Facile green fabrication of nanostructure ZnO plates, bullets, flower, prismatic tip, closed pine cone: Their antibacterial, antioxidant, photoluminescent and photocatalytic properties

Preparation of a polyaniline/ZnO-NPs composite for the visible-light-driven hydrogen generation

Compositions of ZnO nanoparticles and polyaniline, in the form of emeraldine salt, were manufactured as thin layers by using the spin-coating method. Then, the effect of polyaniline content on their photoelectrochemical characteristics was studied. Results indicate that all the samples are sensitive to light. Besides, with 0.30% of PANI, the composite sample demonstrates the highest photocurrent density; also, its photocurrent increment starts to increase at a voltage of ⁓ 1.23 V (vs. RHE), which is approximately in accordance with the theoretical potential of water electrolysis. Furthermore, since the rate of electron-hole recombination in this composite sample is the lowest, it possesses the highest photoelectrochemical efficiency. Main findings were analyzed with respect to UV-visible absorption and photoluminescence spectra as well as SEM micrographs of the samples and Raman spectral measurements. Besides, electrochemical impedance spectroscopy analysis was applied to both pure ZnO and the sample with the best response. Effects of drying temperature and layer thickness were also investigated.

A novel green preparation of zinc oxide nanoparticles with Hibiscus sabdariffa L.: photocatalytic performance, evaluation of antioxidant and antibacterial activity

This study investigates the eco-friendly synthesis of zinc oxide nanoparticles (ZnO NPs) utilizing an aqueous solution of Hibiscus sabdariffa L. flower extract, which is acts as reducing agent as well as capping agent. The Fourier transform infrared spectroscopy (FTIR) results revealed the presence of flavonoids and phenols in the plant extract, indicating that they were the major agents capable of reducing zinc nitrate salt. According to our x-ray diffraction (XRD) results, ZnO-NPs exhibit a particular phase wurtzite structure. The ZnO-NPs are spherical in shape and have an average size of 15 nm, according to the measurements of electron microscope (SEM) and transmission electron microscope (TEM) measurements. Energy dispersion (EDX) analysis demonstrates that the NPs are mainly composed of zinc and oxygen. The zeta potential of these nanoparticles shows that they are very stable. The antibacterial activity of ZnO-NPs was tested using agar dilutions with a variety of gram-positive and gram-negative microorganisms. According to the research results, ZnO-NPs can be established as an extremely specific antibacterial agent for a wide variety of organisms to prevent bacterial growth. Furthermore, the antioxidant properties of ZnO-NPs were determined using the 2,2 diphenyl-1-picrylhydrazyl hydrate (DPPH) radical scavenging approach, and the IC50 value of 38 μg/mL was measured for ZnO-NPs. Furthermore, the biosynthesized ZnO-NPs showed significant catalytic performance of methyl orange (MO) under UV irradiation. Overall, ZnO-NPs in their produced state have excellent potential in biomedical and wastewater treatment applications. Radical scavengers were used to evaluate the role of radicals in the reaction mechanism.

Biogenic Zinc oxide nanoparticles from Celosia argentea: toward improved antioxidant, antibacterial, and anticancer activities

Biogenic Zinc oxide (ZnO) nanoparticles (NPs) were synthesized from Celosia argentea (C. argentea) plant extract. Structural analysis confirms the successful synthesis of biogenic zinc oxide NPs from C. argentea extract. The biogenic ZnO NPs have an average particle size of 21.55 ± 4.73 nm, a semispherical shape, and a specific surface area of about 50 m2/g. The biogenic ZnO NPs have a powerful radical scavenging activity (Ic50 = 91.24 mg/ml) comparable to ascorbic acid (ASC) as a standard (Ic50 = 14.37 mg/ml). The antibacterial efficacy was tested against gram-positive and gram-negative bacteria using an agar disc diffusion method. Gram-positive strains with biogenic ZnO NPs have a greater bactericidal impact than gram-negative strains in a concentration-dependent manner. Anticancer activity against Liver hepatocellular cells (HepG2) and Human umbilical vein endothelial cells (HUVEC) was evaluated using a [3-(4,5-dimethylthiazol-2-yl)-2,5diphenyl tetrazolium bromide] (MTT) assay. The results reflect the concentration-dependent cytotoxic effect of biogenic ZnO NPs against HepG2 cells even at low concentrations (Ic50 = 49.45 μg/ml) compared with doxorubicin (Ic50 = 14.67 μg/ml) and C. argentea extract (Ic50 = 112.24 μg/ml). The cell cycle and gene expression were analyzed to determine the potential anticancer mechanism. The flow cytometric analysis of the cell cycle revealed that biogenic ZnO NPs induce oxidative stress that activates the apoptotic genes NF-κB, CY-C, and P53, leading to cell death. The Celosia argentea improved the antioxidant, antibacterial, and anticancer activities of ZnO NPs without altering their structural properties. The effect of green synthesis on the bioactivity of biogenic ZnO NPs in vivo is recommended for future work.

