Novel seaweed capped ZnO nanoparticles for effective dye photodegradation and antibacterial activity

Bioactive nanoparticles derived from marine brown seaweeds and their biological applications: a review

The biosynthesis of novel nanoparticles with varied morphologies, which has good implications for their biological capabilities, has attracted increasing attention in the field of nanotechnology. Bioactive compounds present in the extract of fungi, bacteria, plants and algae are responsible for nanoparticle synthesis. In comparison to other biological resources, brown seaweeds can also be useful to convert metal ions to metal nanoparticles because of the presence of richer bioactive chemicals. Carbohydrates, proteins, polysaccharides, vitamins, enzymes, pigments, and secondary metabolites in brown seaweeds act as natural reducing, capping, and stabilizing agents in the nanoparticle's synthesis. There are around 2000 species of seaweed that dominate marine resources, but only a few have been reported for nanoparticle synthesis. The presence of bioactive chemicals in the biosynthesized metal nanoparticles confers biological activity. The biosynthesized metal and non-metal nanoparticles from brown seaweeds possess different biological activities because of their different physiochemical properties. Compared with terrestrial resources, marine resources are not much explored for nanoparticle synthesis. To confirm their morphology, characterization methods are used, such as absorption spectrophotometer, X-ray diffraction, Fourier transforms infrared spectroscopy, scanning electron microscope, and transmission electron microscopy. This review attempts to include the vital role of brown seaweed in the synthesis of metal and non-metal nanoparticles, as well as the method of synthesis and biological applications such as anticancer, antibacterial, antioxidant, anti-diabetic, and other functions.

Zinc oxide-Ulva lactuca nanocomposite is a robust dietary immunostimulant in the red swamp crayfish (Procambarus clarkii)

Aquaculture industry suffers significant limitations such as low resistance to diseases and expensive feed. This study investigated the antibacterial and immunostimulatory activities of ZnO-Ulva lactuca nanocomposite (ZnO-Ul NC) in the Procambarus clarkii. Zinc oxide nanoparticles (ZnO NPs) and ZnO-Ul NC were synthetized and characterized by electron microscopies as well as Fourier transform infrared spectroscopy. ZnO NPs and ZnO-Ul NC inhibited the growth of the isolated species Citrobacter freundii and Enterobacter hormaechei. For immunostimulatory evaluation, six crayfish groups (control, U. lactuca, ZnO L, ZnO H, ZnO-Ul L, and ZnO-Ul H) were fed on commercial diet, Ulva lactuca powder, and low or high dose of ZnO NPs or ZnO-Ul NCs, respectively for 90 days. The highest levels of total hemocyte count, granular cells%, phenoloxidase (PO) activity in hemolymph, and NO, superoxide dismutase (SOD), and GSH in hepatopancreas were all reported in the ZnO-Ul groups. The expression of proPO, SOD, and lysozyme exhibited the highest upregulation in the ZnO-Ul H group. Taken together, dietary ZnO-Ul NC significantly improved the non-specific immunity and antioxidant milieu of the crayfish at the genomic and proteomic levels. ZnO-Ul NC is cost effective, easily synthesized, and a promising immunostimulant for Procambarus clarkii that could be used in the aquaculture.

Imine-Decorated Copper-Based Metal-Organic Framework for the Photodegradation of Methylene Blue

A low cost imine-decorated linker, 4,4'-(hydrazine-1,2-diylidenedimethylylidene)dibenzoic acid was utilized for the preparation of copper-based metal-organic framework (MOF) denoted as Cu-L via a solvothermal technique. The synthesized MOF material has been fully characterized by different analytical techniques such as Fourier-transform infrared (FT-IR) spectroscopy, powder X-Ray diffraction (PXRD), scanning electron microscopy (SEM), energy dispersive X-Ray spectroscopy (EDX), nitrogen adsorption-desorption isotherm analysis, and thermogravimetric analysis (TGA). It has been found that the coordination of Cu2+ with L considerably reduced the band gap of the L of nearly about 1 eV, which is approximately 26% decline in total. Notably, a narrow band gap of the photocatalyst is an essential requirement for the proficient photodegradation of organic contaminants. An excellent optical properties and narrow band gap of (2.8 eV) of Cu-L ensure their suitability as a photocatalyst for the degradation of methylene blue (MB) dye. In the presence of Cu-L photocatalyst, 84.22% degradation of MB dye was observed after 150 min under sunlight exposure. It is the first time that imine-functionalized MOF was utilized for the degradation of MB dye under sunlight irradiation. For understanding the photodegradation of MB dye by the Cu-L photocatalyst, all the plausible mechanistic studies have been carried out in detail. Both theoretical (with the help of density functional theory (DFT) calculations) as well as experimental studies have been conducted to justify the possible mechanisms for the photodegradation of MB dye by Cu-L. The current work may open a new opportunity to construct a cheap MOF-based photocatalysts for fast degradation of dye contaminants.

