Surface Enrichment in Au–Ag Alloy Nanowires and Investigation of the Dealloying Process

The fabrication of nanowires by electrodeposition of Au−Ag alloy into the pores of etched ion track polymer membrane is presented. The crystallinity, morphology, and composition of wires with diameters of 85, 45, and 30 nm are investigated by means of X-ray diffraction, high-resolution scanning transmission electron microscopy, and energy-dispersive X-ray analysis. Energy-dispersive X-ray analysis with very high spatial resolution (below 1 nm) reveals the presence of surface enrichment. A Ag-rich layer in Au40Ag60 wires and a Au-rich layer in Au60Ag40 wires with thicknesses between 1 and 4 nm are observed. After dealloying in nitric acid, Ag-rich wires exhibit porous morphologies whereas Au-rich wires remain solid cylinders. The results clearly indicate that the analyzed AuAg alloy nanowires do not consist of homogeneous solid solution, but surface effects before and during the dealloying play an important role for the final morphology of dealloyed nanowires.