Bioactive ZnO Nanoparticles: Biosynthesis, Characterization and Potential Antimicrobial Applications

In recent years, biosynthesized zinc oxide nanoparticles (ZnONPs) have gained tremendous attention because of their safe and non-toxic nature and distinctive biomedical applications. A diverse range of microbes (bacteria, fungi and yeast) and various parts (leaf, root, fruit, flower, peel, stem, etc.) of plants have been exploited for the facile, rapid, cost-effective and non-toxic synthesis of ZnONPs. Plant extracts, microbial biomass or culture supernatant contain various biomolecules including enzymes, amino acids, proteins, vitamins, alkaloids, flavonoids, etc., which serve as reducing, capping and stabilizing agents during the biosynthesis of ZnONPs. The biosynthesized ZnONPs are generally characterized using UV-VIS spectroscopy, TEM, SEM, EDX, XRD, FTIR, etc. Antibiotic resistance is a serious problem for global public health. Due to mutation, shifting environmental circumstances and excessive drug use, the number of multidrug-resistant pathogenic microbes is continuously rising. To solve this issue, novel, safe and effective antimicrobial agents are needed urgently. Biosynthesized ZnONPs could be novel and effective antimicrobial agents because of their safe and non-toxic nature and powerful antimicrobial characteristics. It is proven that biosynthesized ZnONPs have strong antimicrobial activity against various pathogenic microorganisms including multidrug-resistant bacteria. The possible antimicrobial mechanisms of ZnONPs are the generation of reactive oxygen species, physical interactions, disruption of the cell walls and cell membranes, damage to DNA, enzyme inactivation, protein denaturation, ribosomal destabilization and mitochondrial dysfunction. In this review, the biosynthesis of ZnONPs using microbes and plants and their characterization have been reviewed comprehensively. Also, the antimicrobial applications and mechanisms of biosynthesized ZnONPs against various pathogenic microorganisms have been highlighted.

Cell free extract-mediated biogenic synthesis of ZnONPs and their application with kanamycin as a bactericidal combination

Antimicrobial resistance (AMR) is a main public health issue and a challenge for the scientific community all over the globe. Hence, there is a burning need to build new bactericides that resist the AMR. The ZnONPs were produced by cell free extract of mint (Mentha piperita L.) leaves. Antibiotics that are ineffective against resistant bacteria like Escherichia coli and Staphylococcus aureus were treated. The antibiotics were first screened, and then antibacterial activity was checked by disk diffusion, and MIC of Mp-ZnONPs individually and using Kanamycin (KAN) were determined against these pathogens by broth microdilution method. The synergism between Mp-ZnONPs and KAN was confirmed by checkerboard assay. The MIC showed robust antibacterial activity against the tested pathogens. The combination of KAN and Mp-ZnONPs reduces the MIC of KAN as it efficiently inhibits E. coli's growth, and KAN significantly enhances the antibacterial activity of Mp-ZnONPs. Taken together, Mp-ZnONPs have strong antimicrobial activity, and KAN significantly improves it against the tested pathogens, which would offer an effective, novel, and benign therapeutic methodology to regulate the incidence. The combination of Mp-ZnONPs and KAN would lead to the development of novel bactericides, that could be used in the formulation of pharmaceutical products.

Biosynthesis approach of zinc oxide nanoparticles for aqueous phosphorous removal: physicochemical properties and antibacterial activities

In this study, phosphorus (PO43--P) is removed from water samples using zinc oxide nanoparticles (ZnO NPs). These nanoparticles are produced easily, quickly, and sustainably using Onion extracts (Allium cepa) at an average crystallite size of 8.13 nm using the Debye-Scherrer equation in the hexagonal wurtzite phase. The characterization and investigation of bio-synthesis ZnO NPs were carried out. With an initial concentration of 250 mg/L of P, the effects of the adsorbent dose, pH, contact time, and temperature were examined. At pH = 3 and T = 300 K, ZnO NPs achieved the optimum sorption capacity of 84 mg/g, which was superior to many other adsorbents. The isothermal study was found to fit the Langmuir model at a monolayer capacity of 89.8 mg/g, and the kinetic study was found to follow the pseudo-second-order model. The adsorption process was verified to be endothermic and spontaneous by thermodynamic characteristics. As a result of their low cost as an adsorbent and their high metal absorption, ZnO NPs were found to be the most promising sorbent in this investigation and have the potential to be used as effective sorbents for the removal of P from aqueous solutions. The antimicrobial activity results showed that ZnO NPs concentration had greater antibacterial activity than conventional Cefotaxime, which was utilized as a positive control in the inhibitory zone. However, no inhibitory zone was visible in the controlled wells that had been supplemented with onion extract and DMSO.

Multifactorial role of nanoparticles in alleviating environmental stresses for sustainable crop production and protection

In the era of dire environmental fluctuations, plants undergo several stressors during their life span, which severely impact their development and overall growth in negative aspects. Abiotic stress factors, especially moisture stress i.e shortage (drought) or excess (flooding), salinity, temperature divergence (i.e. heat and cold stress), heavy metal toxicity, etc. create osmotic and ionic imbalance inside the plant cells, which ultimately lead to devastating crop yield, sometimes crop failure. Apart from the array of abiotic stresses, various biotic stress caused by pathogens, insects, and nematodes also affect production. Therefore, to combat these major challenges in order to increase production, several novel strategies have been adapted, among which the use of nanoparticles (NPs) i.e. nanotechnology is becoming an emerging tool in various facets of the current agriculture system, nowadays. This present review will elaborately depict the deployment and mechanisms of different NPs to withstand these biotic and abiotic stresses, along with a brief overview and indication of the future research works to be oriented based on the steps provided for future research in advance NPs application through the sustainable way.

