Smartphone-assisted colorimetric sensor array based on trimetallic FeMnZn-NC nanozyme for the pattern recognition of antioxidants in fruit

Antioxidants such as ascorbic acid, glutathione, gallic acid, and caffeic acid are crucial for food quality and human health, yet their simultaneous discrimination in complex food matrices remains challenging due to overlapping reactivities. In this study, we developed a robust colorimetric sensor array based on trimetallic FeMnZn‑nitrogen‑carbon (FeMnZn-NC) nanozymes. Synthesized via high-temperature pyrolysis, the introduction of Zn as a sacrificial template generates abundant structural defects and exposes more active sites, resulting in significantly enhanced oxidase-like activity compared to mono- and bimetallic analogues. The nanozymes catalyze the rapid oxidation of TMB and ABTS substrates within 2 min, a process differentially inhibited by distinct antioxidants via varying electron-transfer and chelating mechanisms. Leveraging these unique kinetic “fingerprints,” a dual-channel sensor array was constructed to identify ascorbic acid, glutathione, gallic acid, and caffeic acid, exhibiting linear responses over 0–40 μM with detection limits of 0.22, 0.43, 0.21, and 0.14 μM, respectively. The sensor demonstrated excellent anti-interference capability and was effectively applied to identify antioxidants in apples, pears, and kiwifruits. The integration of a smartphone-assisted colorimetric platform enables rapid, on-site detection, highlighting its strong potential for food quality monitoring and nutritional assessment.