Formation of one-dimensional Ag–Au solid solution colloids with Au nanorods as seeds, their alloying mechanisms, and surface plasmon resonances

In this work, one dimensional (1D) Ag-Au solid solution nanoalloys were synthesized by rapidly diffusing Ag into the preformed Au nanorod (AuNR) seeds at ambient temperature in aqueous solution. By varying the molar ratio of AgCl/AuNR (in gold atoms), two kinds of 1D Ag-Au alloy nanostructures with a narrow size distribution--AgAu nanowires and Ag(33)Au(67) nanorods--could be obtained in high yields when NaCl and polyvinylpyrrolidone (PVP) were used as an additive and capping reagent, respectively. Based on HRTEM imaging combined with a series of control experiments, it is conceivable that vacancy/defect-motivated interdiffusion of Ag and Au atoms coupled with oxidative etching is a crucial stage in the mechanism responsible for this room-temperature alloying process, and the subsequent conjugation of the fused Ag-Au alloyed nanostructures is associated with the formation of the AgAu nanowires. The resulting 1D Ag-Au nanoalloys form stable colloidal dispersions and show unique localized surface plasmon resonance (LSPR) peaks in the ensemble extinction spectra.