Biological Activities of Sargassum Algae Mediated ZnO and Co Doped ZnO Nanoparticles as Enhanced Antioxidant and Anti-Diabetic Agents

Brown macroalgae (BMG) were used as carriers for ZnO (ZnO/BMG) and cobalt-doped ZnO (Co-ZnO/BMG) via facile microwave-assisted hydrothermal synthesis. The multifunctional structures of synthesized composites were evaluated as enhanced antioxidant and anti-diabetic agents based on the synergistic effects of ZnO, Co-ZnO, and BMG. BMG substrate incorporation and cobalt doping notably enhanced the bioactivity of the synthesized ZnO nanoparticles. As an antioxidant, the Co-ZnO/BMG composite exhibited highly effective scavenging properties for the common free reactive oxygen radicals (DPPH [89.6 ± 1.5%], nitric oxide [90.2 ± 1.3%], ABTS [87.7 ± 1.8%], and O2●- [46.7 ± 1.9%]) as compared to ascorbic acid. Additionally, its anti-diabetic activity was enhanced significantly and strongly inhibited essential oxidative enzymes (porcine α-amylase (90.6 ± 1.5%), crude α-amylase (84.3 ± 1.8%), pancreatic α-glucosidase (95.7 ± 1.4%), crude intestinal α-glucosidase (93.4 ± 1.8%), and amyloglucosidase (96.2 ± 1.4%)). Co-ZnO/BMG inhibitory activity was higher than that of miglitol, and in some cases, higher than or close to that of acarbose. Therefore, the synthetic Co-ZnO/BMG composite can be used as a commercial anti-diabetic and antioxidant agent, considering the cost and adverse side effects of current drugs. The results also demonstrate the impact of cobalt doping and BMG integration on the biological activity of ZnO.

Synthesis and Characterization of Green Zinc-Metal-Pillared Bentonite Mediated Curcumin Extract (Zn@CN/BE) as an Enhanced Antioxidant and Anti-Diabetes Agent

Green zinc-metal-pillared bentonite mediated curcumin extract (Zn@CN/BE) was synthesized and characterized as a low-cost and multifunctional (curcumin-based phytochemicals, zinc-capped curcumin, zinc/curcumin complexes, and zinc-pillared bentonite) antioxidant and antidiabetic agent with enhanced activity. The activities of the Zn@CN/BE structure were assessed in comparison with curcumin and ZnO as individual components and in the presence of miglitol and acarbose commercial drugs as controls. The structure validated remarkable antioxidant activities against the common oxidizing radicals (nitric oxide (94.7 ± 1.83%), DPPH (96.4 ± 1.63%), ABTS (92.8 ± 1.33%), and superoxide (62.3 ± 1.63 %)) and inhibition activities against the main oxidizing enzymes (porcine α-amylase (89.3 ± 1.13%), murine α-amylase (70.8 ± 1.54%), pancreatic α-Glucosidase (99.3 ± 1.23%), intestinal α-Glucosidase (97.7 ± 1.24%), and amyloglucosidase (98.4 ± 1.64%)). The reported activities are higher than the activities of individual components and the studied ascorbic acid as well as the commercial drugs. This enhancement effect was assigned to the impact of the zinc pillaring process within the curcumin/bentonite host, which induced the stability, dispersions, and interactive interface of the essential active compounds in addition to the solubility and release rate of the intercalated curcumin extract. This paper recommends the application of the Zn@CN/BE structure as an enhanced, low-cost, biocompatible, safe, and simply produced antioxidant and antidiabetic agent.

Adsorptive removal of pharmaceutically active compounds from multicomponent system using Azadirachta indica induced zinc oxide nanoparticles: analysis of competitive and cooperative adsorption

In this research, zinc oxide (ZnO) nanoparticles synthesized using neem leaf (Azadirachta indica) extract were used as an adsorbent for removing two widely used pharmaceutical compounds acetaminophen (AMP) and sulfadiazine (SDZ). The synthesized ZnO nanoparticles were characterized using SEM-EDS, FTIR, TEM, BET, and XRD analysis. The synthesized ZnO nanoparticles were found to be in the size range of 10 nm with a surface area of 48.551 m²/g. The adsorptive performance of ZnO nanoparticles in both mono-component (MoS) and multi-component system (MuS) was investigated under various operational parameters viz. contact time, temperature, pH, concentration of pharmaceutical compound and ZnO nanoparticles dose. It was observed that the maximum adsorption capacity of ZnO nanoparticles was 7.87 mg/g and 7.77 mg/g for AMP and SDZ, respectively, under the optimum conditions of 7 pH and 2 g/L adsorbent dosage. The experimental data best-fitted with the pseudo-second-order model and Langmuir model, indicating monolayer chemisorption. Further investigation on removal of AMP and SDZ from multicomponent system was modelled using a Langmuir competitive model. The desorption study has shown 25.28% and 22.4% removal of AMP and SDZ from the surface of ZnO nanoparticles. In general, green synthesized ZnO nanoparticles can be utilized effectively as adsorbent for removal of pharmaceutically active compounds from wastewater.

Microwave-Induced CuO Nanorods: A Comparative Approach between Curcumin, Quercetin, and Rutin to Study Their Antioxidant, Antimicrobial, and Anticancer Effects against Normal Skin Cells and Human Breast Cancer Cell Lines MCF-7 and T-47D

Herein, we explore the biological properties of curcumin, quercetin, and rutin by loading them onto porous CuO nanorods (NRs). The CuO NRs were synthesized using the microwave irradiation method through a chemical reaction between CuSO₄·5H₂O and NaOH in the presence of the anionic stabilizer sodium dodecyl sulfate. The shape and surface morphology of CuO NRs were examined with two microscopic techniques: high-resolution transmission electron microscopy (HR-TEM) and field emission scanning electron microscopy (FESEM). Their average diameter was measured by TEM to be 15 ± 2 nm. The porosity and interfacial area of the fabricated material were determined by Brunauer-Emmett-Teller analysis. After successful synthesis, CuO NRs were loaded with polyphenolic curcumin, quercetin, and rutin, with the loading efficiency of 57.8, 62.2, and 81.2%, respectively, which was confirmed by UV-visible and infra-red spectroscopy and finally with a thermal gravimetric technique. Their radical scavenging activity was measured with the 2,2-diphenyl-1-picrylhydrazyl radical and compared with the control (ascorbic acid). Further, good bactericidal effects were observed against both Gram-positive bacterial strains, including Staphylococcus aureus and Bacillus subtilis, and Gram-negative bacterial strains, including Salmonella typhi, Pseudomonas aeruginosa, Escherichia coli, and Klebsiella pneumoniae. Excellent anticancer activity was observed against normal skin cells and breast cancer cells T-47D and MCF-7.

