Nanoarchitectonics of ZnO Nanoparticles Mediated by Extract of Tulbaghia violacea and Their Cytotoxicity Evaluation

Alkaline protease based hydrothermal synthesis of novel Pd/CuO/ZnO nanocomposite: A new entry into photocatalytic and biomedical applications

Here, we reported the process for the production of Pd/CuO/ZnO nanocomposite utilizing alkaline protease from Phalaris minor seed extract, which is a unique, effective biogenic approach. Alkaline protease performed a crucial part in the reduction, capping and stabilization of Pd/CuO/ZnO nanocomposites. A series of physicochemical techniques were used to inquire the formation, size, shape and crystalline nature of Pd/CuO/ZnO nanocomposites. The notable performance of the synthesized nanocomposite as a photocatalyst and an antibacterial disinfectant was astonishing. The Pd/CuO/ZnO nanocrystals showed considerable photocatalytic activity by eliminating 99 % of the methylene blue (MB) in <30 min of exposure. After three test cycles, the nanocatalyst demonstrated exceptional reliability as a photocatalyst. The nanocomposite was also discovered to be an effective antibacterial agent, with zones of inhibitory activity for Staphylococcus aureus and Escherichia coli bacteria of 30(±0.2), 27(±0.3), 22(±0.2), and 21(±0.3) mm, respectively, in both light and dark conditions. Moreover, the Pd/CuO/ZnO nanocomposites showed strong antioxidant activity by efficiently scavenging 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals. The photocatalytic, antibacterial and antioxidative performance of Pd, CuO, ZnO, and CuO/ZnO were also assessed for the sake of comparison. This work shows that biogenic nanocomposites may be employed as a feasible alternative photocatalyst for the decomposition of dyes in waste water as well as a sustainable antibacterial agent.

Waste remediation: Low-temperature synthesis of hybrid Cu(OH)2/CuO and CuO nanostructures from spent printed circuit boards and their dye degradation studies

The demand for environmentally friendly and sustainable resource utilization techniques for recycling waste printed circuit boards is significant due to their status as valuable secondary resources, containing high-purity copper and precious metals. In this context, Cu(OH)2/CuO and CuO nanostructures were fabricated using alkaline precipitation and low-temperature aging methods using the strip solution originated from laboratory-scale spent mobile phone printed circuit board recovery process. XRD, FTIR, FESEM-EDX, and TEM were utilized to characterize the as-recovered nanoproducts. A hybrid structure of Cu(OH)2/CuO was formed at 70°, and monoclinic CuO phase was formed at 80 °C aging time. The results show that Cu(OH)2/CuO nanoflakes have an average crystallite size of 24.06 nm and a particle width of 22 ± 3 nm. Cu(OH)2/CuO nanoflakes formed at 70 °C aging temperature and 24-h residence time have finer crystallite and particle sizes than CuO-ridged nanospheres formed at 80 °C aging temperature. The optical band gap energy of Cu(OH)2/CuO and CuO nanostructures formed was found to be 2.28 eV and 2.22 eV, respectively. The hybrid Cu(OH)2/CuO nanostructure photocatalyzed the decomposed 97.28% rhodamine blue using a visible light source, whereas the CuO nanostructure degraded only 14.64% rhodamine blue dye under similar conditions. A surfactant-less hybrid structure is developed without the use of any chemical precursor. Thus, a high value-added product is produced using one waste material to remove another waste in wastewater treatment.

A Review of the Green Synthesis of ZnO Nanoparticles Utilising Southern African Indigenous Medicinal Plants

Metal oxide nanoparticles (NPs), such as zinc oxide (ZnO), have been researched extensively for applications in biotechnology, photovoltaics, photocatalysis, sensors, cosmetics, and pharmaceuticals due to their unique properties at the nanoscale. ZnO NPs have been fabricated using conventional physical and chemical processes, but these techniques are limited due to the use of hazardous chemicals that are bad for the environment and high energy consumption. Plant-mediated synthesis of ZnO NPs has piqued the interest of researchers owing to secondary metabolites found in plants that can reduce Zn precursors and stabilise ZnO NPs. Thus, plant-mediated synthesis of ZnO NPs has become one of the alternative green synthesis routes for the fabrication of ZnO NPs. This is attributable to its environmental friendliness, simplicity, and the potential for industrial-scale expansion. Southern Africa is home to a large and diverse indigenous medicinal plant population. However, the use of these indigenous medicinal plants for the preparation of ZnO NPs is understudied. This review looks at the indigenous medicinal plants of southern Africa that have been used to synthesise ZnO NPs for a variety of applications. In conclusion, there is a need for more exploration of southern African indigenous plants for green synthesis of ZnO NPs.

