Hierarchical ZnO Nanostructures

A variety of novel hierarchical nanostructures with 6-, 4-, and 2-fold symmetries have been successfully grown by a vapor transport and condensation technique. It was found that the major core nanowires are single-crystal In2O3 with 6, 4, and 2 facets, and the secondary nanorods are single-crystal hexagonal ZnO and grow either perpendicular on or slanted to all the facets of the core In2O3 nanowires. The core In2O3 nanowires have diameters of about 50−500 nm, whereas the secondary ZnO nanorods have diameters of about 20−200 nm. Depending on the diameter of the core In2O3 nanowires, the secondary ZnO nanorods grow either as a single row or multiple rows. These hierarchical heteronanostructures may find applications in a variety of fields such as field emission, photovoltaics, transparent EMI shielding, supercapacitors, fuel cells, high strength and multifunctional nanocomposites, etc. that require not only high surface area but also structural integrity.