Green synthesis of zinc oxide nanoparticles using Cocos nucifera leaf extract: characterization, antimicrobial, antioxidant and photocatalytic activity

Zinc oxide nanoparticles (ZnO NPs) have been successfully prepared using Cocos nucifera leaf extract and their antimicrobial, antioxidant and photocatalytic activity investigated. The structural, compositional and morphological properties of the NPs were recorded and studied systematically to confirm the synthesis. The aqueous suspension of NPs showed an ultraviolet-visible (UV-Vis) absorption maxima of 370 nm, indicating primarily its formation. X-ray diffraction analysis identified the NPs with a hexagonal wurtzite structure and an average particle size of 16.6 nm. Fourier transform infrared analysis identified some biomolecules and functional groups in the leaf extract as responsible for the encapsulation and stabilization of ZnO NPs. Energy-dispersive X-ray analysis showed the desired elemental compositions in the material. A flower-shaped morphology of ZnO NPs was observed by scanning electron microscopy, with a grain size of around 15 nm. The optical properties of the NPs were studied by UV-Vis spectroscopy, and the band gap was calculated as 3.37 eV. The prepared ZnO NPs have demonstrated antimicrobial activity against T. harzianum and S. aureus, with a zone of inhibition of 14 and 10 mm, respectively. The photocatalytic behaviour of ZnO NPs showed absorbance degradation at around 640 nm and it discoloured methylene blue dye after 1 h, with a degradation maximum of 84.29%. Thus, the prepared ZnO NPs could potentially be used in antibiotic development and pharmaceutical industries, and as photocatalysts.

One-pot green synthesis of ZnO nanoparticles using Scoparia Dulcis plant extract for antimicrobial and antioxidant activities

Nanostructured Zinc oxide (ZnO) materials have attained exciting research interests among various metal oxide nanoparticles due to their unique features. Thus, the scope of applications for ZnO nanoparticles (ZnO NPs) is vast and efficient. The current study demonstrates a simple and environmental-friendly approach for the synthesis of ZnO NPs using the extract of the Scoparia Dulcis. Scoparia Dulcis is a common medicinal plant in Kerala (India) that is traditionally used for its medicinal properties. Morphological characterizations of the as-synthesized ZnO NPs were evaluated using X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), and field-emission scanning electron microscopy (FESEM). The results revealed that ZnO NPs showed pebble-like morphology and possessed an average particle size of ~ 20 nm. Further, antibacterial and antifungal activities of as-prepared ZnO NPs were investigated against E. coli, Staphylococcus aureus, as well as Candida albicans, and Aspergillus niger, respectively, using the agar-well diffusion method. The results revealed that the prepared ZnO NPs shows excellent antimicrobial activity against the examined microorganisms. Moreover, the antioxidant activity of the as-synthesized ZnO NPs was evaluated using the DPPH assay, which indicated an excellent IC50 value of 1.78 μg/mL that shows high antioxidant activity. All these results proved that the S. dulcis plant extract-mediated synthesis method is a simple, low-cost, eco-friendly procedure for preparing efficient ZnO NPs for biomedical applications.

Current Research on Zinc Oxide Nanoparticles: Synthesis, Characterization, and Biomedical Applications

Zinc oxide nanoparticles (ZnO-NPs) have piqued the curiosity of researchers all over the world due to their extensive biological activity. They are less toxic and biodegradable with the capacity to greatly boost pharmacophore bioactivity. ZnO-NPs are the most extensively used metal oxide nanoparticles in electronic and optoelectronics because of their distinctive optical and chemical properties which can be readily modified by altering the morphology and the wide bandgap. The biosynthesis of nanoparticles using extracts of therapeutic plants, fungi, bacteria, algae, etc., improves their stability and biocompatibility in many biological settings, and its biofabrication alters its physiochemical behavior, contributing to biological potency. As such, ZnO-NPs can be used as an effective nanocarrier for conventional drugs due to their cost-effectiveness and benefits of being biodegradable and biocompatible. This article covers a comprehensive review of different synthesis approaches of ZnO-NPs including physical, chemical, biochemical, and green synthesis techniques, and also emphasizes their biopotency through antibacterial, antifungal, anticancer, anti-inflammatory, antidiabetic, antioxidant, antiviral, wound healing, and cardioprotective activity. Green synthesis from plants, bacteria, and fungus is given special attention, with a particular emphasis on extraction techniques, precursors used for the synthesis and reaction conditions, characterization techniques, and surface morphology of the particles.

