Green Synthesis of Silver Oxide Nanoparticles for Photocatalytic Environmental Remediation and Biomedical Applications

Multifunctional Ag2O/chitosan nanocomposites synthesized via sol-gel with enhanced antimicrobial, and antioxidant properties: A novel food packaging material

In this study, a single step in situ sol-gel method was used to syntheses nanocomposite films using chitosan (CS) as the basis material, with the addition of silver oxide nanoparticles (Ag2O) at several weight percentages (5 %, 10 %, and 15 % Ag2O/CS). The structural characteristics of Ag2O/CS films were investigated using a range of analytical techniques. The presence of the primary distinctive peaks of chitosan was verified using FTIR spectra analysis. However, a minor displacement was observed in these peaks due to the chemical interaction occurring with silver oxide molecules. XRD analysis demonstrated a significant increase in the crystallinity of chitosan when it interacted with metal oxide nanoparticles. Furthermore, it is believed that the interaction between silver oxide and the active binding sites of chitosan is responsible for the evenly dispersed clusters shown in the micrographs of the chitosan surface, as well as the random aggregations within the pores. EDS technique successfully identified the presence of distinctive silver signals within the nanocomposite material, indicating the successful absorption of silver into the surface of the polymer. The developed Ag2O/CS nanocomposite showed promising antibacterial activity against Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive bacteria (Bacillus subtilis, Enterococcus faecalis and Staphylococcus aureus). Also, Ag2O/CS nanocomposite exhibited marked antifungal activity against Candida albicans, Aspergillus flavus, A. fumigatus, A. niger, and Penicillium chrysogenum. The antioxidant activity of the developed nanocomposite films was studied by ABTS radical scavenging. The highest antioxidant and antibacterial properties were achieved by including 15 % silver oxide into the chitosan. Therefore, our finding indicate that chitosan‑silver oxide nanocomposites exhibits significant potential as a viable material for application in several sectors of the food packaging industry.

Biosynthesis of Bt-Ag2O nanoparticles using Bacillus thuringiensis and their pesticidal and antimicrobial activities

Nanosilver oxide exhibits strong antibacterial and photocatalytic properties and has shown great application potential in food packaging, biochemical fields, and other fields involving diseases and pest control. In this study, Ag2O nanoparticles were synthesized using Bacillus thuringiensis (Bt-Ag2O NPs). The physicochemical characteristics of the Bt-Ag2O NPs were analyzed by UV‒vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), inductively coupled plasma emission spectrometry (ICP), high-resolution transmission electron microscopy (HR-TEM), and zeta potential. The phis-chemical characterization revealed that the Bt-Ag2O NPs are in spherical shape with the small particle size (18.24 nm), high crystallinity, well dispersity, and stability. The biopesticidal and antifungal effects of Bt-Ag2O NPs were tested against Tribolium castaneum, Aspergillus flavus, and Penicillium chrysogenum. The survival, growth, and reproduction of tested pests and molds were significantly inhibited by Bt-Ag2O NPs in a dose-dependent manner. Bt-Ag2O NPs showed higher pesticidal activities against T. castaneum than Bt and commercial Ag2O NPs. The LC50 values of Bt, Ag2O NPs, and Bt-Ag2O NPs were 0.139%, 0.072%, and 0.06% on day 14, respectively. The Bt-Ag2O NPs also showed well antifungal activities against A. flavus and P. chrysogenum, while it resulted a small inhibition zone than commercial Ag2O NPs did. In addition, A. flavus showed much more sensitive to Bt-Ag2O NP treatments, compared to P. chrysogenum. Our results revealed that Bt-Ag2O NPs synthesized using B. thuringiensis could act as pesticides and antifungal agents in stored-product fields. KEY POINTS: • Bt-Ag2O NPs could be synthesized using Bacillus thuringiensis (Bt). • The NPs showed a high degree of crystallinity, spherical shape, and small particle size. • The NPs also showed excellent insecticidal and antifungal activity.

