Bio-synthesis of zinc oxide (ZnO) NPs using ruta chalepenusis leaf extract: its characterization and application as antibacterial

Abstract

The progress of green chemistry in the synthesis of NPs using plant extracts has attracted a great attention currently due to its low cost, simplicity of preparation, non-toxic and environmental friendly process. The synthesis of metal oxide NPs with the use of medicinal plant extract is a promising alternative to the conventional chemical method. This work aimed to synthesize ZnO NPs using different ratios by green approach from indigenous ―Tenadam,” Ruta chalepenusis leaf extract for antibacterial application which is an endemic medicinal plant and cultivated in home gardens of different regions of Ethiopia and other parts of the world. Zinc Nitrate hexahy drate was used as precursor to synthesize ZnO NPs using the Ruta chalepenusis leaf extracts. The biosynthesized ZnO NPs were characterized using, X-Ray Diffraction (XRD); Scanning Electron Microscopy (SEM), Ultraviolet-Visible Spectroscopy, and Fourier Transform Infrared Spectroscopy (FTIR). The XRD analysis reveals all the synthesized particles have hexagonal wurtizite structure of ZnO NPs with particle size in the range of 19.72– 27.40 nm. The SEM analysis indicated the porous, spherical shapes and having granular nature morphology for the samples that calcinated at 450 0C and grain size increases with the decrease of the concentration of the capping agents. The FT-IR analysis shows the interaction between the capping agents and the synthesized ZnO NPs which is also confirmed by SEM studies. The UV-Visible result showed the absorbance peak at 376 nm -410nm corresponding to the characteristic band of ZnO NPs. Furthermore, this study also evaluated the antibacterial activity of the synthesized ZnO NPs against standard strains of Staphylococcus aureus, and Escherichia coli, by the disc diffusion method. According to the result of this study, ZnO NPs synthesized using leaf extract of Ruta chalepenusis showed promising result against both Gram-positive and Gram-negative bacterial strains with a maximum inhibition zone of 22.67 mm and 12.00 mm, respectively, using the syn thesized ZnO NPs (1:1) ratio by volume from wet leaf extracts of Ruta Chalepenusis have better performance with the reference to the selected standards and Ceftriaxone