| Summary: | Hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) has been reported to be used for the illegal treatment of fishery products in order to obtain “fake” freshness. Residues of H<sub>2</sub>O<sub>2</sub> in food may be of toxicology concern. In this study, a nonenzymatic sensor was developed based on Fe@PCN-224 metal–organic frameworks wrapped by Nafion to detect H<sub>2</sub>O<sub>2</sub> concentration. The hybrid structure of Fe@PCN-224 was fabricated by incorporated free Fe<sup>III</sup> ions into the center of PCN-224, which was ultra-stable due to the strong interactions between Zr<sub>6</sub> and the carboxyl group. Scanning electron spectroscopy images exhibited that Nafion sheets crossed together on the surface of Fe@PCN-224 nanoparticles to form a hierarchical and coherent structure for efficient electron transfer. Electrochemical investigations showed that the Fe@PCN-224/Nafion/GCE possessed good linearity from 2 to 13,000 μM (including four orders of magnitude), low detection limits (0.7 μM), high stability in continuous monitoring (current remained nearly stable over 2300 s) and in long-term measurement (current decreased 3.4% for 30 days). The prepared nanohybrid modified electrode was effectively applied to H<sub>2</sub>O<sub>2</sub> detection in three different fishery products. The results were comparable to those measured using photometrical methods. The developed electrochemical method has a great potential in detecting the illegal management of fishery products with H<sub>2</sub>O<sub>2</sub>.
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