Wild-Grown Romanian Helleborus purpurascens Approach to Novel Chitosan Phyto-Nanocarriers-Metabolite Profile and Antioxidant Properties

The current nanomedicinal approach combines medicinal plants and nanotechnology to create new scaffolds with enhanced bioavailability, biodistribution and controlled release. In an innovative approach to herb encapsulation in nanosized chitosan matrices, wild-grown Romanian Helleborus purpurascens was used to prepare two new chitosan nanocarriers. The first carrier preparation involved the nanoencapsulation of hellebore in chitosan. The second carrier emerged from two distinct stages: hellebore-AgNPs phyto-carrier system succeeded by nanoencapsulation in chitosan. The morphostructural characteristics and thermal behavior of these newly prepared nanocarriers were examined using FT-IR, XRD, DLS, SEM, EDS and thermogravimetric analyses. In addition, the encapsulation yield, encapsulation efficiency and encapsulation contents were investigated. The antioxidant activity was estimated using four in vitro, noncompetitive methods: total phenolic assay; 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay; phosphomolybdate (i.e., total antioxidant capacity); and iron(III)-phenanthroline antioxidant assay. Moreover, this study reports the first low-molecular-weight metabolite profile of wild-grown Romanian Helleborus purpurascens Waldst. & Kit. A total of one hundred and five secondary metabolites were identified in the mass spectra (MS)-positive mode from fourteen secondary metabolite categories (alkaloids, butenolides, bufadienolides, phytoecdysteroids, amino acids and peptides, terpenoids, fatty acids, flavonoids, phenolic acids, sterols, glycosides, carbohydrates, nucleosides and miscellaneous). The collective results suggest the potential application is a promising new antioxidant vehicle candidate in tumor therapeutic strategy.

Bio-fabricated bismuth-based materials for removal of emerging environmental contaminants from wastewater

Although rapid industrialization has made life easier for humans, several associated issues are emerging and harming the environment. Wastewater is regarded as one of the key problems of the 21st century due to its massive production every year and requires immediate attention from all stakeholders to protect the environment. Since the introduction of nanotechnology, bismuth-based nanomaterials have been used in variety of applications. Various techniques, such as hydrothermal, solvo-thermal and biosynthesis, have been reported for synthesizing these materials, etc. Among these, biosynthesis is eco-friendly, cost-effective, and less toxic than conventional chemical methods. The prime focuses of this review are to elaborate biosynthesis of bismuth-based nanomaterials via bio-synthetic agents such as plant, bacteria and fungi and their application in wastewater treatment as anti-pathogen/photocatalyst for pollutant degradation. Besides this, future perspectives have been presented for the upcoming research in this field, along with concluding remarks.

Eucalyptus globulus Mediated Green Synthesis of Environmentally Benign Metal Based Nanostructures: A Review

The progress in nanotechnology has effectively tackled and overcome numerous global issues, including climate change, environmental contamination, and various lethal diseases. The nanostructures being a vital part of nanotechnology have been synthesized employing different physicochemical methods. However, these methods are expensive, polluting, eco-unfriendly, and produce toxic byproducts. Green chemistry having exceptional attributes, such as cost-effectiveness, non-toxicity, higher stability, environment friendliness, ability to control size and shape, and superior performance, has emerged as a promising alternative to address the drawbacks of conventional approaches. Plant extracts are recognized as the best option for the biosynthesis of nanoparticles due to adherence to the environmentally benign route and sustainability agenda 2030 of the United Nations. In recent decades, phytosynthesized nanoparticles have gained much attention for different scientific applications. Eucalyptus globulus (blue gum) is an evergreen plant belonging to the family Myrtaceae, which is the targeted point of this review article. Herein, we mainly focus on the fabrication of nanoparticles, such as zinc oxide, copper oxide, iron oxide, lanthanum oxide, titanium dioxide, magnesium oxide, lead oxide, nickel oxide, gold, silver, and zirconium oxide, by utilizing Eucalyptus globulus extract and its essential oils. This review article aims to provide an overview of the synthesis, characterization results, and biomedical applications of nanoparticles synthesized using Eucalyptus globulus. The present study will be a better contribution to the readers and the students of environmental research.