Galactomannan polysaccharide as a biotemplate for the synthesis of zinc oxide nanoparticles with photocatalytic, antimicrobial and anticancer applications

Biotemplates provide a facile, rapid, and environmentally benign route for synthesizing various nanostructured materials. Herein, Locust Bean Gum (LBG), a galactomannan polysaccharide, has been used as a biotemplate for synthesizing ZnO nanoparticles (NPs) for the first time. The composition, structure, morphology, and bandgap of ZnO were investigated by Energy Dispersive X-ray Spectroscopy (EDX), X-Ray Photoelectron Spectroscopy (XPS), X-ray powder diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and UV-vis spectroscopy. XRD data showed single-phase crystalline hexagonal NPs. FTIR spectra confirmed the presence of M-O bonding in the sample. At a concentration of 0.5 mg/mL the NPs can degrade Rhodamine B under sunlight, displaying excellent photocatalytic activity. These NPs exhibited antimicrobial activity in both Staphylococcus aureus and Bacillus subtilis. Significant cell death was observed at 500 μg/mL, 250 μg/mL, 125 μg/mL and 62.5 μg/mL of NP in breast cancer, ovarian cancer and lung cancer cell lines. Wound healing assay showed that the NPs significantly blocked the cell migration at a concentration as low as 62.5 μg/mL in all three cell lines. Further optimization of the nanostructure properties will make it a promising candidate in the field of nano-biotechnology and bioengineering owing to its wide range of potential applications.

Evaluation of antimicrobial and antioxidant activity of zinc oxide nanoparticles biosynthesized with Ziziphus spina-christi leaf extracts

Background: Due to their simplicity, eco-friendliness, availability and non-toxicity, the greener fabrication of metal and metal oxide nanoparticles has been a highly attractive research area over the last decade. Aim: This study aimed to assess the antioxidant and antimicrobial activities of the green synthesized zinc oxide nanoparticles (ZnO-NPs) using an aqueous leaf extract of Ziziphus spina-christi. Method: The antioxidant property of ZnO-NPs was analyzed by the α, α-diphenyl-β-picrylhydrazyl (DPPH) and hydrogen peroxide (H2O2). Additionally, the diffusion agar method assessed the antimicrobial activities against bacteria and fungi. Results: ZnO-NPs synthesized by Z. spina-christi had shown promising H2O2 and DPPH free radical scavenging actions compared to vitamin C. The ZnO-NPs exhibited significant antibacterial activity against the tested bacteria with various susceptibility as a concentration-dependent effect. The largest zone of inhibition for Staphylococcus aureus (S. aureus) was observed (36 ± 2 mm) compared to Escherichia coli (E. coli) (15 ± 2 mm) by the same concentration of ZnO-NPs. The ZnO-NPs showed remarkable antifungal activity against Aspergillus niger. Conclusion: It can be concluded that, ZnO-NP have been imposed as suitable antimicrobial agent being able to combat both S. aureus and E. coli in vitro.

Recent advances in the synthesis, characterization and biomedical applications of zinc oxide nanoparticles

Zinc oxide nanoparticles (ZnONPs) have become the widely used metal oxide nanoparticles and drawn the interest of global researchers due to their biocompatibility, low toxicity, sustainability and cost-effective properties. Due to their unique optical and chemical properties, it emerges as a potential candidate in the fields of optical, electrical, food packaging and biomedical applications. Biological methods using green or natural routes are more environmentally friendly, simple and less use of hazardous techniques than chemical and/or physical methods in the long run. In addition, ZnONPs are less harmful and biodegradable while having the ability to greatly boost pharmacophore bioactivity. They play an important role in cell apoptosis because they enhance the generation of reactive oxygen species (ROS) and release zinc ions (Zn2+), causing cell death. Furthermore, these ZnONPs work well in conjunction with components that aid in wound healing and biosensing to track minute amounts of biomarkers connected to a variety of illnesses. Overall, the present review discusses the synthesis and most recent developments of ZnONPs from green sources including leaves, stems, bark, roots, fruits, flowers, bacteria, fungi, algae and protein, as well as put lights on their biomedical applications such as antimicrobial, antioxidant, antidiabetic, anticancer, anti-inflammatory, antiviral, wound healing, and drug delivery, and modes of action associated. Finally, the future perspectives of biosynthesized ZnONPs in research and biomedical applications are discussed.

Analysis of natural photocatalysts derived from spartina alterniflora with superior removal performance of pollutant

Spartina alterniflora, as an invasive alien species, has been studied in terms of its potential use in immobilization and synergistic photocatalysis against dye contaminants for the first time. Microscopic characterization and Fourier transform infrared (FTIR) spectroscopy results confirmed the presence of abundant 3D wormhole-like pore structures and active functional groups (-OH, -NH2, CO, Si-O-Si). Moreover, the existence of SiO2 was connected the metal oxides with polar groups, which could proceed entire reaction procedure subsequently. Transition metal oxides (such as Fe2O3, TiO2, MnO2 and NiO) contained in photocatalysts might effectively promote the organics decomposition by the visible light excitation. The highest dye removal efficiency of 92.03% could be reached with the addition of 0.02 g photocatalyst. The capture experiment confirmed that the h+ was the dominant active substance during the photocatalytic degradation process. Density functional theory (DFT) calculations verified that the functional groups (-COOH, -OH and -NH2) were exceptional adsorption sites for catalyst, and the calculated adsorption energy were all negative with the order of SRHH-NH2 (-2.712688 eV) < SRHH-OH (-2.075601 eV) < SRHH-COOH (-1.283141 eV), which confirmed that interface interaction effectively bound cationic dyes through the formation of hydrogen bonds at the catalysts-water interface, further accelerating the reaction rate of the entire photocatalytic reduction of dye molecules. Therefore, this work provides a feasible synthesis of natural photocatalysts using solid waste, which suggests excellent adsorption and photocatalysis properties for the treatment of organic industrial pollutant.

