Electrostatic-Driven Coordination Interaction Enables High Specificity of UO22+ Peroxidase Mimic for Visual Colorimetric Detection of UO22+

Artificial enzyme mimics are more stable and cost-effective than bioenzymes, but they usually lack substrate recognition function. Here, we report that uranyl (UO22+) features efficient artificial peroxidase activity with a high specificity and can catalyze the oxidation of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium (ABTS) by H2O2 to yield green ABTS radical (ABTS•+), whereas other common substrates such as 3,3′-diaminobenzidine (DAB), 3,3′,5,5′-tetramethylbenzidine (TMB), o-phenylenediamine (OPD), and dopamine (DA) are not oxidized. The high specificity of UO22+ peroxidase mimic is ascribed to the electrostatic-driven coordination interaction between ABTS anion and UO22+ cation, and the orthorhombic metastudtite from the reaction between H2O2 and UO22+ rather than reactive radicals is identified as the key intermediate, which accounts for ABTS oxidation. On the basis of the UO22+ peroxidase mimic, a facile, low-cost, and reliable colorimetric assay is fabricated. The resulting colorimetric assay displays a good analytical performance for UO22+ detection in a linear range of 10–100 μM, along with a limit of detection of 0.5 μM. Further, the present colorimetric assay has a good selectivity toward UO22+ over common metal ions, which is applied for determination of UO22+ in natural water samples with satisfactory recovery results.