Interfacial Engineering of Cu-Au Core-Nanocluster Systems for Oxygen Reduction, Reactive Oxygen Species Generation, and Antimicrobial Activity

Cu-Au core-nanocluster nanoparticles (NPs) offer a promising platform for multifunctional antimicrobial materials through coupled oxygen reduction, reactive oxygen species (ROS) generation, and galvanically enhanced ion release. Here, the interfacial mechanisms governing antimicrobial activity in CuAux NPs are investigated using structural characterisation, density functional theory (DFT), electrochemical analysis, and antibacterial testing. SEM, TEM, XRD, and XPS confirm a Cu-Au core- nanocluster architecture comprising ~50 nm Cu NPs decorated with ~2-3 nm Au nanoclusters, generating abundant catalytic interfacial sites. DFT calculations reveal complementary roles for Cu and Au, whereby Cu promotes oxygen activation by reducing the O–O dissociation barrier to 0.189 eV, while Au stabilises partially reduced intermediates and favours selective two-electron oxygen reduction. Rotating ring-disk electrode measurements validate H2O2 generation, while chronoamperometry demonstrates stable electrochemical performance. Galvanic Cu2+ release reaches 2442.67 μg/mL (73.28% dissolution) under acidic conditions, with physical-mixture controls confirming the importance of intimate Cu-Au coupling. Antibacterial assays identify CuAu1.5 as the optimal composition, exhibiting the highest inhibition against E. coli (~1.0 cm) and S. aureus (~1.4-1.5 cm). The results establish a direct structure- property-performance relationship linking Cu-Au interfacial architecture to oxygen reduction, ROS generation, Cu2+ release, and antimicrobial activity, highlighting interfacial engineering as an effective strategy for antimicrobial nanomaterial design.