Selective and sensitive colorimetric sensing of iodine ions based on porous MoS2 particles with excellent haloperoxidase-like activity

Nanozymes continue to attract great interest due to their high enzyme activities, good biocompatibility, chemical stability and adjustable activity, which have been widely used in biosensing, disease therapy and antibacterial treatment. Herein we report porous MoS2 particles to have both excellent bromoperoxidase-like and iodoperoxidase-like activity. The MoS2 particles exhibited the highest Vmax value of 83 µM/s (H2O2 as substrate), remarkably superior to haloperoxidase and other haloperoxidase-like reported so far. The underlying mechanism of the iodoperoxidase mimics is oxygen vacancies. The iodoperoxidase-like can catalyze the oxidization of iodide ions (I−) by H2O2 to iodic acid (HIO3), which further enables to readily oxidize colorless 3,3’,5,5’-tetramethylbenzidine to green ox-TMB. Significantly, among the halogen anions (Cl−, Br− and I−), only I− was found to cause this oxidation reaction to occur. Thereafter, a fast, selective and cost-effective colorimetric detection of I− ion was developed with the linear range of 0.5–70 μM and detection limit of 292 nM (3σ/S). Further, the as-developed assay was applicable to detect seawater and human urines samples with satisfactory recoveries and accuracy. Thus the colorimetric assay based on MoS2 particles with haloperoxidase-like activity show great promise for I− sensing in environmental analysis and biochemical analysis.