Green synthesis of Cu-Doped ZnO nanoparticles using Syzygium cumini leaf extract and their antimicrobial evaluation

Abstract

Synthesis of nanoparticles by the green synthesis approach using the plant leaves extract has gained popularity since they are thought to be cost-effective, efficient and environment-friendly. This study was designed to synthesize copper-doped zinc oxide nanoparticles from Syzygium cumini leaf extract via the green approach. The nanoparticles formed of pure zinc oxide and copper doped zinc oxide were confirmed by Ultraviolet–Visible Spectroscopy (UV–Vis) is sharp absorption spectra at 378 (nm) and 383 nm. Using a zeta size study, the average size of biosynthesized pure ZnO and copper-doped ZnO nanoparticles was 78 and 86.07 nm and zeta potentials of -16.9776 and -28.38 milivolt(mV). Using Fourier Transform Infrared Spectroscopy (FTIR) analysis, peaks of the bioactive compounds and bond stretching of Syzygium cumini leaf extract were identified. Strong zinc oxide lattice vibrations of biosynthesized pure zinc oxide and copper-doped zinc oxide nanoparticles were found between 500–600 reciprocal centimeter (cm −1 ). X-ray Diffraction (XRD) analysis revealed characteristic diffraction peaks of pure ZnO at 2θ values of 36.44, 63.03, 68.12, and 69.29, whereas Cu-doped ZnO exhibited slightly shifted peaks at 36.29, 62.89, 67.98, and 69.07, confirming the retention of the hexagonal wurtzite structure after copper incorporation. The average surface roughness obtained from Atomic Force Microscopy (AFM) analysis was 2.093 for pure ZnO while for copper doping reduced to 1.824 nm. The synthesized Cu-doped ZnO nanoparticles exhibited enhanced antimicrobial activity against both bacterial and fungal pathogens, producing maximum inhibition zones of 19.99 ± 0.7 against Xanthomonas campestris and 28.37 ± 0.7 mm against Clavibacter michiganensis at the highest tested concentration. The findings demonstrated that the copper-doped zinc oxide nanoparticles exhibited lesser antimicrobial activity than the synthetic antibiotic but greater antimicrobial activity than S. cumini extract. Therefore, copper-doped zinc oxide nanoparticles synthesized by S. cumini leaf extract could be a promising candidate for antimicrobial applications.