Synthesis and characterization of novel lanthanide-doped magnetite@Au core@shell nanoparticles

• LN:Fe3O4 were fabricated using lanthanide acetate and Fe(acac)3 as precursors.
• LN:Fe3O4@Au NPs were prepared by the reduction of Au on the surface of the core NPs.
• The engineered core@shell nanoparticles exhibit both magnetic and plasmonic properties.

Lanthanide (LN)-doped magnetite (Fe3O4) nanoparticles (NPs) were prepared initially as seeding materials, which was followed by the reduction of Au acetate on the surface of the core to produce LN: Fe3O4@Au core@shell NPs. The magnetite NPs were doped with gadolinium (Gd) and europium (Eu) to obtain Gd:Fe3O4 and Eu:Fe3O4, respectively. Transmission electron microscopy (TEM) revealed Gd:Fe3O4, Eu:Fe3O4, Gd:Fe3O4@Au, and Eu:Fe3O4@Au with mean diameters of 6.4, 5.7, 8.4, and 8.9 nm, respectively. X-ray photoelectron spectroscopy showed that Gd or Eu was present in the doped core NPs, respectively. TEM, X-ray diffraction and ultraviolet-visible spectroscopy showed that the core NPs were well coated with Au shells. The magnetic properties of the core NPs and core@shell NPs were characterized by recording the M-H and M-T curves. The magnetically engineered core@shell NPs may have potential bio-applications that may require both magnetic and plasmonic properties.