Green Synthesis and Characterization of Copper Oxide (CuO) Nanoparticles Using <i>Mesua ferrea</i> Leaf Extract and Evaluation of Biological Activities

Abstract The development of green technology has garnered substantial research attention as it offers inexpensive and eco‐friendly ways to synthesize nanoparticles. Here, we describe the alkaline hydrolysis approach used to create CuO Nanoparticles (CuO NPs) with Mesua ferrea extract present. FTIR, FESEM, XRD, zeta potential, DLS, EDX, and UV–vis analyses were performed to characterize the synthesized CuO NPs. With an average crystallite size of 32.31 nm for calcined CuO NPs and 18.57 nm for non‐calcined CuO NPs, the XRD technique demonstrated the monoclinic crystalline phase of the CuO NPs according to the JCPDS standard card no: 48‐1548. The FESEM images confirm the formation of nanoparticles with sizes lying in the 10–60 nm range and also show the spherical shape of the nanoparticles. The FTIR spectra indicated the formation of CuO NPs by showing bonds in 400 to 700 cm −1 range. The TGA and DTG curves show the thermal behavior of the synthesized CuO NPs. Zeta potential for the synthesized CuO NPs was found to be −33.4 and −61.9 mV, respectively. The UV–vis spectrophotometer gave the maximum absorbance in the 250–350 nm range, and the band gap energy of the synthesized CuO NPs was measured using the Tauc plot, and it was preferable for the allowed direct transition mode and found to be 2.502 and 1.99 eV, respectively. The maximum radical inhibition values were found to be 61.64% and 67.51% for calcined and non‐calcined CuO NPs in the DPPH assay, 52.37% and 79.43% in the ABTs assay, respectively. The produced CuO NPs antibacterial efficacy was investigated against one fungus, two gram‐positive, and two gram‐negative bacteria. In addition to being more sensitive to the two gram‐negative bacteria S. abony and Escherichia coli , the CuO NPs exhibit a larger zone of inhibition (16.8 ± 0.76 mm) to the gram‐positive bacteria Staphylococcus aureus .