The synthesis of metal oxide nanoparticles with the use of medicinal plant extract is a promising alternative to the conventional chemical method. This work aimed to synthesize zinc oxide nanoparticles using a green approach from indigenous “Koseret” Lippia adoensis leaf extract which is an endemic medicinal plant and cultivated in home gardens of different regions of Ethiopia. The biosynthesized zinc oxide nanoparticles were characterized using thermogravimetric analysis, X-ray diffraction, scanning electron microscopy-energy dispersive spectroscopy, transmission electron microscopy, ultraviolet-visible spectroscopy, and Fourier transform infrared spectroscopy. Furthermore, this study also evaluated the antibacterial activity of the synthesized ZnO nanoparticles against clinical and standard strains of Escherichia coli, Klebsiella pneumonia, Staphylococcus aureus, and Enterococcus faecalis by the disc diffusion method. According to the result of this study, ZnO nanoparticles synthesized using Lippia adoensis leaf extract showed promising result against both Gram-positive and Gram-negative bacterial strains with a maximum inhibition zone of 14 mm and 12 mm, respectively, using uncalcinated form of the synthesized ZnO nanoparticles.

Development of green technology is generating interest of researchers towards ecofriendly and low-cost methods for biosynthesis of nanoparticles (NPs). In this study, copper oxide (CuO) NPs were synthesized using a copper nitrate trihydrate precursor and Catha edulis leaves extract as a reducing and capping agent during the synthesis. The biosynthesized CuO NPs were characterized using an X-ray diffractometer (XRD), scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS), transmission electron microscope (TEM), Ultraviolet visible spectroscopy (UV-Vis), and Fourier transform infrared (FTIR) spectroscopy. XRD characterization confirmed that the biosynthesized CuO NPs possessed a good crystalline nature which perfectly matched the monoclinic structure of bulk CuO. Furthermore, the results obtained from SEM and TEM showed that the biosynthesized CuO NPs were spherical in shape. EDS characterization of the biosynthesized NPs also indicated that the reaction product was composed of highly pure CuO NPs. Moreover, the antimicrobial activities of different concentrations of CuO NPs synthesized using Catha edulis extract were also tested. Accordingly, the result showed that the highest zone of inhibitions measured were for CuO NPs synthesized using 1 : 2 ratios at 40 mg/ml solution concentration and observed to be 22 ± 0.01 mm, 24 ± 0.02 mm, 32 ± 0.02 mm, and 29 ± 0.03 mm for S. aureus, S. pyogenes, E. coli, and K. pneumonia, respectively.

Biogenic methods of synthesis of nanoparticles (NPs) using plant extracts have been given a great attention due to its nontoxicity and environmental friendliness. In this study, TiO2 NPs were synthesized from titanium tetrabutoxide and extract of root of Kniphofia foliosa. NPs of TiO2 were biosynthesized at different volume compositions of titanium tetrabutoxide to the plant extract with a ratio of 1 : 2, 1 : 1, and 2 : 1, respectively. These green synthesized NPs of TiO2 were characterized by thermogravimetric analysis (TGA/DTA), X-ray diffraction (XRD), scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS), transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-Vis), and Fourier transform infrared (FTIR) spectroscopy. TGA/DTA analysis has confirmed that the synthesized NPs of TiO2 were stable above the temperature of 500°C. The sharp and intense peaks at 2θ values of 25.3, 38.0, 47.9, 53.2, 54.8862, 62.7, 70.2, and 75.0 have confirmed formation of crystalline NPs of TiO2 in the sample of 1 : 1 and 2 : 1 ratios, and less crystalline samples for TiO2 NPs prepared in a 1 : 2 ratio. Comparison between FT-IR absorption bands of the plant extract and that of calcined NPs of TiO2 confirmed the purity of synthesized nanomaterials, except unavoidable adsorption of moisture on the surface of TiO2 NPs in an open air. The antibacterial activity of biosynthesized TiO2 NPs and that of ethanolic root extract of Kniphofia foliosa was investigated via the disc diffusion method against human pathogen bacteria strains of Staphylococcus aureus, Escherichia coli, Klebsiella pneumonia, and Streptococcus pyogenes. Among the different ratios, TiO2 (1 : 1) NP shows better performance towards Gram-negative bacteria due to its smaller average crystalline size and uniform morphology observed in SEM image relative to the other two ratios of TiO2 NPs. Antibacterial activity of the ethanolic root extract of Kniphofia foliosa itself showed better performance towards Gram-negative bacteria than NPs of TiO2 that might be due to antibacterial activity of residue of ethanol left with the plant extract.

This study presents the simultaneous exfoliation and modification of heterostructured copper oxide incorporated sulfur doped graphitic carbon nitride (CuO@S-doped g-C3N4) nanocomposites synthesized via chemical precipitation and pyrolysis techniques.

The current studies presented the green synthesis of zinc oxide and copper doped ZnO nanoparticles (NPs) using different ratios of Neem leaf extract and its antibacterial application on drug-resistant bacteria. The synthesized NPs were characterized using: X-ray diffractions (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscope (SEM), UV–visible spectroscopy and a simultaneous DTA-TGA thermal analyzer. All the synthesized materials were stable above 400°C. The powder diffraction studies indicated the formation of phase pure materials with wurtzite structure for pure ZnO and 0.5%, 1%, 1.5% Cu doped ZnO with the crystallite size in the range of 16.07 – 23.74 nm. SEM analysis revealed the formation of spherical shaped NPs with large grain size for 10% (v/v) ratio of aqueous leave extract. The aqueous extract of neem act as capping agent and prevent the NPs from agglomeration. The spectral studies confirmed the formation of NPs with the absorbance peak that is different from the micro-size ZnO. The antibacterial activities of the synthesized materials ZnO (1:1) against Staphylococcus aureus and uncalcined ZnO (7:3) and (Zn0.985Cu0.015O) against Bacillus subtilis were enhanced when referenced to the standard gentamicin.