A Long-Term Stable Sensor Based on Fe@PCN-224 for Rapid and Quantitative Detection of H₂O₂ in Fishery Products

Hydrogen peroxide (H₂O₂) has been reported to be used for the illegal treatment of fishery products in order to obtain "fake" freshness. Residues of H₂O₂ 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 H₂O₂ concentration. The hybrid structure of Fe@PCN-224 was fabricated by incorporated free Fe^III ions into the center of PCN-224, which was ultra-stable due to the strong interactions between Zr₆ 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 H₂O₂ 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 H₂O₂.