Tunable fabrication on iron oxide/Au/Ag nanostructures for surface enhanced Raman spectroscopy and magnetic enrichment

Abstract

A facile approach was developed to prepare novel multifunctional Fe2O3/Au/Ag nanostructures integrated with isolated functions involving magnetic and optical properties. The Fe2O3/Au/Ag hybrid nanoparticles with different thicknesses of Ag shell were prepared by adjusting the amount of the AgNO3. Surface structures were varied from the rough with pinhole to smooth and pinhole free surfaces with increasing amounts of AgNO3. The surface plasmon resonance was tuned in a very wide region from that of Au to Ag. Surface enhanced Raman scattering (SERS) effects were also investigated, employing thiophenol (TP) and aminothiophenol (PATP) as probe molecules. It was revealed that the SERS intensity was strongly depended on the molar ratio of Ag and Au. With an increase in the Ag molar fractions, SERS signals were enhanced to the maximum due to the surface plasmon resonance of the pinhole structure. The magnetic enrichment for on line SERS monitoring the molecules with low concentration was performed based on the magnetic core and the SERS activity of the bimetallic shells. This enrichment procedure improved efficiently the limits of the SERS detection. It was shown that the multicomponent nanoparticles have potential applications in the fields of optical devices and magnetic separation.