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.

CuO–ZnO nanocomposites (NCs) were synthesized using an aqueous extract of Verbascum sinaiticum Benth. (GH) plant. X-ray diffraction (XRD), spectroscopic, and microscopic methods were used to explore the crystallinity, optical properties, morphology, and other features of the CuO–ZnO samples. Furthermore, catalytic performances were investigated for methylene blue (MB) degradation and 4-nitrophenol (4-NP) reduction. According to the results, CuO–ZnO NCs with 20 wt % CuO showed enhanced photocatalytic activity against MB dye with a 0.017 min –1 rate constant compared to 0.0027 min –1 for ZnO nanoparticles (NPs). Similarly, a ratio constant of 5.925 min –1 g –1 4-NP reductions was achieved with CuO–ZnO NCs. The results signified enhanced performance of CuO–ZnO NCs relative to ZnO NPs. The enhancement could be due to the synergy between ZnO and CuO, resulting in improved absorption of visible light and reduced electron–hole (e – /h + ) recombination rate. In addition, variations in the CuO content affected the performance of the CuO–ZnO NCs. Thus, the CuO–ZnO NCs prepared using V. sinaiticum Benth. extract could make the material a desirable catalyst for the elimination of organic pollutants.

this work reveals a green combustion route for the synthesis of tio 2 , fe 2 o 3 and tio 2 -fe 2 o 3 nanocomposites as photocatalysts for decolorization of titan Yellow (tY) and Methyl orange (Mo) dyes at room temperature in aqueous solution concentration of 20 ppm under UV-light irradiation. We observed that the tio 2 -fe 2 o 3 nanocomposite shows superior photocatalytic activity for tY dye compared to pure tio 2 and fe 2 o 3 . Rate constant (k) values of tio 2 , fe 2 o 3 and tio 2 -fe 2 o 3 for tY and Mo are 0.0194, 0.0159, 0.04396 and 0.00931, 0.00772 0.0119 kmin −1 respectively. the surface area and pore volume of tio 2 -fe 2 o 3 nanocomposite were found to be 71.56 m 2 /g and 0.076 cm 3 /g, respectively as revealed by Bet studies. from the Barrett-Joyner-Halenda (BJH) plot, the mean pore diameter of tio 2fe 2 o 3 nanoparticles was found to be 2.43 nm. Further, the TiO 2 -fe 2 o 3 nanocomposite showed good electrochemical behavior as an electrode material for supercapacitors when compared to pure tio 2 and fe 2 o 3 nanoparticles resulted in stable electrochemical performance with nearly 100% coulombic efficiency at a scan rate of 10 mV/s for 1000 cycles. Interestingly, the novelty of this work is that the designed supercapacitors showed stable electrochemical performance even at 1000 th cycle, which might be useful for rechargeable supercapacitor applications. the electrochemical properties of the nanocomposites were compared by the data obtained by cyclic voltammograms, charge-discharge tests and electrochemical impedance spectroscopic studies. these results demonstrated that the tio 2fe 2 o 3 nanocomposite showed stable performance compared to tio 2 and fe 2 o 3 nanoparticles at current density of 5 Ag −1 .Recently electrochemical studies have gained significant attention due to energy and environment related issues. Since the discovery of TiO 2 and its applications as photo-anode for battery, splitting of water, supercapacitor, dye removal etc 1 ., many different metal oxides and electrodes have been explored to enhance the energy conversion efficiency. Amongst a variety of semiconductor metal oxides, hematite (α-Fe 2 O 3 ) was found to be a good anode material for supercapacitor application, which could be attributed to its high solar-to-hydrogen efficiency, encouraging optical band gap (~2 eV), outstanding chemical strength as well as ease of availability in the nature. However, α-Fe 2 O 3 exhibits low experimental performance compared with the theoretical values, which is possibly due to poor conducting and oxygen evolution properties in addition to short whole diffusion length. To overcome these problems, various synthetic methods have been tried in the recent past, to improve the experimental performance of α-Fe 2 O 3 .But, solution-based combustion method is a simple, low cost, energy saving, easy to control the surface morphology and particle size 2 . In addition, the materials prepared in this method are organic solvent free as we used water as solvent 3-5 .

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