Bioinspired FeN₅ Sites with Enhanced Peroxidase-like Activity Enable Colorimetric Sensing of Uranyl Ions in Seawater

Nanozymes with peroxidase (POD)-like activity have garnered significant attention due to their exceptional performance in colorimetric assays. However, nanozymes often possess oxidase (OD) and POD-like activity simultaneously, which affects the accuracy and sensitivity of the detection results. To address this issue, inspired by the catalytic pocket of natural POD, a single-atom nanozyme with FeN₅ configuration is designed, exhibiting enhanced POD-like activity in comparison with a single-atom nanozyme with FeN₄ configuration. The axial N atom in FeN₅ highly mimics the amino acid residues in natural POD to optimize the electronic structure of the metal active center Fe, realizing the efficient activation of H₂O₂. In addition, in the presence of both H₂O₂ and O₂, FeN₅ enhances the activation of H₂O₂, effectively avoiding the interference of dissolved oxygen in colorimetric sensing. As a proof-of-concept application, a colorimetric detection platform for uranyl ions (UO₂²⁺) in seawater is successfully constructed, demonstrating satisfactory sensitivity and specificity.