Hybrid nanostructures exhibiting both photocatalytic and antibacterial activity-a review

The most vital issues of the modern world for a sustainable future are "health" and "the environment." Scientific endeavors to tackle these two major concerns for mankind need serious attention. The photocatalytic activity toward curbing environmental pollution and antibacterial performance toward a healthy society are two directions that have been emphasized for decades. Recently, materials engineering, in their nanodimension, has shown tremendous possibilities to integrate these functionalities within the same materials. In particular, hybrid nanostructures have shown magnificent prospects to combat both crucial challenges. Many researchers are separately engaged in this important field of research but the collective knowledge on this domain which can facilitate them to excel is badly missing. The present article integrates the development of different hybrid nanostructures which exhibit both photocatalytic degradations of environmental pollutants and antibacterial efficiency. Various synthesis techniques of those hybrid nanomaterials have been discussed. Hybrid nanosystems based on several successful materials have been categorically discussed for better insight into the research advancement in this direction. In particular, Ag-based, metal oxides-based, layered carbon material-based, and Mexene- and self-cleaning-based materials have been chosen for detailing their performance as anti-pollutant and antibacterial materials. Those hybrid systems along with some miscellaneous booming nanostructured materials have been discussed comprehensively with their success and limitations toward their bifunctionality as antipollutant and antibacterial agents.

Combined toxic effects of environmental predominant microplastics and ZnO nanoparticles in freshwater snail Pomaceae paludosa

In the past few years, microplastics are one of the ubiquitous threatening pollutants in aquatic habitats. These persistent microplastics interact with other pollutants, especially nanoparticles were adherent on the surface, which causes potential hazards in the biota. In this study, the toxic effects of individual and combined (28 days) exposure with zinc oxide nanoparticles and polypropylene microplastics were assessed in freshwater snail Pomeacea paludosa. After the experiment, the toxic effect was evaluated by the estimation of vital biomarkers activities including antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), oxidative stress in carbonyl protein (CP), lipid peroxidation (LPO), and digestive enzymes (esterase and alkaline phosphatase). Chronic exposure to pollutants in snails causes increased reactive oxygen species level (ROS) and generates free radicals in their body which leads to impairment and alterations of biochemical markers. Where alteration in acetylcholine esterase (AChE) activity and decreased digestive enzymes (esterase and alkaline phosphatase) activities were observed in both individual and combined exposed groups. Further, histology results revealed the reduction of haemocyte cells, the disintegration of blood vessels, digestive cells, calcium cells, and DNA damage was also detected in the treated animals. Overall, when compared to individual exposures, combined exposure of pollutants (zinc oxide nanoparticles and polypropylene microplastics) causes more serious harms including decline and increased antioxidant enzyme parameters, damage the protein and lipids by oxidative stress, increased neurotransmitter activity, decrease digestive enzyme activities in the freshwater snail. The outcome of this study concluded that polypropylene microplastics along with nanoparticles cause severe ecological threats and physio-chemical effects on the freshwater ecosystem.

Integrated adsorption and photocatalytic degradation based removal of ciprofloxacin and sulfamethoxazole antibiotics using Fc@rGO-ZnO nanocomposite in aqueous systems

Ferrocene functionalized rGO-ZnO nanocomposite was synthesized via the facile hydrothermal method. ZnO was reduced over the 3-dimensional rGO framework (3D-Fc@rGO) using Camellia sinensis extract. The Fc@rGO-ZnO nanocomposite was employed for pharmaceutical degradation (sulfamethoxazole (SMX) and ciprofloxacin (CIP)) in an aqueous solution under UV C light. The physicochemical properties of the as-prepared photocatalyst were characterized using FTIR, XRD, FESEM, EDS mapping, HR-TEM, XPS, and DR-UV Vis. The as-synthesized Fc@rGO-ZnO photocatalyst performed remarkably against pristine ZnO, with a fivefold increase in removal efficiency. This superior activity was attributed to its improved light harvesting, charge carrier interface, and enhanced charge separation. Additionally, the photocatalyst obeyed the Lagergen model for pseudo-first-order kinetics. Congruously, the integrated approach of Fc@rGO and ZnO as oxidizing agents was proficient in removing >95% of antibiotics (CIP and SMX) within 180 min. Furthermore, the heterostructure configuration developed between Fc@rGO and ZnO helps in charge migration and generation of abundant •OH and •O₂^- radicals for photodegradation activities. The toxicity assessment of the treated solutions showed improved cell viability in the algal strains of Scenedesmus and Chlorella sp. Moreover, this novel approach for the synthesis of a photoactive nanocomposite is found to be low-cost and reusable for three cycles. The nanocomposite is environmentally sustainable paving the way for practical applications in the treatment of different classes of antibiotics.

