Self-assembly driven morphological evolution of CuO nanostructures: Electronic, optical and magnetic characterization

We explore the self-assembly induced morphological evolution of CuO nanoparticles using two different synthesis methods. In direct solution phase, the CuO nanoparticles self-assemble and form mesocrystals, adopting ellipsoidal and sheet like morphology, depending on the initial precursor concentration. However, mesocrystal formation is not observed in an alternative route, wherein annealing of the precipitate obtained after mixing the precursor solutions at 300 °C yield agglomerated nanoparticles and nanorods. Based on the morphological analysis, the formation mechanism under the two synthesis methods is proposed. The effect of morphology on the surface electronic structure, optical and vibration characteristics is investigated by X-ray photoelectron spectroscopy, optical absorption spectroscopy and Raman spectroscopy, respectively. Optical absorption spectra show distinct changes in the band gap relative to nanostructure morphology. DC magnetization measurements reveal signs of antiferromagnetic ordering in CuO nanomaterials, and also a strong correlation between the size of the constituents of mesocrystals and the antiferromagnetic ordering temperatures.