Anomalous Size-Dependent Selective Dissolution of Gold–Silver Alloy Nanoparticles Driven by Plastic Deformation

When alloy nanoparticles undergo leaching, the chemically active species, such as Ag in Au x Ag 1– x nanoparticles, dissolve rapidly, whereas the chemically noble species, e.g., Au, is left behind. Contrary to the common expectation that smaller metal nanoparticles will exhibit a higher rate of dissolution owing to their increased surface area-to-volume ratio, we find that large Au–Ag nanoparticles can dissolve faster than smaller ones. The underlying reason for this anomalous size-dependent behavior is that Ag dissolution in large nanoparticles creates gold-rich porous ligaments, which continuously undergo structural collapse driven by internal stresses. Plastic deformation of ligaments exposes fresh Ag from the interior, thus accelerating the dissolution process. Pore formation is absent in smaller nanoparticles ensuring temporary surface passivation, which explains the anomalous behavior.