Algal Extracts for Green Synthesis of Zinc Oxide Nanoparticles: Promising Approach for Algae Bioremediation

Zinc oxide nanoparticles (ZnO-NPs) possess unique properties, making them a popular material across various industries. However, traditional methods of synthesizing ZnO-NPs are associated with environmental and health risks due to the use of harmful chemicals. As a result, the development of eco-friendly manufacturing practices, such as green-synthesis methodologies, has gained momentum. Green synthesis of ZnO-NPs using biological substrates offers several advantages over conventional approaches, such as cost-effectiveness, simplicity of scaling up, and reduced environmental impact. While both dried dead and living biomasses can be used for synthesis, the extracellular mode is more commonly employed. Although several biological substrates have been successfully utilized for the green production of ZnO-NPs, large-scale production remains challenging due to the complexity of biological extracts. In addition, ZnO-NPs have significant potential for photocatalysis and adsorption in the remediation of industrial effluents. The ease of use, efficacy, quick oxidation, cost-effectiveness, and reduced synthesis of harmful byproducts make them a promising tool in this field. This review aims to describe the different biological substrate sources and technologies used in the green synthesis of ZnO-NPs and their impact on properties. Traditional synthesis methods using harmful chemicals limit their clinical field of use. However, the emergence of algae as a promising substrate for creating safe, biocompatible, non-toxic, economic, and ecological synthesis techniques is gaining momentum. Future research is required to explore the potential of other algae species for biogenic synthesis. Moreover, this review focuses on how green synthesis of ZnO-NPs using biological substrates offers a viable alternative to traditional methods. Moreover, the use of these nanoparticles for industrial-effluent remediation is a promising field for future research.

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.

Investigation of morphological and biochemical changes of zinc oxide nanoparticles induced toxicity against multi drug resistance bacteria

BACKGROUND

Biofilms are microbial colonies that remain enclosed in an organic polymeric matrix substance on biotic and abiotic surfaces, allowing them to colonize medical equipments and involved in most device associated life intimidating infections. Due to their antimicrobial resistance there is an urgent need to discover novel biofilm preventive and therapeutic agents.

METHODS

ZnO NPs were synthesized using cyanobacteria Gleocapsa gelatinosa cell extract through green and cost-effective approach. Physiochemical characterization was done to determine their morphologies and size distribution. Antibiofilm and eradication activity of ZnO NPs was determined. Cell viability and internalization ability of ZnO NPs into biofilm was analyzed by flow cytometry. Confocal microscopy was done to visualize the disrupted biofilm morphology treated with ZnO NPs.

RESULTS

It was observed that ZnONPs were spherical in shape with 31-35 nm size and were moderately dispersed. ZnO NPs exhibited high antibiofilm activity against B. cereus and E. coli with minimum biofilm inhibitory concentration (MBIC) of ZnO NPs at 46.8 µg ml^-1 and 93.7 µg ml^-1. Flow cytometry analysis confirmed the reduced bacterial cell viability due to increased permeability, altered bacterial growth and enhanced production of intracellular ROS. Disruption of membrane integrity exhibited with reduced exopolysaccharides secretion and leakage of nucleic acids through UV-Vis spectroscopy. Results of confocal microscopy highlighted strong interaction of ZnO NPs with intracellular components leading to biofim destruction.

CONCLUSIONS

This study emphasizes the potential mechanisms underlying the selective bactericidal properties of ZnO NPs and highlighted the strong interaction of ZnO NPs with intracellular components leading to biofim destruction. Therefore, ZnO NPs could be considered as a promising antibiofilm agent and thus could expand the possibility to use as therapeutic agent.

Zinc Oxide Nanoparticles and Their Application in Adsorption of Toxic Dye from Aqueous Solution

Dye waste is one of the most serious types of pollution in natural water bodies, since its presence can be easily detected by the naked eye, and it is not easily biodegradable. In this study, zinc oxide nanoparticles (ZnO-NPs) were generated using a chemical reduction approach involving the zinc nitrate procedure. Fourier transform infrared (FTIR), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), and UV-vis techniques were used to analyse the surface of ZnO-NPs. The results indicate the creation of ZnO-NPs with a surface area of 95.83 m2 g−1 and a pore volume of 0.058 cm3 g−1, as well as an average pore size of 1.22 nm. In addition, the ZnO-NPs were used as an adsorbent for the removal of Ismate violet 2R (IV2R) dye from aqueous solutions under various conditions (dye concentration, pH, contact time, temperature, and adsorbent dosage) using a batch adsorption technique. Furthermore, FTIR and SEM examinations performed before and after the adsorption process indicated that the surface functionalisation and shape of the ZnO-NP nanocomposites changed significantly. A batch adsorption analysis was used to examine the extent to which operating parameters, the equilibrium isotherm, adsorption kinetics, and thermodynamics affected the results. The results of the batch technique revealed that the best results were obtained in the treatment with 0.04 g of ZnO-NP nanoparticles at 30 °C and pH 2 with an initial dye concentration of 10 mg L−1, which removed 91.5% and 65.6% of dye from synthetic and textile industry effluents, respectively. Additionally, six adsorption isotherm models were investigated by mathematical modelling and were validated for the adsorption process, and error function equations were applied to the isotherm model results in order to find the best-fit isotherm model. Likewise, the pseudo-second-order kinetic model fit well. A thermodynamic study revealed that IV2R adsorption on ZnO-NPs is a spontaneous, endothermic, and feasible sorption process. Finally, the synthesised nanocomposites prove to be excellent candidates for IV2R removal from water and real wastewater systems.