Field emission scanning electron microscopic, X-ray diffraction and ultraviolet spectroscopic analysis of Terminalia bellerica based silver nanoparticles and evaluation of their antioxidant, catalytic and antibacterial activity

In recent years, scientists have come up with ways to make nanoparticles that are inexpensive and good for the environment. Terminalia bellerica-based silver nanoparticles (TBAgNPs) were made in this study using methanol extract from T. bellerica fruits. This method was quick, economical, and good for the environment. The biosynthesized TBAgNPs were used as antioxidants, antibacterial agents, and anti-catalytic agents. Analytical techniques like XRD, FESEM, and UV-Vis were used to find out more about the spherical TBAgNPs that were made. Also, Cefotaxime-resistant bacteria found in hospitals were used to test how well the TBAgNPs killed bacteria. With the Bauer-agar Kirby's gel diffusion and Mueller-Hinton broth methods, the ability of the synthesized TBAgNPs to stop bacterial growth was tested. After the TBAgNPs were studied, it was found that the average size of their crystals was between 10 and 25 nm. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) reducing tests showed that these AgNPs could act as antioxidants, and TBAgNPs (%inhibition = 20.90% to 94.94%) were better antioxidant than ascorbic acid (%inhibition = 13.80% to 86.10%) and extract (%inhibition = 16.90% to 80.50%). The reduction of methylene blue (MB) to leucomethylene blue (LMB) with sodium borohydride (NaBH₄) was used as a model to test the catalytic potential of TBAgNPs. On UV spectroscopic analysis at room temperature, TBAgNPs at different concentrations were able to reduce methylene blue effectively. For Escherichia coli and Klebsiella pneumoniae, the minimum inhibitory concentration (MIC) for TBAgNPs was 0.625 μg/mL and 1.25 μg/mL, respectively. Based on these results, silver nanoparticles made with Terminalia bellerica extract may have much biological importance and could be used in making useful therapeutic applications.

A review on the green synthesis of nanoparticles, their biological applications, and photocatalytic efficiency against environmental toxins

Green synthesis of nanoparticles (NPs) using plant materials and microorganisms has evolved as a sustainable alternative to conventional techniques that rely on toxic chemicals. Recently, green-synthesized eco-friendly NPs have attracted interest for their potential use in various biological applications. Several studies have demonstrated that green-synthesized NPs are beneficial in multiple medicinal applications, including cancer treatment, targeted drug delivery, and wound healing. Additionally, due to their photodegradation activity, green-synthesized NPs are a promising tool in environmental remediation. Photodegradation is a process that uses light and a photocatalyst to turn a pollutant into a harmless product. Green NPs have been found efficient in degrading pollutants such as dyes, herbicides, and heavy metals. The use of microbes and flora in green synthesis technology for nanoparticle synthesis is biologically safe, cost-effective, and eco-friendly. Plants and microbes can now use and accumulate inorganic metallic ions in the environment. Various NPs have been synthesized via the bio-reduction of biological entities or their extracts. There are several biological and environmental uses for biologically synthesized metallic NPs, such as photocatalysis, adsorption, and water purification. Since the last decade, the green synthesis of NPs has gained significant interest in the scientific community. Therefore, there is a need for a review that serves as a one-stop resource that points to relevant and recent studies on the green synthesis of NPs and their biological and photocatalytic efficiency. This review focuses on the green fabrication of NPs utilizing diverse biological systems and their applications in biological and photodegradation processes.

