Etched PtCu nanowires as a peroxidase mimic for colorimetric determination of hydrogen peroxide

Etched PtCu nanowires (NWs) were synthesized by a hydrothermal reaction and chemical etching process. The NWs are shown to be viable peroxidase (POx) mimics capable of catalyzing the oxidation of the substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H₂O₂ to form a blue-green coloration. The mechanism of catalysis was investigated and the results demonstrated that H₂O₂ is decomposed to form hydroxyl radicals which oxidize TMB in the presence of the NWs. Under optimized conditions, a steady-state kinetic analysis revealed that the NWs possess a stronger affinity for H₂O₂ and TMB compared to the enzyme horseradish POx. Based on the high POx-like activity, a colorimetric assay for H₂O₂ was established. Absorbance at 652 nm increases linearly in the 0.1-300 μM H₂O₂ concentration range, and the detection limit is 0.06 μM (at S/N = 3). The assay was successfully applied to the determination of H₂O₂ in (spiked) milk and contact lens solution. Furthermore, a highly sensitive test strip was designed which represents a low cost and fast alternative for the visual determination of H₂O₂. Graphical Abstract Schematic presentation of the colorimetric detection of H₂O₂. PtCu nanowires (PtCu NWs) can catalyze 3,3',5,5'-tetramethylbenzidine (TMB) oxidation by H₂O₂ to produce blue-green oxidized 3,3',5,5'-tetramethylbenzidine (oxTMB). Based on the color change, test strips were designed for H₂O₂ detection.