(80c) Iron-Assisted Growth of Anisotropic ZnO Nanostructures for Magnetic and Optical Applications

Doping of zinc oxide nanocrystals with magnetic elements is of interest for achieving tunable magnetic, optical and optoelectronic properties. In this study, we present three distinct examples of Fe-assisted growth of zinc oxide hexagonal nanostructures, including hexagonal nanoplatelets, truncated hexagonal pyramids, and hexagonal hand-shaped structures. Although each of these nanostructures adopts a different morphology, are all single-phase hexagonal wurtzite zinc oxide materials whose growth and properties are affected by the presence of Fe atoms. Systematically varying the composition and reaction conditions allowed us to tune their size and shape to reveal structure-property relationships. Both ambient temperature and low-temperature magnetization measurements revealed combinations of ferromagnetic, paramagnetic, and superparamagnetic behavior that varied with composition and morphology. Building upon the Fe-doped-zinc oxide motif, we simultaneously doped ZnO with the other magnetic elements such as Co and Ni. The co-doped materials showed strong magnetic circular dichroism (MCD) responses that varied in both magnitude and spectral structure with doping. This indicates that the level and type of dopants play an important role in determining the overall MCD response. Additionally, beyond doping with magnetic elements, introducing additional elements such as Ge, Ga, and In altered the MCD response. The Verdet constant, a measure of the strength of the Faraday effect in a nanostructure, was significantly enhanced by these additional elements. The type and level of doping not only introduced new dopant states but influenced the formation of defects in the nanostructures. This led to modifications in overall electronic structure, thereby contributing to the enhancement of the Verdet constant while also altering the optical absorption and emission spectra of the nanostructures Taking advantage of the high Verdet constant, these nanocomposites can be applied in future applications such as biomedical imaging and spectroscopy, as well as magneto-optical sensors.