Green Synthesis of Zinc Oxide Nanoparticles Using Red Seaweed for the Elimination of Organic Toxic Dye from an Aqueous Solution

This study aims to produce green zinc oxide nanoparticles (ZnO-NPs) derived from red seaweed (Pterocladia Capillacea) and evaluate their potential to absorb Ismate violet 2R (IV2R) ions from an aqueous solution. UV-vis spectrophotometry, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and a Brunauer-Emmett-Teller surface area analysis (BET) were used to analyze the structural, morphological, and optical features of the synthesized nanoparticles. The change in color of the chemical solution revealed the formation of zinc oxide nanoparticles. The FTIR examination confirmed the synthesis of both Zn and ZnO nanoparticle powder, with a BET surface area of 113.751 m² g^-1 and an average pore size of 2.527 nm for the synthesized adsorbent. Furthermore, the maximum removal effectiveness of IV2R was 99% when 0.08 g ZnO-NPs was applied at a pH of 6, a temperature of 55 °C, and a contact time of 120 min. The dye adsorption capacity of the ZnO-NPs was 72.24 mg g^-1. The adsorption process was also controlled by the Freundlich adsorption model and pseudo-second-order reaction kinetics. The adsorption of IV2R ions onto the ZnO-NPs could be represented as a nonideal and reversible sorption process of a nonuniform surface, according to Freundlich adsorption isotherms. In addition, the constant values of the model parameters were determined using various nonlinear regression error functions. Moreover, thermodynamic parameters such as entropy change, enthalpy change, and free energy change were investigated; the adsorption process was spontaneous and endothermic. The high capacity of the ZnO-NPs synthesized by red seaweed promotes them as promising substances for applications in water treatment for the removal of IV2R dye from aqueous systems.

Phyco-Synthesized Zinc Oxide Nanoparticles Using Marine Macroalgae, Ulva fasciata Delile, Characterization, Antibacterial Activity, Photocatalysis, and Tanning Wastewater Treatment

The aqueous extract of marine green macroalgae, Ulva fasciata Delile, was harnessed for the synthesis of zinc oxide nanoparticles (ZnO-NPs). The conversion to ZnO-NPs was characterized by color change, UV–vis spectroscopy, FT-IR, TEM, SEM-EDX, and XRD. Data showed the formation of spherical and crystalline ZnO-NPs with a size range of 3–33 nm. SEM-EDX revealed the presence of Zn and O in weight percentages of 45.3 and 31.62%, respectively. The phyco-synthesized ZnO-NPs exhibited an effective antibacterial activity against the pathogenic Gram-positive and Gram-negative bacteria. The bacterial clear zones ranged from 21.7 ± 0.6 to 14.7 ± 0.6 mm with MIC values of 50–6.25 µg mL−1. The catalytic activity of our product was investigated in dark and visible light conditions, using the methylene blue (MB) dye. The maximum dye removal (84.9 ± 1.2%) was achieved after 140 min in the presence of 1.0 mg mL−1 of our nanocatalyst under the visible light at a pH of 7 and a temperature of 35 °C. This percentage was decreased to 53.4 ± 0.7% under the dark conditions. This nanocatalyst showed a high reusability with a decreasing percentage of ~5.2% after six successive cycles. Under the optimum conditions, ZnO-NPs showed a high efficacy in decolorizing the tanning wastewater with a percentage of 96.1 ± 1.7%. Moreover, the parameters of the COD, BOD, TSS, and conductivity were decreased with percentages of 88.8, 88.5, 96.9, and 91.5%, respectively. Moreover, nano-ZnO had a high efficacy in decreasing the content of the tanning wastewater Cr (VI) from 864.3 ± 5.8 to 57.3 ± 4.1 mg L−1 with a removal percentage of 93.4%.

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.

Studies on the removal of acid violet 7 dye from aqueous solutions by green ZnO@Fe3O4 chitosan-alginate nanocomposite synthesized using Camellia sinensis extract

In the present study, ZnO-Fe₃O₄ nanoparticles were synthesized using the leaves of Camellia sinensis and immobilized in crosslinked alginate-chitosan polymer beads and tested for their photocatalytic applications. The prepared nanocomposite was used for the simultaneous adsorption and photocatalytic degradation of acid violet 7 (AV7) dye. The optimization of reaction conditions ensured higher dye removal efficacy up to 94.21 ± 1.02% using the nanocomposite under UV-C irradiation of 365 nm. The kinetics of the adsorption study fitted well with the pseudo-first-order reaction. The Langmuir model fitted better to the adsorption isotherms compared to the Freundlich and Temkin models. The mechanism of degradation was studied by analyzing the treated AV7 solution. The removal efficiency in tap water, groundwater, and lake water was 83.23 ± 0.4%, 69.13 ± 1.6%, and 67.89 ± 0.3%, respectively. The residual toxicity of the degraded AV7 solution was tested on model organisms like freshwater algae, Scenedesmus sp., and plant model, Allium cepa, demonstrating the lower toxicity of the degraded AV7 product. Finally, a cost-benefit analysis of the experiments was also carried out.

Synthesis of photocatalytic zinc oxide nanoflowers using Peltophorum pterocarpum pod extract and their characterization

Zinc oxide nanoflowers (ZnONFs) were prepared by employing the pod extract of Peltophorum pterocarpum as a green resource and characterized by various methods. UV–vis spectrum displayed a peak at 361 nm which confirmed the formation of ZnO nanoparticles. The optical band gap was calculated as 3.43 eV. FE-SEM images exposed the flower-like morphology and EDX portrayed strong signals for Zn and O. XRD studies substantiated signature peaks for the wurtzite phase of ZnONFs and the lattice parameters matched well with the literature. Mesoporous nature was confirmed by BET analysis which yielded a high specific surface area of 19.61 m2/g. FTIR bands at 420.48 and 462.92 cm−1affirmed the Zn and O bonding vibrations. The photocatalytic potential of the ZnONFs was successfully examined for the removal of methylene blue dye under natural solar light. The experimental data were fitted to Langmuir–Hinshelwood’s first-order equation and the kinetic constant was calculated as 0.0114 min–1.