Overview on Recent Developments in the Design, Application, and Impacts of Nanofertilizers in Agriculture

Nutrient management is always a great concern for better crop production. The optimized use of nutrients plays a key role in sustainable crop production, which is a major global challenge as it depends mainly on synthetic fertilizers. A novel fertilizer approach is required that can boost agricultural system production while being more ecologically friendly than synthetic fertilizers. As nanotechnology has left no field untouched, including agriculture, by its scientific innovations. The use of nanofertilizers in agriculture is in the early stage of development, but they appear to have significant potential in different ways, such as increased nutrient-use efficiency, the slow release of nutrients to prevent nutrient loss, targeted delivery, improved abiotic stress tolerance, etc. This review summarizes the current knowledge on various developments in the design and formulation of nanoparticles used as nanofertilizers, their types, their mode of application, and their potential impacts on agricultural crops. The main emphasis is given on the potential benefits of nanofertilizers, and we highlight the current limitations and future challenges related to the wide-scale application before field applications. In particular, the unprecedent release of these nanomaterials into the environment may jeopardize human health and the ecosystem. As the green revolution has occurred, the production of food grains has increased at the cost of the disproportionate use of synthetic fertilizers and pesticides, which have severely damaged our ecosystem. We need to make sure that the use of these nanofertilizers reduces environmental damage, rather than increasing it. Therefore, future studies should also check the environmental risks associated with these nanofertilizers, if there are any; moreover, it should focus on green manufactured and biosynthesized nanofertilizers, as well as their safety, bioavailability, and toxicity issues, to safeguard their application for sustainable agriculture environments.

Efficient Removal of Methylene Blue and Ciprofloxacin from Aqueous Solution Using Flower-like, Nanostructured ZnO Coating under UV Irradiation

Flower-like ZnO architectures assembled with many nanorods were successfully synthesized through Thermionic Vacuum Arc, operated both in direct current (DC-TVA) and a pulsed mode (PTVA), and coupled with annealing in an oxygen atmosphere. The prepared coatings were analysed by scanning-electron microscopy with energy-dispersive X-ray-spectroscopy (SEM-EDX), X-ray-diffraction (XRD), and photoluminescence (PL) measurements. By simply modifying the TVA operation mode, the morphology and uniformity of ZnO nanorods can be tuned. The photocatalytic performance of synthesized nanostructured ZnO coatings was measured by the degradation of methylene-blue (MB) dye and ciprofloxacin (Cipro) antibiotic. The ZnO (PTVA) showed enhancing results regarding the photodegradation of target contaminants. About 96% of MB molecules were removed within 60 min of UV irradiation, with a rate constant of 0.058 min−1, which is almost nine times higher than the value of ZnO (DC-TVA). As well, ZnO (PTVA) presented superior photocatalytic activity towards the decomposition of Cipro, after 240 min of irradiation, yielding 96% degradation efficiency. Moreover, the agar-well diffusion assay performance against both Gram-positive and Gram-negative bacteria confirms the degradation of antibiotic molecules by the UV/ZnO (PTVA) approach, without the formation of secondary hazardous products during the photocatalysis process. Repeated cyclic usage of coatings revealed excellent reusability and operational stability.

Synthesis, characterization, and photocatalytic activity of ZnO nanoparticles using water extract of waste coconut husk

The present work reports the use of natural alkaline extract from coconut husk ash as a precipitating agent for metal oxide nanoparticles synthesis. The abundance of K₂O and K₂CO₃ in it makes the extract highly basic and could be the alternative source of basic media in the laboratory. In this study, highly photoactive zinc oxide nanoparticles have been synthesized using water extract of waste coconut husk ash in a green approach which is considered as replacement of homogeneous base like NaOH and KOH. The formation of zinc oxide nanoparticles at different pH of the solution of coconut husk ash was confirmed through powder XRD, BET, SEM-EDX, UV-Vis, FTIR, and photoluminescence spectroscopy. The photocatalytic performance of the samples was evaluated through the degradation of methylene blue (MB) and methyl orange (MO) under solar irradiation which undergo degradation around 97% and 68% within 120 min, respectively. The high photocatalytic activity and rate constant could be attributed to the large surface area due to small particle size that could provide quicker photon absorption and reduction of charge carrier recombination. This current work introduces a new method to reduce energy consumption for the synthesis of highly photoactive low-cost zinc oxide nanoparticles.

Biosynthesis of ZnO Nanoparticles Using Capsicum chinense Fruit Extract and Their In Vitro Cytotoxicity and Antioxidant Assay

Green synthesis of nanoparticles (NPs) has garnered wide research interest due to inherent properties such as eco-friendliness, compatibility with substrates, and cost-effectiveness. Here, zinc oxide nanoparticles (ZnO-NPs) were successfully synthesized for the first time using Capsicum chinense fruit extract. The optical property of the green and conventionally synthesized ZnO-NPs was characterized by UV-vis spectrophotometer, which exhibited absorption peaks at 302 and 481 nm, respectively, and the morphology of the NPs was analyzed by transmission and scanning electron microscopies (TEM and SEM). The X-ray diffraction (XRD) studies showed that the hexagonal wurtzite phase was obtained, with high crystalline nature, while the electron dispersion X-ray study (EDX) revealed the purity of ZnO-NPs. The cytotoxicity assay of the biosynthesized and conventionally synthesized ZnO-NPs was evaluated using human embryonic kidney (HEK 293) and cervical carcinoma (HeLa) cell lines treated with various concentrations of the ZnO-NPs and they exhibited reasonable activity. Antioxidant activity of the ZnO-NPs was measured using 1, 1-diphenyl-2-picrylhydrazyl (DPPH) assay and the green ZnO-NPs exhibited higher activity compared to conventional ZnO-NPs. These findings proved that aqueous extracts of C. chinense fruit are effective for the biosynthesis of ZnO-NPs with anticancer and antioxidant potential.

