Fabrication of copper oxide nanoparticles via microwave and green approaches and their antimicrobial potential

In the present work, copper oxide nanoparticles (CuO-NPs) were fabricated using two approaches, namely microwave irradiation (CuO(M)-NPs) and the green synthesis approach (CuO(G)-NPs). Their phase, purity, and structural parameters were confirmed using X-ray diffraction (XRD), and Rietveld refinement gave an average crystallite size ranging between 17 and 12 nm. Raman analysis indicated the peak shift toward a lower wavenumber in CuO (G)-NPs, attributed to a decrease in particle size due to the addition of Zanthoxylum armatum plant extract. Transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE-SEM) micrographs revealed the morphology with well-defined grain boundaries for CuO(G)-NPs, while diffused grains were observed for CuO (M)-NPs synthesized without the use of plant extract indicating that the plant extract restricted the agglomeration of CuO-NPs. X-ray photoelectron spectroscopy (XPS) showed chemisorbed species on the surface of CuO (G)-NPs, which, in turn, influenced their antimicrobial activity. Although no difference in the optical bandgap of both NPs is noticeable, the absorption intensity was higher for CuO (G)-NPs. Thermogravimetric analysis (TGA) corroborated XPS findings as it revealed that CuO (G)-NP sample underwent more weight loss as the temperature increased owing to the adsorption of organic moieties. The antimicrobial activity of both samples was also evaluated using different pathogenic bacteria and yeast strains: Bacillus subtilis, Escherichia coli and Candida albicans . The highest zone of inhibition of 23.0 ± 0.5 mm was observed for B. subtilis . The present study exhibited a swift and low-temperature protocol to enhance the antimicrobial performance of the CuO-NPs. The utilization of Z. armatum has the added advantage that nanotechnology processing industries can use this plant.