Biofabrication and characterization of cyanobacteria derived ZnO NPs for their bioactivity comparison with commercial chemically synthesized nanoparticles

Due to unique properties of the nanoparticles (NPs) with biocompatibility, their application as drug in drug delievery and diagnostics, the recent scientific branch nanotechnology has emerged as hope in modern medicine. Zinc oxide nanoparticles (ZnO NPs) have gained tremendous interest due to their potential use as chemotherapeutic and antimicrobial agents. They are included in the category of "generally recognized as safe (GRAS) metal oxide". There is an urgent need for developing additional sources of ZnO NPs. Therefore, in the present study 30 cyanobacterial extracts were screened for ZnO NPs synthesis.. The color change of the reaction mixture from blue to pale white indicated the synthesis of ZnO NPs. It was further confirmed by UV-Visible spectroscopy that showed the absorption peak at 372 nm. The SEM analysis during screening revealed that Oscillatoria sp. synthesized smallest ZnO NPs (~40 nm) that were further optimized for their higher yield by altering reaction conditions (pH, temperature, reaction time, concentration of extract and metal precursor). Best conditions for ZnO NPs synthesis are (0.02 M zinc nitrate, 10 ml of extract volume, pH 8, at 80 °C for 3 h). The NPs were purified through calcination at 350°C and characterized by UV-Vis, FTIR, XRD, SEM-EDAX, TEM, Zeta potential and DLS analysis. The comparative analysis of purified biogenic ZnO NPs with commercial chemically synthesized ZnO NPs (CS), exhibited their superior nature as antioxidant and anti-bacterial agent against both gram-positive and gram-negative bacteria. Synergistic effects of biogenic ZnO NPs and streptomycin additionally favored for their future use as a potential biomedical agent.

Comparative study of chemically synthesized and low temperature bio-inspired Musa acuminata peel extract mediated zinc oxide nanoparticles for enhanced visible-photocatalytic degradation of organic contaminants in wastewater treatment

Zinc oxide (ZnO) photocatalysts were successfully synthesized via chemical and green, environmentally-benign methods. The work highlights the valorization of banana peel (BP) waste extract as the reducing and capping agents to produce pure, low temperature, highly crystalline, and effective ZnO nanoparticles with superior photocatalytic activities for the removal of hazardous Basic Blue 9 (BB9), crystal violet (CV), and cresol red (CR) dyes in comparison to chemically synthesized ZnO. Their formation and morphologies were verified by various optical spectroscopic and electron microscopic techniques. XRD results revealed that the biosynthesized ZnO exhibited 15.3 nm crystallite size when determined by Scherrer equation, which was smaller than the chemically synthesized ZnO. The FTIR spectra confirmed the presence of biomolecules in the green-mediated catalyst. EDX and XPS analyses verified the purity and chemical composition of ZnO. Nitrogen sorption analysis affirmed the high surface area of bio-inspired ZnO. Maximum removal efficiencies were achieved with 30 mg green ZnO catalyst, 2.0 × 10^-5 M BB9 solution, alkaline pH 12, and irradiation time 90 min. Green-mediated ZnO showed superior photodegradation efficiency and reusability than chemically synthesized ZnO. Therefore, this economical, environment-friendly photocatalyst is applicable for the removal of organic contaminants in wastewater treatment under visible light irradiation.

Therapeutic Potential of Green Synthesized Metallic Nanoparticles against Staphylococcus aureus

BACKGROUND

The recent treatment challenges posed by the widespread emergence of pathogenic Multidrug-Resistant (MDR) bacterial strains are a cause of huge health troubles worldwide. Infections caused by MDR organisms are associated with longer period of hospitalization, increased mortality, and inflated healthcare costs. Staphylococcus aureus is one of these MDR organisms identified as an urgent threat to human health by the World Health Organization. Infections caused by S. aureus may range from simple cutaneous infestations to life threatening bacteremia. S. aureus infections get easily escalated in severely ill, hospitalized and or immunocompromised patients with incapacitated immune system. Also, in HIV-positive patients S. aureus ranks amongst one of the most common comorbidities where it can further worsen a patient's health condition. At present anti-staphylococcal therapy is reliant typically on chemotherapeutics that are gathering resistance and pose unfavorable side-effects. Thus, newer drugs are required that can bridge these shortcomings and aid effective control against S. aureus.

OBJECTIVE

In this review, we summarize drug resistance exhibited by S. aureus and lacunae in current anti-staphylococcal therapy, nanoparticles as an alternative therapeutic modality. The focus lays on various green synthesized nanoparticles, their mode of action and application as potent antibacterial compounds against S. aureus.

CONCLUSION

Use of nanoparticles as anti-bacterial drugs has gained momentum in recent past and green synthesized nanoparticles, which involves microorganisms and plants or their byproducts for synthesis of nanoparticles offer a potent, as well as environment friendly solution in warfare against MDR bacte.