Exploring the Journey of Zinc Oxide Nanoparticles (ZnO-NPs) toward Biomedical Applications

The field of nanotechnology is concerned with the creation and application of materials having a nanoscale spatial dimensioning. Having a considerable surface area to volume ratio, nanoparticles have particularly unique properties. Several chemical and physical strategies have been used to prepare zinc oxide nanoparticles (ZnO-NPs). Still, biological methods using green or natural routes in various underlying substances (e.g., plant extracts, enzymes, and microorganisms) can be more environmentally friendly and cost-effective than chemical and/or physical methods in the long run. ZnO-NPs are now being studied as antibacterial agents in nanoscale and microscale formulations. The purpose of this study is to analyze the prevalent traditional method of generating ZnO-NPs, as well as its harmful side effects, and how it might be addressed utilizing an eco-friendly green approach. The study’s primary focus is on the potential biomedical applications of green synthesized ZnO-NPs. Biocompatibility and biomedical qualities have been improved in green-synthesized ZnO-NPs over their traditionally produced counterparts, making them excellent antibacterial and cancer-fighting drugs. Additionally, these ZnO-NPs are beneficial when combined with the healing processes of wounds and biosensing components to trace small portions of biomarkers linked with various disorders. It has also been discovered that ZnO-NPs can distribute and sense drugs. Green-synthesized ZnO-NPs are compared to traditionally synthesized ones in this review, which shows that they have outstanding potential as a potent biological agent, as well as related hazardous properties.

Green synthesis of hybrid papain/Ni3(PO4)2 rods electrocatalyst for enhanced oxygen evolution reaction

An eco-friendly approach was used to produce the binary papain/Ni3(PO4)2 in the presence of papain, which is derived from green papaya fruits. Rod shape Papain/Ni3(PO4)2 showed excellent OER activities in alkaline, neutral and acidic media.

Synthesis and Characterization of Zinc Oxide Nanoparticles Using Acacia caesia Bark Extract and Its Photocatalytic and Antimicrobial Activities

This paper presents the green synthesis and characterization of ZnO nanoparticles and their microbial and photocatalytic application. The green synthesis of ZnO nanoparticles was carried out using Zinc nitrate hexahydrate and the bark extract of Acacia caesia (L.) Willd. The nanoparticles were synthesized at an optimum temperature of 65 °C followed by calcination at 400 °C. The samples were characterized using UV-visible spectroscopy, SEM, XRD, FTIR and EDX analysis. UV-visible spectroscopy showed a characteristic peak at 338 nm and the bandgap energy was found to be 3 eV which is specific for ZnO. SEM confirmed the presence of ZnO on its nanoscale. EDX gave the elemental details of Zinc constituting to 37.77% and Oxygen comprising 20.77% of its atomic weight. XRD analysis gave the diffractogram indexed at various angles corresponding to ZnO nanoparticles. It also revealed the average crystalline size to be 32.32 nm and the shape was found to be hexagonal. The functional group present in the nanoparticles was characterized using FTIR, which gave a characteristic peak at 485 cm−1. The synthesized nanoparticles exhibited significant photocatalytic (methyl blue under UV irradiation). The presence of nanoparticles induces changes in its kinetics, whose rate constants and correlation coefficients were analyzed during the photocatalytic degradation of the model pollutant Methyl Blue. Studies on antibacterial (Escherichia coli, Staphylococcus aureus), antifungal (Aspergillus niger, Candida albicans) and anti-inflammatory (COX assay) properties were also carried out. The nanoparticles were synthesized in an eco-friendly and cost-effective method. The study opens new horizons in the field of water treatment, biosensors and nanotechnology.

Plant-Mediated Zinc Oxide Nanoparticles: Advances in the New Millennium towards Understanding Their Therapeutic Role in Biomedical Applications

Zinc oxide nanoparticles have become one of the most popular metal oxide nanoparticles and recently emerged as a promising potential candidate in the fields of optical, electrical, food packaging, and biomedical applications due to their biocompatibility, low toxicity, and low cost. They have a role in cell apoptosis, as they trigger excessive reactive oxygen species (ROS) formation and release zinc ions (Zn2+) that induce cell death. The zinc oxide nanoparticles synthesized using the plant extracts appear to be simple, safer, sustainable, and more environmentally friendly compared to the physical and chemical routes. These biosynthesized nanoparticles possess strong biological activities and are in use for various biological applications in several industries. Initially, the present review discusses the synthesis and recent advances of zinc oxide nanoparticles from plant sources (such as leaves, stems, bark, roots, rhizomes, fruits, flowers, and seeds) and their biomedical applications (such as antimicrobial, antioxidant, antidiabetic, anticancer, anti-inflammatory, photocatalytic, wound healing, and drug delivery), followed by their mechanisms of action involved in detail. This review also covers the drug delivery application of plant-mediated zinc oxide nanoparticles, focusing on the drug-loading mechanism, stimuli-responsive controlled release, and therapeutic effect. Finally, the future direction of these synthesized zinc oxide nanoparticles' research and applications are discussed.

Facile In Situ Synthesis of ZnO Flower-like Hierarchical Nanostructures by the Microwave Irradiation Method for Multifunctional Textile Coatings

ZnO nanoparticle-based multifunctional coatings were prepared by a simple, time-saving microwave method. Arginine and ammonia were used as precipitation agents, and zinc acetate dehydrate was used as a zinc precursor. Under the optimized conditions, flower-like morphologies of ZnO aggregates were obtained. The prepared nanopowders were characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and UV/Visible spectroscopy. The developed in situ synthesis with microwave irradiation enabled significant ZnO nanoparticle deposition on cotton fabrics, without additional steps. The functionalized textiles were tested as a photocatalyst in methylene blue (MB) photodegradation and showed good self-cleaning and UV-blocking properties. The coated cotton fabrics exhibited good antibacterial properties against common microbial trains (Staphylococcus aureus, Escherichia coli, and Candida albicans), together with self-cleaning and photocatalytic efficiency in organic dye degradation. The proposed microwave-assisted in situ synthesis of ZnO nanocoatings on textiles shows high potential as a rapid, efficient, environmentally friendly, and scalable method to fabricate functional fabrics.

