Fabrication of Hierarchical CuO Microspheres

Abstract

Hierarchical microstructures of metal oxides comprised of nanoparticles, nanorods, and nanobelts as building blocks have been attracted great interests due to their novel structures, properties, and applications. In most systems, hierarchical assembly involves two distinct steps: 1) synthesizing the appropriate precursors, and 2) assembling them into larger structures. Copper oxide (CuO) is a narrow bandgap semiconducting oxide that has been widely used in electrochemical cells, in photothermal and photoconductive materials, and as a heterogeneous catalyst. Various techniques have been used to synthesize CuO nanostructures such as nanoparticles, nanorods, nanobelts, nanoribbons and nanotubes. However, the methods for fabricating CuO hierarchical microstructures were examined by a few groups. Dandelion-like CuO hollow microspheres have been synthesized by a solvothermal process. CuO microspheres have been generated by a simple solution method using sodium tartrate as a chelating agent and CuO whisker assemblies have been fabricated using a microwave-induced polyol process. Here we report a simple method for fabricating hierarchical CuO microspheres with an average diameter of 1.5-2.5 μm under the microwave irradiation. In this method, the CuO microspheres are built from small flakes, each comprised of several nanoplates of 15-25 nm wide and about 400 nm long. The effect of capping reagent concentration on the morphologies of the CuO products was also investigated.