Magneto-luminescent zinc/iron oxide core-shell nanoparticles with tunable magnetic properties

Core-shell nanospheres with tailorable magnetic properties and strong luminescence promise versatile and efficient biomedical and electronic applications. We report a low-cost sonochemical synthesis of ZnO/iron oxide core-shell nanostructures with tunable magnetic properties. The high-resolution transmission electron microscopy (HRTEM) illustrates the distinguished dispersity of the oxide nanoparticles, whereas elemental profiling using line scan data confirm the formation of the distinguished core and shell phases. Annealing in N2–H2 and Ar–H2 ambient alters the magnetic properties such as coercive field, saturation magnetization, and remnant magnetization within the inverse spinel iron oxide with space group Fd3m. Subtle structural changes between maghemite (γ-Fe2O3) and its reduced form, magnetite (Fe3O4), have been identified in the thin (0.5–3 nm) shell region of atomic dimensions. Structural composition including phase transitions and defect states are investigated using XRD, XPS, and Raman measurements. Coexistence of ferromagnetism (from the shell and characterized by magnetic measurements) and strong luminescence (from ZnO core and obtained from photoluminescence spectroscopy) at room temperature indicates exotic magneto-optical coupling, which is supported by the blue-shifted luminescence spectra. Our approach combining nanotechnology and solid-state chemistry opens a new frontier to the building of innovative nanomaterials for integration, especially multifunctional core-shell oxide nanomaterials.