Green Synthesis and Applications of ZnO and TiO2 Nanostructures

Over the last two decades, oxide nanostructures have been continuously evaluated and used in many technological applications. The advancement of the controlled synthesis approach to design desired morphology is a fundamental key to the discipline of material science and nanotechnology. These nanostructures can be prepared via different physical and chemical methods; however, a green and ecofriendly synthesis approach is a promising way to produce these nanostructures with desired properties with less risk of hazardous chemicals. In this regard, ZnO and TiO2 nanostructures are prominent candidates for various applications. Moreover, they are more efficient, non-toxic, and cost-effective. This review mainly focuses on the recent state-of-the-art advancements in the green synthesis approach for ZnO and TiO2 nanostructures and their applications. The first section summarizes the green synthesis approach to synthesize ZnO and TiO2 nanostructures via different routes such as solvothermal, hydrothermal, co-precipitation, and sol-gel using biological systems that are based on the principles of green chemistry. The second section demonstrates the application of ZnO and TiO2 nanostructures. The review also discusses the problems and future perspectives of green synthesis methods and the related issues posed and overlooked by the scientific community on the green approach to nanostructure oxides.

Synthesis of ZnO nanoparticles using peels of Passiflora foetida and study of its activity as an efficient catalyst for the degradation of hazardous organic dye

Creating a sustainable and effective approach to handling organic contaminants from industrial waste is an ongoing problem. In the present study, ZnO nanoparticles (ZnO NPs) were synthesized under a controlled ultrasound cavitation technique using the extract of Passiflora foetida fruit peels, which act as a reducing (i.e., reduction of metal salt) and stabilizing agent. The formation of monodispersed and hexagonal morphology (average size approximately 58 nm with BET surface area 30.83m2/g). The synthesized ZnO NPs were characterized by a various technique such as UV–visible spectroscopy, X-ray diffraction (XRD), Fourier-transform infrared (FTIR), Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Transmission electron microscopy (TEM), Thermogravimetric analysis (TGA) and Dynamic light scattering (DLS). Further, the XRD pattern confirmed the hexagonal wurtzite structure of synthesized ZnONPs. The ZnO NPs exhibit excellent degradation efficiency towards organic pollutant dyes, i.e., Methylene blue (MB) (93.25% removal) and Rhodamine B (91.06% removal) in 70 min, under natural sunlight with apparent rate constant 0.0337 min−1 (R2 = 0.9749) and 0.0347 min−1 (R2 = 0.9026) respectively.Zeta potential study shows the presence of a negative charge on the surface of ZnO NPs. The use of green synthesized ZnO NPs is a good choice for wastewater treatment, given their high reusability and photocatalytic efficiency, along with adaptability to green synthesis.

Single nozzle electrospinning promoted hierarchical shell wall structured zinc oxide hollow tubes for water remediation

HYPOTHESIS

Electrospun metal oxide hollow tubes are of great interest owing to their unique structural advantages compared to solid nanofibers. Although intensive research on preparation of hollow tubes have been devoted, formation of hierarchical shells remains a significant challenge.

EXPERIMENTS

Herein, we demonstrate the fabrication of highly uniform, reproducible and industrially feasible ZnO hollow tubes (ZHT) with two-level hierarchical shells via a simple and versatile single-nozzle electrospinning strategy coupled with subsequent controlled thermal treatment.

FINDINGS

The morphological investigation reveals that the hollow tubes built from nanostructures which has unique surface structure on their wall. The mechanism by which the composite fibers transferred to hollow tubes is primarily based on the evaporation rate of the polymeric template. Notably, tuning the heating rate from 5 °C to 50 °C/min possess adverse effect on formation of hollow tubes, thus subsequently produced ZnO nanoplates (ZNP). The comparative photocatalytic analysis emphasized that ZHT shows higher photocatalytic activity than ZNP. This finding has made an evident that the inherent abundant defects in the electrospun derived nanostructures are not only sufficient for improving the photocatalytic activity. Studies on bacterial growth inhibition showcased a superior bactericidal effect against Staphylococcus aureus and Escherichia coli implying its potentiality for disinfecting the bacteria from water.

Plant-Mediated Biosynthesis and Photocatalysis Activities of Zinc Oxide Nanoparticles: A Prospect towards Dyes Mineralization

In recent years, nanoparticles synthesis by green synthesis has gained extensive attention as a facile, inexpensive, and environmentally friendly method compared with chemical and physical synthesis methods. This review covered the biosynthesis of zinc oxide nanoparticles (ZnO NPs), including the procedure and mechanism. Factors affecting the formation of ZnO NPs are discussed. The presence of active bioorganic molecules in plant extract played a vital role in the formation of ZnO NPs as a natural green medium in the metallic ion reduction processes. ZnO NPs exhibit attractive photocatalysis properties due to electrochemical stability, high electron mobility, and large surface area. In this review, the procedure and mechanism of the ZnO photocatalysis process are studied. The effects of dyes amount, catalysts, and light on photodegradation efficiency are also considered. This review provides useful information for researchers who are dealing with green synthesis of ZnO NPs. Moreover, it can provide investigators with different perceptions towards the efficiency of biosynthesized ZnO NPs on dyes degradation and its restrictions.