Biogenic Synthesis of Multifunctional Silver Oxide Nanoparticles (Ag2ONPs) Using Parieteria alsinaefolia Delile Aqueous Extract and Assessment of Their Diverse Biological Applications

Green nanotechnology has made the synthesis of nanoparticles a possible approach. Nanotechnology has a significant impact on several scientific domains and has diverse applications in different commercial areas. The current study aimed to develop a novel and green approach for the biosynthesis of silver oxide nanoparticles (Ag₂ONPs) utilizing Parieteria alsinaefolia leaves extract as a reducing, stabilizing and capping agent. The change in color of the reaction mixture from light brown to reddish black determines the synthesis of Ag₂ONPs. Further, different techniques were used to confirm the synthesis of Ag₂ONPs, including UV-Visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), Energy-dispersive X-ray spectroscopy (EDX), zeta potential and dynamic light scattering (DLS) analyses. The Scherrer equation determined a mean crystallite size of ~22.23 nm for Ag₂ONPs. Additionally, different in vitro biological activities have been investigated and determined significant therapeutic potentials. Radical scavenging DPPH assay (79.4%), reducing power assay (62.68 ± 1.77%) and total antioxidant capacity (87.5 ± 4.8%) were evaluated to assess the antioxidative potential of Ag₂ONPs. The disc diffusion method was adopted to evaluate the antibacterial and antifungal potentials of Ag₂ONPs using different concentrations (125-1000 μg/mL). Moreover, the brine shrimp cytotoxicity assay was investigated and the LC₅₀ value was calculated as 2.21 μg/mL. The biocompatibility assay using red blood cells (<200 μg/mL) confirmed the biosafe and biocompatible nature of Ag₂ONPs. Alpha-amylase inhibition assay was performed and reported 66% inhibition. In conclusion, currently synthesized Ag₂ONPs have exhibited strong biological potential and proved as an attractive eco-friendly candidate. In the future, this preliminary research work will be a helpful source and will open new avenues in diverse fields, including the pharmaceutical, biomedical and pharmacological sectors.

Waste to catalyst: Role of agricultural waste in water and wastewater treatment

Presently, owing to the rapid development of industrialization and urbanization activities, a huge quantity of wastewater is generated that contain toxic chemical and heavy metals, imposing higher environmental jeopardies and affecting the life of living well-being and the economy of the counties, if not treated appropriately. Subsequently, the advancement in sustainable cost-effective wastewater treatment technology has attracted more attention from policymakers, legislators, and scientific communities. Therefore, the current review intends to highlight the recent development and applications of biochars and/or green nanoparticles (NPs) produced from agricultural waste via green routes in removing the refractory pollutants from water and wastewater. This review also highlights the contemporary application and mechanism of biochar-supported advanced oxidation processes (AOPs) for the removal of organic pollutants in water and wastewater. Although, the fabrication and application of agriculture waste-derived biochar and NPs are considered a greener approach, nevertheless, before scaling up production and application, its toxicological and life-cycle challenges must be taken into account. Furthermore, future efforts should be carried out towards process engineering to enhance the performance of green catalysts to improve the economy of the process.

Green Synthesis of Silver Oxide Microparticles Using Green Tea Leaves Extract for an Efficient Removal of Malachite Green from Water: Synergistic Effect of Persulfate

The removal of water pollutants by photocatalysis is a promising technique, mainly due to its environmentally friendly and sustainable nature. In this study, the degradation of a recalcitrant organic pollutant, malachite green (MG), was investigated in water by a microstructured silver oxide photocatalyst. The silver oxide (Ag2O) microparticles (MPs) were synthesized by a low-cost, green method, mediated by green tea leaves extract. The surface, morphological and optical properties of the synthesized Ag2O MPs were determined by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy, and ultraviolet-visible (UV-visible) spectrophotometry. The synthesized Ag2O MPs showed good photoactivity, represented by 83% degradation of malachite green (MG) ([C]0 = 0.4 mM, Ag2O loading = 0.1 g L−1) at neutral pH, in 3 h. Persulfate ions (PS) showed a strong synergistic effect on the efficiency of solar/Ag2O photocatalysis, represented by complete MG removal in 15 min, in the presence of 1.6 mM PS. The results revealed that solar/Ag2O, particularly solar/Ag2O/PS photocatalysis is a promising method for the elimination of toxic organic pollutants, such as malachite green, from the water environment.

