Green Synthesis of CuO Nanostructures using Syzygium guineense (Willd.) DC Plant Leaf Extract and Their Applications

The medicinal plant, Syzygium guineense (Willd.) DC (Waterberry) mediated green copper oxide nanostructures (SyG-CuO NSs) were successfully synthesized for the first time in Ethiopia. The antibacterial activity of CuO NSs capped by biomolecules of the plant leaf extract has been investigated. The UV-visible, UV-DRS, FT-IR, XRD, TGA-DTA, SEM, EDXA, TEM, HRTEM and SAED techniques were employed to characterize the NSs. The presence of two absorbance maxima, λmax1 and λmax2 at 423 nm and 451 nm, respectively confirms a mixture of copper oxide (Eg=1.93 eV). FTIR spectra confirmed the presence of biomolecules with SyG-CuO NSs. The XRD patterns of NSs confirmed the presence of CuO with high crystallinity. The purity of the NSs was confirmed by SEM-EDAX analysis. In addition, TEM-HRTEM-SAED analysis revealed the d-spacing value of 0.2854 nm which corresponds to CuO (111) lattice fringe. SyG-CuO NSs showed good antibacterial effect against both Gram-positive bacteria, S. aureus (12 mm), and Gram-negative bacteria, E. coli (12 mm), P. aeruginosa (10 mm), and E. aerogenes (12 mm). The bioactive compounds capped around the CuO NPs served the effective role in disrupting the cell wall of bacterial strains. The CV and EIS studies confirmed the better electrochemical properties for SyG-CuO with low charge transfer resistance value of 49 Ω. These CuO NSs exhibited multifunctional applications.