Abstract

Hierarchical copper oxide (CuO) microspheres were prepared by Moringa oleifera (M. oleifera) leaf extract assisted green synthesis method. The structural, chemical, and morphological features of the hierarchical CuO micro spheres were inspected by XRD, FTIR, SEM, and EDAX techniques. The XRD pattern unveiled the formation of monoclinic crystal structured CuO, which confirmed the conversion of Cu(NO3)(2 center dot)3H(2)O to Cu2+ ions by phytochemicals present in the M. oleifera leaf extract. The SEM micrographs demonstrated that small CuO nano structures have interacted with adjacent CuO nanostructures leading to the formation of cluster-like morphologies that resemble hierarchical CuO microspheres. The asymmetric stretching deformation vibration bands observed in the FTIR spectrum of the hierarchical CuO microspheres correspond to Cu-O bond along the (-2 0 2) direction that conveyed monoclinic unit crystal formation of the CuO. The detected Cu and O elements through the EDAX analysis reveal the pristine nature of the hierarchical CuO microspheres. The rich phytochemicals in the M. oleifera leaf extract played crucial roles towards the formation and stabilization of hierarchical CuO microspheres. The highest bactericidal activity was noticed against the Staphylococcus aureus strain with zone of inhibition (ZOI) of 30 and 32 mm for the hierarchical CuO microspheres dosage of 50 and 100 mu L, respectively, followed by Klebsiella pneumoniae, Escherichia coli and Bacillus cereus strains. The better bactericidal activity observed against the selected bacterial strains could be credited to ideal interaction of the hierarchical CuO microspheres/small nanostructures with cell walls of the bacterial strains, favorable deliverance of copper ions inside the cells and subsequent production of reactive oxygen species.