Catalytic reduction and antibacterial study of Ag–Cu bimetallic alloy nanoparticles: effect of precursor sequencing on structural, morphological and functional behavior

This work investigates the influence of precursor sequencing on the formation and surface/interfacial properties of Ag Cu bimetallic nanoalloys synthesized by wet chemical reduction under inert atmosphere. Three synthesis routes (Ag Cu, Cu Ag, and simultaneous addition “AgCu-Simu”) were employed to control nucleation and growth processes, enabling systematic tuning of particle size, surface composition, and interfacial heterogeneity. Structural and surface-sensitive analyses (XRD, XPS, Zeta potential, FTIR, SEM, HR-TEM and STEM–EDS) indicate the formation of alloyed Ag Cu nanoparticles with route-dependent differences in morphology and near-surface composition. Notably, the simultaneous metal addition route yields ultrasmall (~15 nm), highly dispersed nanoparticles with a Cu-enriched and chemically heterogeneous surface. These interfacial characteristics strongly influence functional performance, leading to enhanced catalytic and antibacterial activity. The AgCu-Simu sample exhibits rapid reduction of methylene blue and methyl orange within 4 and 6 min, respectively, under low catalyst loading, following pseudo-first-order kinetics, and shows the highest antibacterial activity with inhibition zones of 23 mm ( E. coli ) and 30 mm ( L. monocytogenes ). The improved performance is attributed to the synergistic interplay between Ag and Cu and the presence of reactive metal–oxygen interfacial sites that facilitate adsorption and electron transfer. Overall, this study demonstrates that precursor sequencing is a simple yet effective strategy to engineer surface and interfacial properties of Ag Cu nanoalloys, providing new insight into structure–surface–function relationships relevant for catalytic and antimicrobial applications.