Bio-inspired branched Au–Cu nanoalloys for achieving synergistic dual-pathway peroxidase-like activity

Abstract

In this study, we report a simple and green one-pot co-reduction strategy for the synthesis of bimetallic Au–Cu branched nanostructures under aqueous conditions. Curcumin was employed as both a reducing and stabilizing agent, eliminating the need for additional chemical reagents. The resulting Au–Cu nanoalloy exhibited a distinctive branched nanotubular morphology and demonstrated excellent peroxidase-like catalytic activity. The catalytic performance was evaluated using the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB), where the initially colourless substrate was converted into a blue-colored oxidized product. The system exhibited a detection limit of 8 µM for H₂O₂. Furthermore, steady-state kinetic parameters, including the Michaelis–Menten constant (K_m) and maximum reaction velocity (V_max), were determined by varying the concentrations of substrates (H₂O₂ and TMB). The low K_m value obtained for TMB indicates a strong affinity of the Au–Cu nanoalloy toward the substrate. A comparative analysis with the curcumin-stabilized gold nanoparticles revealed that the incorporation of copper significantly enhances the catalytic efficiency of the nanostructures. The electron transfer mechanism underlying the catalytic process was further validated using cyclic voltammetry and electrochemical impedance spectroscopy. Overall, this work presents an efficient multimodal sensing platform for the sensitive detection of H₂O₂.