Photocatalytic degradation of methyl orange using pullulan-mediated porous zinc oxide microflowers

One of mankind's biggest concerns is water pollution. Textile industry emerged as one of the main contributors with dyes as the main pollutant. Presence of dyes in water is very dangerous due to their toxicity; thus, it is important to remove them from water. In these recent years, heterogeneous advance oxidation process surfaced as a possible dyes' removal technique. This process utilizes semiconductor as photocatalyst to degrade the dyes in presence of light and zinc oxide (ZnO) appears to be a promising photocatalyst for this process. In this study, pullulan, a biopolymer, was used to produce porous ZnO microflowers (ZnO-MFs) through green synthesis via precipitation method. The effects of pullulan's amount on the properties of ZnO-MFs were investigated. The ZnO-MF particle size decreased with the increased of pullulan amount. Interestingly, formation of pores occurred in presence of pullulan. The synthesized ZnO-MFs have the surface area ranging from 6.22 to 25.65 m² g^-1 and pore volume up to 0.1123 cm³ g^-1. The ZnO-MF with the highest surface area was chosen for photocatalytic degradation of methyl orange (MO). The highest degradation occurred in 300 min with 150 mg catalyst dosage, 10 ppm initial dye concentration, and pH 7 experimental conditions. However, through comparison of photodegradation of MO with all synthesized ZnO-MFs, 25PZ exhibited the highest degradation rate. This shows that photocatalytic activity is not dependent on surface area alone. Based on these results, ZnO-MF has the potential to be applied in wastewater treatment. However, further improvement is needed to increase its photocatalytic activity.

Polyphenol Enriched Extract of Pomegranate Peel; A Novel Precursor for the Biosynthesis of Zinc Oxide Nanoparticles and Application in Sunscreens

Background: Green synthesized nanoparticles (NPs) from agricultural wastes is an area of great interest due to it is eco-friendly and profitable. Zinc oxide is an inorganic UV-filter commonly used as UV-blocker in a different industry. Methods: Zinc oxide nanoparticles (ZnO NPs) were successfully biosynthesized using Zn(NO3)2 as a substrate by polyphenol enriched fraction (PEF) of pomegranate peel. The biological activity of ZnO NPs was evaluated using MBC and MIC tests for antibacterial and DPPH assay for antioxidant potential. Sunscreen potential of NPs was determined after applying them in water-in-oil emulsions. Results: UV-Vis and FT-IR spectroscopy techniques confirmed the formation of ZnO NPs. FE-SEM characterized the morphology and purity of the biosynthesized NPs with EDAX and XRD data. The average crystalline size of ZnO NPs was found to be 22 nm. FT-IR spectroscopy revealed the role of phenolic compounds in the formation and stability of ZnO NPs. The antibacterial activity of PEF and its biosynthesized ZnO was evaluated against Staphylococcus aureus and Escherichia coli. The prepared NPs showed a higher antibacterial effect than the commercial ZnO NPs. Interestingly, the antioxidant activity was also detected for obtained NPs. The PEF powder also exhibited higher antibacterial and antioxidant activity than the standards. Furthermore, the in vitro sun protection factors were estimated after applying NPs in water-in-oil emulsions. Conclusion: This study highlighted the possibility of using PEF of pomegranate peel for the biosynthesis of ZnO NPs as well as applying its NPs in sunscreens to achieve a safe alternative to harmful chemical UV-filters commonly used in cosmetics.

Enhanced solar water disinfection using ZnO supported photocatalysts

Nano-structured ZnO photocatalysts on cellulose and polyester supports were developed for enhancing solar water disinfection (SODIS). The photocatalysts were fabricated by a two-step hydrothermal method, in which ZnO nanoparticles were synthesized and deposited on a cellulose or polyester support as a seed layer, followed by the growth of one-dimensional ZnO nanorods on the seed layer in a liquid bath containing zinc nitrate and hexamethylenetetramine as sources of precursors. The morphologies and phase compositions of the synthesized ZnO nanorods from different growth conditions were investigated with field emission scanning electron microscope and X-ray diffraction (XRD), respectively. The crystallinity size of the ZnO nanorods was in the range of 17-30 nm and increased with the precursor concentration. The XRD patterns also revealed that higher growth solution concentrations led to higher intensity of XRD peaks, indicating higher crystallinity. Additionally, to test for SODIS enhancement, experiments using 200-mL transparent polyethylene bags as SODIS reactors, with ZnO photocatalysts inside, and water samples containing 10⁶ CFU of Escherichia Coli were conducted in a laboratory UVA setup. The photocatalyst with a polyester support resulted in a 15% higher disinfection efficiency than that of the one with a cellulose support. Moreover, a field test of enhanced SODIS was conducted in actual sunlight, using specially designed SODIS reactors containing ZnO photocatalysts with a polyester support. Nearly total disinfection (97-98% efficiency) was achieved within the first 15 min of every test. The treated water was also tested for zinc contents, which could be released from the photocatalysts, by ICP-OES. The results were lower than 2 mg/L.