Development of Iron Nanoparticles (FeNPs) Using Biomass of Enterobacter: Its Characterization, Antimicrobial, Anti-Alzheimer's, and Enzyme Inhibition Potential

Nanotechnology is a new field that has gained considerable importance due to its potential uses in the field of biosciences, medicine, engineering, etc. In the present study, bio-inspired metallic iron nanoparticles (FeNPs) were prepared using biomass of Enterobacter train G52. The prepared particles were characterized by UV-spectroscopy, TGA, XRD, SEM, EDX, and FTIR techniques. The crystalline nature of the prepared FeNPs was confirmed by XRD. The SEM techniques revealed the particles size to be 23 nm, whereas in FTIR spectra the peaks in the functional group region indicated the involvement of bioactive compounds of selected bacterial strains in the capping of FeNPs. The EDX confirmed the presence of iron in the engineered FeNPs. The FeNPs were then evaluated for its antibacterial, antifungal, antioxidant, anti-inflammatory, anti-Alzheimer's, anti-larvicidal, protein kinase inhibition, anti-diabetic, and biocompatibility potentials using standard protocols. Substantial activities were observed in almost all biological assays used. The antioxidant, anti-cholinesterase, and anti-diabetic potential of the prepared nanoparticles were high in comparison to other areas of biological potential, indicating that the FeNPs are capable of targeting meditators of oxidative stress leading to diabetes and Alzheimer's disease. However, the claim made needs some further experimentation to confirm the observed potential in in vivo animal models.

Activated Carbon-Loaded Titanium Dioxide Nanoparticles and Their Photocatalytic and Antibacterial Investigations

Activated carbon doping TiO2 nanoparticles were synthesised by zapota leaf extract using the co-precipitation method. The bio-constituents of plant compounds were used in the reactions of stabilization and reductions. The carbon loading on the TiO2 nanoparticles was characterised by XRD, FTIR, UV-DRS, SEM with EDX, and TEM analysis. The loading of activated carbon onto the TiO2 nanoparticles decreased the crystallite size and optical bandgap, and their doping improved the surface structure of AC/TiO2 nanoparticles. Mesoporous/microporous instability was remodified from the activated carbon, which was visualised using SEM and TEM analysis, respectively. The photocatalytic dye degradation of Rh-B dye was degraded in TiO2 and AC/TiO2 nanoparticles under visible light irradiation. The degradation efficiencies of TiO2 and AC/TiO2 nanoparticles were 73% and 91%, respectively. The bacterial abilities of TiO2 and AC/TiO2 nanoparticles were examined by E. coli and S. aureus. The water reclamation efficiency and bactericidal effect of TiO2 and AC/TiO2 nanoparticles were examined via catalytic dye degradation and bacterial efficiency of activated carbon-doped titanium dioxide nanoparticles.

Surface-Oxidized Polymer-Stabilized Silver Nanoparticles as a Covering Component of Suture Materials

In this work, we obtained silver nanoparticles stabilized with polyvinylpyrrolidone, ranging in size from 70 to 110 nm, which exhibits good crystallinity and anisotropic structure. For the first time, we studied the influence of the molar ratio of silver between silver and peroxide on the oxidation process of the nanoparticles and determined the regularities of this process by analyzing changes in absorption spectra. Our results showed that at molar ratios of Ag:H₂O₂ = 1:1 and 1:5, dependences of changes in the intensity, position and half-width of the absorption band of the plasmon resonance are rectilinear. In vivo studies of silver nanoparticles have shown that silver nanoparticles belong to the toxicity class III (moderately hazardous substance) and to the third group according to the degree of accumulation. We established that silver nanoparticles and oxidized silver nanoparticles form a uniform layer on the surface of the suture material. We found that the use of the suture material with silver nanoparticles and oxidized silver nanoparticles does not cause allergic reactions in the organisms of laboratory animals.

Machine Learning Methods and Sustainable Development: Metal Oxides and Multilayer Metal Oxides

The development of nanotechnologies and new methods of machine learning are responsible for the significant attention and demand for metal oxides and multilayer metal-oxide nanostructures [...]