Magnetic Fe2O3/Au core/shell nanoparticles can be particularly used in biological separation, but the development of an appropriate technique including a production process for higher efficient separation and the subsequent immunoassay for lower level still represent a great challenge. In this article, Fe2O3/Au core/shell nanoparticles with different Au ratios were prepared by reducing HAuCl4 on the surface of gamma-Fe2O3 nanoparticles. Scanning electron microscopy (SEM) images and surface-enhanced Raman spectroscopy (SERS) spectra clearly show that the surfaces of Fe2O3 nanoparticles were covered by Au. SERS signals of pyridine (Py) have been obtained on the Fe2O3/Au nanoparticles, and it has been found that the SERS intensity enhanced with the increase of iterative additions of HAuCl4. The antigens in test solution have been effectively separated by the magnetic Fe2O3/Au core/shell nanoparticles, and subsequent rapid detection was examined by immunoassay analysis based on SERS. The result demonstrates that the magnetic bioseparation program used by this magnetic Fe2O3/Au core/shell nanoparticles could separate almost all of the antigens in test solution. The ease of operation and good separation efficiency of this effective method has shown a potential application for magnetic Fe2O3/Au core/shell nanoparticles in bioseparation.
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 Au 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 103-104. 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.
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