Magnetic Iron Oxide Seed-mediated Formation of 2D ZnO Core–shell Nanostructures

Metal oxide core–shell nanocomposites can derive bifunctionality from combining two or more intimately coupled domains of different dimensional nanomaterials. These properties can be tuned by adjusting the composition and reaction conditions to modulate the structure–function relationship. However, the colloidal synthesis of metal oxide 0D nanomaterials incorporated into 2D core–shell platelet nanostructures and their related applications remain underexplored. Effects of coupling 0D nanoparticles and 2D plate-like structures may manifest via magneto-plasmonic interactions. Here, we present a single-step method to synthesize platelet-like ZnO nanostructures with a tunable layer structure and a magnetic core. The uniqueness of this strategy lies in the use of a magnetic iron oxide core, which seeds the lateral growth of hexagonal zinc oxide (ZnO) platelets, forming a 0D/2D core–shell heterostructure (henceforth denoted as Fe_xO_y@ZnO). Upon combining magnetic iron oxide with semiconducting ZnO, the coercivity of Fe_xO_y@ZnO significantly increased compared to that of pure iron oxide. We also employed magnetic force microscopy (MFM) to measure the magnetization distribution within the Fe_xO_y@ZnO domain. Magnetic circular dichroism (MCD) spectroscopy was employed to characterize the magneto-optic (MO) response of the material, showing significant differences between iron oxide alone vs core–shell nanoplatelets of different morphologies. The systematic approach to synthesizing core–shell nanoplatelets of tunable size and morphology holds great promise in practical applications, especially in applications in which both optoelectronic and magnetic properties are of interest.