Eco-friendly synthesis and photocatalytic application of flowers-like ZnO structures using Arabic and Karaya Gums

Flowers-like ZnO structures were synthesized using Arabic Gum (AGZnO) or Karaya Gum (KGZnO). The AGZnO and KGZnO were characterized by X-ray diffractometry, Fourier Transformed Infrared, Scanning Electron Microscopy, Photoluminescence, nitrogen adsorption/desorption and diffuse reflectance techniques. The materials were tested in the discoloration of Methylene Blue (MB) dye under visible light and scavenger studies were also performed. The toxicity of the MB irradiated was investigated in bioassays with Artemia salina. The structural characterization demonstrated the formation of hexagonal ZnO. All samples presented flower-like morphology with presence of mesopores identified by BET method. The optical properties indicated band gap of 2.99 (AGZnO) and 2.76 eV (KGZnO), and emission in violet, blue and green emissions also were observed. The KGZnO demonstrated better photocatalytic performance than the AGZnO, and scavenger studies indicated that OH radicals are the main species involved in the degradation of the pollutant model. The photodiscoloration of MB solution did not demonstrate toxicity. Therefore, KGZnO is a promising material for photocatalysis application.

A review on biogenic synthesis, applications and toxicity aspects of zinc oxide nanoparticles

Nanoparticles (NPs) have become an important field of research over the past several decades with applications in various sectors, such as biomedical, cosmetic, food and many others, because of their unique characteristics. The green synthesis of nanoparticles has been preferred because of the naturally occurring reductants present in biological systems that decreases exposure to toxic chemicals compared with physico-chemical methods and is eco-friendly. Zinc oxide (ZnO) NPs exhibit broad and potential applications in different fields with their specific characteristics such as surface area, size, shape, low toxicity, optical properties, high binding energy and large band gap. This paper focuses on the bio-synthesis of ZnO NPs by utilizing extracts of different plant parts (stem, flower, fruit, peel, and leaves) through efficient, economical, simple, pure, and eco-friendly green routes. In this process, zinc salts have been used as precursor and phytochemicals in the plant extract reduce the metal salt to lower oxidation state as well as stabilize the ZnO NPs. The morphological and physico-chemical properties of obtained NPs analyzed by various characterization techniques have been discoursed. Further, antimicrobial activity and potential photocatalytic application in terms of the degradation of dyes have also been reviewed in addition to the toxicity aspects of these NPs on human beings and animals.

Cellulose from sources to nanocellulose and an overview of synthesis and properties of nanocellulose/zinc oxide nanocomposite materials

Recently, environmental and ecological concerns are increasing due to the usage of petroleum-based products so the synthesis of ultra-fine chemicals and functional materials from natural resources is drawing a tremendous level of attention. Nanocellulose, a unique and promising natural material extracted from native cellulose, may prove to be most ecofriendly materials that are technically and economically feasible in modern times, minimizing the pollution generation. Nanocellulose has gained tremendous attention for its use in various applications, due to its excellent special surface chemistry, physical properties, and remarkable biological properties (biodegradability, biocompatibility, and non-toxicity). Various types of nanocellulose, viz. cellulose nanofibrils (CNFs), cellulose nanocrystals (CNCs), and bacterial nanocellulose (BNC), are deeply introduced and compared in this work in terms of sources, production, structures and properties. The metal and metal oxides especially zinc oxide nanoparticles (ZnO-NPs) are broadly used in various fields due to the diversity of functional properties such as antimicrobial and ultraviolet (UV) properties. Thus, the advancement of nanocellulose and zinc oxide nanoparticles (ZnO-NPs)-based composites materials are summarized in this article in terms of the preparation methods and remarkable properties with the help of recent knowledge and significant findings (especially from the past six years reports). The nanocellulose materials complement zinc oxide nanoparticles, where they impart their functional properties to the nanoparticle composites. As a result hybrid nanocomposite containing nanocellulose/zinc oxide composite has shown excellent mechanical, UV barrier, and antibacterial properties. The nanocellulose based hybrid nanomaterials have huge potential applications in the area of food packaging, biopharmaceuticals, biomedical, and cosmetics. Thus the functional composite materials containing nanocellulose and zinc oxide will determine the potential biomedical application for nanocellulose.

Coupled Oxides/LLDPE Composites for Textile Effluent Treatment: Effect of Neem and PVA Stabilization

The polyvinyl alcohol (PVA) and neem extract were grafted onto coupled oxides (3ZT-CO) via reflux process to stabilize the particles to form 3ZT-CO/PVA and 3ZT-CO/Neem. These were then incorporated into LLDPE by melt blending process to give LLDPE/3ZT-CO/PVA and LLDPE/3ZT-CO/Neem composites. The Neem and PVA stabilized particles showed high zeta potential and dispersed homogeneously in water. The stabilization process altered the shape of the particles due to plane growth along the (002) polar direction. The stabilizers acted as capping agents and initiated the one-dimensional growth. The alkyl chain groups from PVA increased the polarity of the LLDPE/3ZT-CO/PVA and played a dominant role in the water adsorption process to activate the photocatalytic activity. This was further enhanced by the homogeneous distribution of the particles and low degree of crystallinity (20.87%) of the LLDPE composites. LLDPE/3ZT-CO/PVA exhibited the highest photodegradation (93.95%), which was better than the non-stabilized particles. Therefore, the photocatalytic activity of a polymer composite can be enhanced by grafting PVA and neem onto couple oxides. The LLDPE/3ZT-CO/PVA composite was further used to treat textile effluent. The results showed the composite was able to remove dye color by 93.95% and to reduce biochemical oxygen demand (BOD) and chemical oxygen demand (COD) by 99.99%.

Controlling the morphology of metal–organic frameworks and porous carbon materials: metal oxides as primary architecture-directing agents

We give a comprehensive overview of how the morphology control is an effective and versatile way to control the physicochemical properties of metal oxides that can be transferred to metal–organic frameworks and porous carbon materials.