Synthesis method, antibacterial and photocatalytic activity of ZnO nanoparticles for azo dyes in wastewater treatment: A review

Copper oxide nanoparticles (CuO-NPs) were synthesized using two different methods (chemical and biosynthesis) to study the influence of the preparation method on the structural, optical, morphological, photocatalyst, antibacterial and in vitro antioxidant of these nanoparticles. The synthesized nanoparticles were analysed by XRD, UV–Vis, HR-TEM, DLS, ZE, PL and FT-IR spectroscopy. The X-ray diffraction spectra showed the single-phase monoclinic structure of copper oxide, with an average crystallite size of 2.05–3.00 nm. HR-TEM analysis confirmed the spherical morphology of the synthesized CuO-NPs using chemical and biological methods with an average size of 32 nm and 25 nm, respectively. The synthesized CuO-NPs exhibited potential photocatalytic activity towards the degradation of methylene blue dye on exposing to sunlight irradiation. The degradation effectiveness against methylene blue dye was found to be 85 and 97% for chemical and biosynthesized CuO-NPs, respectively. Furthermore, antibacterial and antioxidant activities were evaluated. The biogenic method showed a significant antibacterial activity against Gram-negative bacteria E. coli and B. subtilis than Gram-positive bacteria and also DPPH assay.

Synthesis of copper oxide nanoparticles by chemical and biogenic methods: photocatalytic degradation and in vitro antioxidant activity

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.

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Synthesis of Zinc Oxide Nanoparticles Using Leaf Extract of Lippia adoensis (Koseret) and Evaluation of Its Antibacterial Activity

Textile wastewater comprises a complex mixture of chemical substances and dyes such as disperse dyes which have a high potential as carcinogenic, mutagenic, and teratogenic. Textile wastewater effluent contributes 20% of the water pollution with a high contribution to environmental contamination, where about 50,000 tons/year of dyes are dumped into the environment. The advanced oxidation processes (AOPs), which includes photocatalytic degradation (PD) using nanophotocatalysts, is a rising technology causing in completing the mineralization of the dyes, compared to traditional treatment techniques such as the absorption method, which transfers the pollutants to other stages. Photolysis is capable of partially degrading 50 to 80% of micro-pollutants like dyes using nanophotocatalysts. The literature indicates that about 70 to 80% of studies use photocatalysis using ZnO/TiO2 as a photocatalyst in wastewater treatment. However, the photocatalysts used have limited potential for removing dyes from textile wastewater. Thus, it is urgent to improve the ZnO NPs synthesis to maximize the PD efficiency to degrading textile wastewater dyes. The present review focuses on exploring the efficiency and mechanism of the photodegradation of textile wastewater dyes using zinc oxide nanoparticles (ZnO NPs) synthesized in the plant extract. The highest photolysis efficiency was found at low dye concentrations and pH to improve the initial operating parameters. Photolysis increases with increasing photocatalysis in the surface area and with an optimum amount of photocatalyst. Furthermore, appropriate photoirradiation is also necessary to conduct the photocatalytic process at room temperature. 

Photocatalytic degradation of disperse azo dyes in textile wastewater using green zinc oxide nanoparticles synthesized in plant extract: A critical review

Recent advances on botanical biosynthesis of nanoparticles for catalytic, water treatment and agricultural applications: A review.

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.

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Synthesis of Copper Oxide Nanoparticles Using Plant Leaf Extract of Catha edulis and Its Antibacterial Activity

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.

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Synthesis of Titanium Oxide Nanoparticles Using Root Extract of Kniphofia foliosa as a Template, Characterization, and Its Application on Drug Resistance Bacteria

The large-scale production of high-quality graphene is the major focus of scientists and engineers recently. However, its massive manufacturing routes from its precursor graphene oxide (GO) are involved in the production of toxic gasses and consist of hazardous explosive steps that severely hurt and threaten ecological balance and human health. Therefore, in this study, we investigated the green, effective, and economical approach for the synthesis of graphene by using Vernonia amygdalina (VA) plant leaf extracts for the effective and efficient reduction of GO. The nonexplosive two-step synthesis of GO in a short period of time in the absence of an ice bath was used in this study. The appropriate solvent for the extraction of VA for the green synthesis of graphene was methanol, and the reducing and capping agent in the plant extract was identified to be terpenoids and polyphenols. The graphene/rGO obtained this way was characterized by UV-VIS, XRD, FTIR, SEM, HR-TEM, and EDAX that confirmed the successful reduction of GO to graphene under the hydrothermal process. The HR-TEM images showed the development of few layers of graphene. The FTIR result also shows the complete reduction of GO. Hence, methanol extracted VA leaves consisted of the most appropriate compounds for reducing and capping agent in the green synthesis and could be the preferred method for the large-scale production of graphene-based materials.

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A Novel and Simplest Green Synthesis Method of Reduced Graphene Oxide Using Methanol Extracted Vernonia Amygdalina: Large-Scale Production

Abstract 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. Graphical Abstract

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Effects of Azadirachta Indica Leaf Extract, Capping Agents, on the Synthesis of Pure And Cu Doped ZnO-Nanoparticles: A Green Approach and Microbial Activity

Bedasa Abdisa Gonfa

Papers

Synthesis of Zinc Oxide Nanoparticles Using Leaf Extract of Lippia adoensis (Koseret) and Evaluation of Its Antibacterial Activity

Synthesis of Copper Oxide Nanoparticles Using Plant Leaf Extract of Catha edulis and Its Antibacterial Activity

Synthesis of Titanium Oxide Nanoparticles Using Root Extract of Kniphofia foliosa as a Template, Characterization, and Its Application on Drug Resistance Bacteria

A Novel and Simplest Green Synthesis Method of Reduced Graphene Oxide Using Methanol Extracted Vernonia Amygdalina: Large-Scale Production

Effects of Azadirachta Indica Leaf Extract, Capping Agents, on the Synthesis of Pure And Cu Doped ZnO-Nanoparticles: A Green Approach and Microbial Activity