Biogenic Synthesis of ZnO Nanoparticles and Their Application as Bioactive Agents: A Critical Overview

Zinc oxide is a safe material for humans, with high biocompatibility and negligible cytotoxicity. Interestingly, it shows exceptional antimicrobial activity against bacteria, viruses, fungi, etc., especially when reduced to the nanometer size. As it is easily understandable, thanks to its properties, it is at the forefront of safe antimicrobials in this pandemic era. Besides, in the view of the 2022 European Green Deal announced by the European Commission, even science and nanotechnology are moving towards “greener” approaches to the synthesis of nanoparticles. Among them, biogenic ZnO nanoparticles have been extensively studied for their biological applications and environmental remediation. Plants, algae, fungi, yeast, etc., (which are composed of naturally occurring biomolecules) play, in biogenic processes, an active role in the formation of nanoparticles with distinct shapes and sizes. The present review targets the biogenic synthesis of ZnO nanoparticles, with a specific focus on their bioactive properties and antimicrobial application.

Microbial Mediated Synthesis of Zinc Oxide Nanoparticles, Characterization and Multifaceted Applications

Nanoparticles have gained considerable importance compared to bulk counterparts due to their unique properties. Due to their high surface to volume ratio and high reactivity, metallic and metal-oxide nanostructures have shown great potential applications. Among them, zinc oxide nanoparticles (ZnONPs) have gained tremendous attention attributed to their unique properties such as low toxicity, biocompatibility, simplicity, easy fabrication, and environmental friendly. Remarkably, ZnONPs exhibit optical, physical, antimicrobial, anticancer, anti-inflammatory and wound healing properties. These nanoparticles have been applied in various fields such as in biomedicine, biosensors, electronics, food, cosmetic industries, textile, agriculture and environment. The synthesis of ZnONPs can be performed by chemical, physical and biological methods. Although the chemical and physical methods suffer from some disadvantages such as the involvement of high temperature and pressure conditions, high cost and not environmentally friendly, the green synthesis of ZnONPs offers a promising substitute to these conventional methods. On that account, the microbial mediated synthesis of ZnONPs is clean, eco-friendly, nontoxic and biocompatible method. This paper reviews the microbial synthesis of ZnONPs, parameters used for the optimization process and their physicochemical properties. The potential applications of ZnONPs in biomedical, agricultural and environmental fields as well as their toxic aspects on human beings and animals have been reviewed.

Biogenic Synthesis of CuO, ZnO, and CuO-ZnO Nanoparticles Using Leaf Extracts of Dovyalis caffra and Their Biological Properties

Biogenic metal oxide nanoparticles (NPs) have emerged as a useful tool in biology due to their biocompatibility properties with most biological systems. In this study, we report the synthesis of copper oxide (CuO), zinc oxide (ZnO) nanoparticles (NPs), and their nanocomposite (CuO–ZnO) prepared using the phytochemical extracts from the leaves of Dovyalis caffra (kei apple). The physicochemical properties of these nanomaterials were established using some characterization techniques including X-ray diffraction analysis (XRD), ultraviolet-visible spectroscopy (UV-vis), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDX). The XRD result confirmed the presence of a monoclinic CuO (Tenorite), and a hexagonal ZnO (Zincite) nanoparticles phase, which were both confirmed in the CuO–ZnO composite. The electron microscopy of the CuO–ZnO, CuO, and ZnO NPs showed a mixture of nano-scale sizes and spherical/short-rod morphologies, with some agglomeration. In the constituent’s analysis (EDX), no unwanted peak was found, which showed the absence of impurities. Antioxidant properties of the nanoparticles was studied, which confirmed that CuO–ZnO nanocomposite exhibited better scavenging potential than the individual metal oxide nanoparticles (CuO, and ZnO), and ascorbic acid with respect to their minimum inhibitory concentration (IC₅₀) values. Similarly, the in vitro anticancer studies using MCF7 breast cancer cell lines indicated a concentration-dependent profile with the CuO–ZnO nanocomposite having the best activity over the respective metal oxides, but slightly lower than the standard 5-Fluorouracil drug.