Gold coating of silver nanoprisms

Abstract

Core-shell Ag@Au nanoprisms are prepared through a surfactant-free seed-mediated approach by taking advantage of the anisotropic structure of silver nanoprisms as seeds. The gold coating on the silver nanoprism surface is achieved by using hydroxylamine as a mild reducing agent, and the final fully gold-coated prism structures are confirmed by microscopic and spectroscopic characterization. The resulting Ag@Au core-shell structure preserves the optical signatures of nanoprisms and offers versatile functionality and particularly better stability against oxidation than the bare silver nanoprism. The surface plasmon resonances of the core-shell Ag@Au nanoprisms can be tuned throughout the visible and near-IR range as a function of the Au shell thickness. Such tailorable optical features and surfactant-free gold shells have great potential applications in biosensing and bioimaging. Core-shell Ag@Au nanoprisms are successfully synthesized through a surfactant-free seed-mediation approach by direct gold coating of silver nanoprisms with controllable Au shell thickness. The clean gold shell surface and tunable surface plasmon resonance of these core-shell nanoprisms enable straightforward further functionalization for a variety of applications. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.