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

Metal\noxide core–shell nanocomposites can derive bifunctionality\nfrom combining two or more intimately coupled domains of different\ndimensional nanomaterials. These properties can be tuned by adjusting\nthe composition and reaction conditions to modulate the structure–function\nrelationship. However, the colloidal synthesis of metal oxide 0D nanomaterials\nincorporated into 2D core–shell platelet nanostructures and\ntheir related applications remain underexplored. Effects of coupling\n0D nanoparticles and 2D plate-like structures may manifest via magneto-plasmonic\ninteractions. Here, we present a single-step method to synthesize\nplatelet-like ZnO nanostructures with a tunable layer structure and\na magnetic core. The uniqueness of this strategy lies in the use of\na magnetic iron oxide core, which seeds the lateral growth of hexagonal\nzinc oxide (ZnO) platelets, forming a 0D/2D core–shell heterostructure\n(henceforth denoted as Fe<sub><i>x</i></sub>O<sub><i>y</i></sub>@ZnO). Upon combining magnetic iron oxide with semiconducting\nZnO, the coercivity of Fe<sub><i>x</i></sub>O<sub><i>y</i></sub>@ZnO significantly increased compared to that of\npure iron oxide. We also employed magnetic force microscopy (MFM)\nto measure the magnetization distribution within the Fe<sub><i>x</i></sub>O<sub><i>y</i></sub>@ZnO domain. Magnetic\ncircular dichroism (MCD) spectroscopy was employed to characterize\nthe magneto-optic (MO) response of the material, showing significant\ndifferences between iron oxide alone vs core–shell nanoplatelets\nof different morphologies. The systematic approach to synthesizing\ncore–shell nanoplatelets of tunable size and morphology holds\ngreat promise in practical applications, especially in applications\nin which both optoelectronic and magnetic properties are of interest.