The hot aqueous extract of E. camaldensis leaves as a degradable agent and copper nitrate as a copper source with cold plasma was used in this work to present an easy and green technique for copper oxide nanoparticles (CuO NPs) synthesis. UV-Vis absorption spectroscopy, X-ray diffraction (XRD), Atomic Force Microscopes (AFM), and Scanning Electron Microscopes (SEM) were all used to determine the production of copper oxide nanoparticles (SEM). The energy gap was 4.9[Formula: see text]eV, and the average crystalline size of CuO NPs evaluated using the Scherrer equation was 15.06[Formula: see text]nm, according to the X-ray diffraction pattern (XRD). CuO NPs had a grain size of 70.63 nanometers, according to AFM morphology study. Finally, the effect of copper oxide nanoparticles on Gram-positive and Gram-negative bacteria, as well as fungi, was studied.