Fully alloyed Ag/Au nanorods with tunable surface plasmon resonance and high chemical stability

Limited success has been achieved in preparing nanorods of silver with uniform sizes and tunable localized surface plasmon resonances. Also, the practical applications of silver nanostructures have been hindered by their poor chemical stability in a corrosive environment. Here we address these issues by converting Au@Ag core/shell nanorods into fully alloyed ones through controlled high-temperature annealing in confined spaces. Compared with their core/shell counterparts, the obtained alloy nanorods demonstrated significantly enhanced stability toward oxidative etching. We also systematically investigated their novel plasmonic properties, and revealed that the band positions of both longitudinal and transverse modes can be readily tuned by either manipulating the Ag/Au ratio or starting with gold cores of different aspect ratios. Moreover, we have achieved widely adjusted peak intensity ratios between the transverse and longitudinal bands from 0.14 to 1.22, which is impossible for nonalloyed nanorods. The alloy nanorods developed in this work are believed to find great uses in fundamental spectroscopic studies as well as many attractive plasmonic applications.