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

Abstract

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 Ag₃₃Au₆₇ 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.