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 M H2O2 concentration range, and the detection limit is 0.06 M (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.