One-Pot Controllable Synthesis of Au@Ag Heterogeneous Nanorods with Highly Tunable Plasmonic Absorption

It generally requires a complex workup procedure for the fabrication of Au@Ag heterogeneous nanostructures with an accurate morphology by the present multistep seed-mediated growth approaches. In this paper, we present a new and straightforward method for the controllable synthesis of uniform Au@Ag heterogeneous nanorods (NRs) by coreduction of gold and silver sources in a one-pot polyol reaction. High-quality Au@Ag heterogeneous NRs of various aspect ratios were facilely and selectively produced in high concentration by tuning the initial experimental parameters. Our synthetic approach is highlighted by its simplicity, large-scale production, and controllability of the synthesis. Our study indicates the oxidative etching by O-2/Cl- pairs plays a key role for the high yield synthesis of uniform Au@Ag heterogeneous NRs. The size dependent optical properties of Au@Ag heterogeneous NRs were first and systematically investigated Our experiments reveal that Au@Ag heterogeneous NRs exhibit two strong absorption peaks that, respectively, originate from the transverse and longitudinal localized surface plasmon resonances (LSPRs). Moreover, the longitudinal LSPR can be facilely tuned from the visible to the near-infrared regions by changing the aspect ratio of Au@Ag heterogeneous NRs. Importantly, Au@Ag heterogeneous NRs synthesized by our method have an excellent stability. They can maintain their optical properties over a long period of time. Au@Ag heterogeneous NRs with an interesting plasmonic property would have fascinating application in surface plasmonics, surface-enhanced Raman scattering, chemical and biological sensing, optical labeling, and information storage.