Biosorption of Direct Fast Scarlet 4BS from aqueous solution using the green-tide-causing marine algae Enteromorpha prolifera

Enteromorpha prolifera, the marine algae frequently causing green tide in the littoral areas in recent years, was investigated as a feasible biosorbent to remove azo dye Direct Fast Scarlet 4BS (DFS-4BS) from aqueous solution. The FTIR spectra of the acid-treated Enteromorpha prolifera (ATEP) biomass before and after dye sorption were used to identify the main functionalities involved in the biosorption process. Results of batch experiments showed that the adsorption capacity of ATEP was dependent on solution pH, ATEP dosage and temperature. The adsorption kinetics followed the pseudo-second order rate equation, while the adsorption isotherm could be well described by the Langmuir model with maximum sorption capacity of 318.87mg·g^-1, demonstrating the excellent performance of ATEP as a biosorbent to remove DFS-4BS from aqueous solution. The negative values of free energy change (ΔG°) and positive value of enthalpy change (ΔH°) confirmed that the sorption of DFS-4BS onto ATEP was spontaneous and endothermic in the temperature range of 303-333K. The isosteric heat of adsorption increased with the increase of surface loading, suggesting that the ATEP biomass had heterogeneous surface and lateral interactions might exist among adsorbed molecules. According to the sorption results and the FTIR spectra, it was deduced that the adsorption mechanism involved hydrogen bonding, electrostatic attraction and bonding, and hydrophobic and van der Waals interaction.

In-vivo and in-vitro tests to assess toxic mechanisms of nano ZnO to earthworms

Increasing applications of engineered nanomaterials lead to the release of nanoparticles into various environmental media, especially soil. However, the environmental behavior of nano ZnO in soil and the toxic mechanism to terrestrial invertebrates were not fully understood. In this study, the concentrations of nano ZnO in earthworms (Eisenia fetida) were measured to assess its bioaccumulation. The ratio of nano ZnO in earthworms to soil in 250 mg/kg treatment group was lower than that in 10 mg/kg treatment group as the earthworms would not take up too much nano ZnO to protect themselves from the damage. Combination of in-vivo and in-vitro tests was adapted to investigate the toxic mechanism of nano ZnO to earthworms. In in-vivo test, biomarkers including ROS, SOD, and MDA suggested that the toxic effects of nano ZnO to earthworms were caused by the oxidative stress. To further elucidate its toxic mechanism, in-vitro toxicity test was carried out by employing earthworm coelomocytes. The biomarkers, intracellular ROS, extracellular LDH, and cell viability showed concentration-dependent manner with nano ZnO in the culture media, demonstrating that in-vitro toxicity test could be utilized to reveal the toxic mechanism of nano ZnO to earthworms or other organisms.

High-performance porous biochar from the pyrolysis of natural and renewable seaweed (Gelidiella acerosa) and its application for the adsorption of methylene blue

A high-performance porous biochar adsorbent prepared by facile thermal pyrolysis of seaweed (Gelidiella acerosa) is reported. The textural characteristics of the prepared seaweed biochar (SWBC) and the performance in the adsorption of methylene blue (MB) dye were evaluated. The batch experiment for the adsorption of MB was conducted under different parameters, such as temperature, pH, and initial concentration of MB in the range of 25-400 mg/L. The developed SWBC exhibited a relatively high surface area, average pore size, and pore volume of 926.39 m²/g, 2.45 nm, and 0.57 cm³/g, respectively. The high surface area and pristine mineral constituents of the biochar promoted a high adsorption capacity of 512.67 mg/g of MB at 30 °C. The adsorption isotherm and kinetics data best fitted the Langmuir and pseudo-second-order equations. The results indicate that SWBC is efficient for MB adsorption and could be a potential adsorbent for wastewater treatment.

Environmental risks of ZnO nanoparticle exposure on Microcystis aeruginosa: Toxic effects and environmental feedback

The vast majority of studies measure the toxic effect of organisms exposed to nanoparticles (NPs) while there is still a lack of knowledge about the influence of NPs on the aquatic environment. It is unknown whether or not the interaction between NPs and algae will result in the variation of algal organic matter (AOM) and stimulate the production of more algal toxins. In this study, zinc oxide nanoparticles (nano-ZnO) as a typical representative of metal oxide NPs were used to evaluate the toxic effects and environmental feedback of Microcystis aeruginosa. Reactive oxygen species (ROS) and malondialdehyde (MDA) were measured to explain the toxicity mechanism. Changes of AOM, including the production of toxins, the molecular weight distribution and the excitation-emission matrices of algal solution were also studied as environmental feedback indicators after nano-ZnO destroyed the algae. As the nano-ZnO exceeded the comparable critical concentration (1.0 mg/L), the algae were destroyed and intracellular organic matters were released into the aquatic environment, which stimulated the generation of microcystin-LR (MC-LR). However, it is worth noting that the concentration of nano-ZnO would need to be high (at mg/L range) to stimulate more MC-LR production. These findings are expected to be beneficial in interpreting the toxicity and risks of the releasing of NPs through the feedback between algae and the aquatic environment.

Biosynthesis of Inorganic Nanoparticles: A Fresh Look at the Control of Shape, Size and Composition

Several methodologies have been devised for the design of nanomaterials. The "Holy Grail" for materials scientists is the cost-effective, eco-friendly synthesis of nanomaterials with controlled sizes, shapes and compositions, as these features confer to the as-produced nanocrystals unique properties making them appropriate candidates for valuable bio-applications. The present review summarizes published data regarding the production of nanomaterials with special features via sustainable methodologies based on the utilization of natural bioresources. The richness of the latter, the diversity of the routes adopted and the tuned experimental parameters have led to the fabrication of nanomaterials belonging to different chemical families with appropriate compositions and displaying interesting sizes and shapes. It is expected that these outstanding findings will encourage researchers and attract newcomers to continue and extend the exploration of possibilities offered by nature and the design of innovative and safer methodologies towards the synthesis of unique nanomaterials, possessing desired features and exhibiting valuable properties that can be exploited in a profusion of fields.