Synthesis and characterization of Au@Co and Au@Ni core-shell nanoparticles and their applications in surface-enhanced Raman Spectroscopy

Au@Co and Au@Ni core-shell nanoparticles with controllable shell thicknesses were prepared by reduction of Co2+ and Ni2+ salts with hydrazine hydrate in ethanol over preformed An seeds. Both cyclic voltammetric and surface-enhanced Raman studies using CO as the probe molecule confirmed the core-shell structure of the synthesized nanoparticles. The Au@Co and Au@Ni nanoparticles dispersed on a glassy carbon electrode surface exhibit high surface-enhanced Raman scattering (SERS) effect for the adsorbed pyridine. High-quality SERS spectra of CO absorbed on Co and Ni have been obtained through the high enhancement of the core-shell nanoparticles. The originally low surface enhancement of the Co and Ni can be substantially improved giving total enhancement factors up to 10(3)-10(4). Such a SERS-active substrate can be used as an alternative substrate for investigating adsorption and reactions occurring on the Co and Ni metal surfaces.