Synthesis and Characterization of Ferromagnetic Fe3O4–ZnO Hybrid Core–Shell Nanoparticles

Room-temperature synthesis of multifunctional core–shell nanostructures with iron oxide (Fe3O4) core and zinc oxide (ZnO) shell is described. High-resolution transmission electron microscopy revealed the occurrence of heteroepitaxial growth of a ZnO shell over the iron oxide nanoparticle core. The formation of the core–shell nanostructure was also evidenced by x-ray diffraction and x-ray photoelectron spectroscopy analyses. The core Fe3O4 nanoparticles exhibited superparamagnetic behavior at room temperature in an externally applied magnetic field. However, magnetic measurements of the core–shell nanoparticles revealed ferromagnetic behavior, originating from defect-induced ferromagnetism in the ZnO shell. The prepared core–shell nanoparticles also exhibited strong photoresponse while retaining ferromagnetic behavior at room temperature.