Au Core/Au–Ag Alloy Shell Nanorods: Composition- and Shape-Tailored Optical Responses

Abstract

A feasible way is developed to prepare Au core/Au-Ag alloy shell nanorods (Au@Au(x)Ag(1-x) NRs) based on co-reduction of gold and silver ions under the guidance of Au NRs templates. Alloy nanorods with a wide composition range (x tunable from 0 to 1) are obtained. The Ag+/Au3+ ratios are found to affect the detailed morphology of the endcaps, which is responsible for the abnormal red-shift of localized surface plasmon resonance (SPR) mode. In consensus with theoretical prediction, dielectric sensitivity of the alloy NRs is mainly determined by the maximum of the LSPR band. Due to the change in electron structure, the alloy shells exhibit lower SERS activities than pure Ag shell.