid, cysteine, and glutathione, with limits of detection (LODs) being 0.14, 0.18, and 0.21 μM, respectively. Finally, the PRI nanozyme-based method was applied to determine the total antioxidant capacities (TACs) of different beverages, fruits, and vegetables. Among the tested samples, Actinidia Chinensis Planch exhibited the highest TAC. This study broadens the application of multimetallic nanozymes in the field of food quality and safety.