Characterization of iron nanoparticles/reduced graphene oxide composites synthesized by one step eucalyptus leaf extract

Comparative toxicology of algal cell extracts and pure cyanotoxins: insights into toxic effects and mechanisms of harmful cyanobacteria Raphidiopsis raciborskii

Ongoing research on cyanotoxins, driven by the socioeconomic impact of harmful algal blooms, emphasizes the critical necessity of elucidating the toxicological profiles of algal cell extracts and pure toxins. This study comprehensively compares Raphidiopsis raciborskii dissolved extract (RDE) and cylindrospermopsin (CYN) based on Daphnia magna assays. Both RDE and CYN target vital organs and disrupt reproduction, development, and digestion, thereby causing acute and chronic toxicity. Disturbances in locomotion, reduced behavioral activity, and weakened swimming capability in D. magna have also been reported for both RDE and CYN, indicating the insufficiency of conventional toxicity evaluation parameters for distinguishing between the toxic effects of algal extracts and pure cyanotoxins. Additionally, chemical profiling revealed the presence of highly active tryptophan-, humic acid-, and fulvic acid-like fluorescence compounds in the RDE, along with the active constituents of CYN, within a 15-day period, demonstrating the chemical complexity and dynamics of the RDE. Transcriptomics was used to further elucidate the distinct molecular mechanisms of RDE and CYN. They act diversely in terms of cytotoxicity, involving oxidative stress and response, protein content, and energy metabolism, and demonstrate distinct modes of action in neurofunctions. In essence, this study underscores the distinct toxicity mechanisms of RDE and CYN and emphasizes the necessity for context- and objective-specific toxicity assessments, advocating nuanced approaches to evaluate the ecological and health implications of cyanotoxins, thereby contributing to the precision of environmental risk assessments.

Green synthesis of nanomaterials by using plant extracts as reducing and capping agents

An alternative method to conventional synthesis is examined in this review by the use of plant extracts as reducing and capping agents. The use of plant extracts represents an economically viable and environmentally friendly alternative to conventional synthesis. In contrast to previous reviews, this review focuses on the synthesis of nano-compounds utilizing plant extracts, which lack comprehensive reports. In order to synthesize diverse nanostructures, researchers have discovered a sustainable and cost-effective method of harnessing functional groups in plant extracts. Each plant extract is discussed in detail, along with its potential applications, demonstrating the remarkable morphological diversity achieved by using these green synthesis approaches. A reduction and capping agent made from plant extracts is aligned with the principles of green chemistry and offers economic advantages as well as paving the way for industrial applications. In this review, it is discussed the significance of using plant extracts to synthesize nano-compounds, emphasizing their potential to shape the future of nanomaterials in a sustainable and ecologically friendly manner.

Synergetic effect of green synthesized reduced graphene oxide and nano-zero valent iron composite for the removal of doxycycline antibiotic from water

In this work, the synthesis of an rGO/nZVI composite was achieved for the first time using a simple and green procedure via Atriplex halimus leaves extract as a reducing and stabilizing agent to uphold the green chemistry principles such as less hazardous chemical synthesis. Several tools have been used to confirm the successful synthesis of the composite such as SEM, EDX, XPS, XRD, FTIR, and zeta potential which indicated the successful fabrication of the composite. The novel composite was compared with pristine nZVI for the removal aptitude of a doxycycline antibiotic with different initial concentrations to study the synergistic effect between rGO and nZVI. The adsorptive removal of bare nZVI was 90% using the removal conditions of 25 mg L^-1, 25 °C, and 0.05 g, whereas the adsorptive removal of doxycycline by the rGO/nZVI composite reached 94.6% confirming the synergistic effect between nZVI and rGO. The adsorption process followed the pseudo-second order and was well-fitted to Freundlich models with a maximum adsorption capacity of 31.61 mg g^-1 at 25 °C and pH 7. A plausible mechanism for the removal of DC was suggested. Besides, the reusability of the rGO/nZVI composite was confirmed by having an efficacy of 60% after six successive cycles of regeneration.

Highly light-tunable memristors in solution-processed 2D materials/metal composites

Memristors—competitive microelectronic elements which bring together the electronic sensing and memory effects—potentially are able to respond against physical and chemical effects that influence their sensing capability and memory behavior. However, this young topic is still under debate and needs further attention to be highly responding to or remaining intact against physical effects, e.g., light illumination. To contribute to this scenario, using a composite of two-dimensional graphene or MoS2 doped with meso-structures of metal/metal-oxides of Ag, Cu and Fe family, we presented scalable and printable memristors. The memristive behavior shows strong dependency upon light illumination with a high record of 105 ON/OFF ratio observed so far in 2-terminal systems based on two-dimensional materials or metal oxide structures. Moreover, we found that the memristors can remain stable without illumination, providing a novel approach to use these composites for developing neuromorphic computing circuits. The sensing and memristive mechanisms are explained based on the electronic properties of the materials. Our introduced materials used in the memristor devices can open new routes to achieve high sensing capability and improve memristance of the future microelectronic elements.

Green Synthesis of Superparamagnetic Iron Oxide Nanoparticles with Eucalyptus globulus Extract and Their Application in the Removal of Heavy Metals from Agricultural Soil

The green synthesis of metal oxide nanoparticles is presented as an excellent sustainable alternative for achieving nanostructures, with potential applications. This research provides important information regarding the influence of the type of solvent used in extracting organic reducing agents from E. globulus on the FeO NPs green synthesis protocol. A broad approach to characterization is presented, where UV-vis spectrophotometry suggests the presence of this type of nanoparticulate material. Likewise, the reduction mechanism was evaluated by FT-IR and the magnetic properties were evaluated by PPSM. In addition, characterizations were linked via elemental analysis (EDX), crystallographic characterization (XRD), electron microscopy (SEM/STEM), and Z potential to evaluate colloidal stability. The results show the influence of the type of solvent used for the extraction of organic reducing agents from E. globulus, and the effect on the synthesis of FeO NPs. In addition, the nanostructure material obtained showed excellent efficiency in the remediation of agricultural soil, eliminating metals such as Cr-VI, Cd, and, to a lesser extent, Pb.

PM2.5 induces intestinal damage by affecting gut microbiota and metabolites of rats fed a high-carbohydrate diet

PM_2.5 has a major impact on the gastrointestinal system, but the specific mechanism behind this action is not fully understood. Current studies have focused on the relationship between PM_2.5 and intestinal flora disorder, while ignoring the important influence of diet on gut microbes. In this study, SD rats were fed either a normal, high-fat, or high-carbohydrate diet for two months and exposed to PM_2.5 (7 mg/kg b.w.) by intratracheal instillation. The results showed that the body and kidney weights of the rats in the high-fat diet group were significantly increased relative to those with a normal diet, and changes in the intestinal microbes and metabolites induced by PM_2.5 were observed. Rats in the high-carbohydrate diet group had a significant response, and the diversity and richness indices of the flora were reduced (p < 0.05); additionally, intestinal Biffidobacterium and Lactobacillus were enriched, while many endogenous metabolites were found. Some amino acids derivatives and long-chain fatty acids were increased (p < 0.05). Both diet structure and PM_2.5 exposure can affect the composition of gut microbiota, and intestinal metabolites may be associated with cell membrane damage when a high-carbohydrate diet interacts with PM_2.5. This study considers multiple dietary factors to further supplement the evidence of intestinal damage via PM_2.5.

Toward a Better Understanding of Metal Nanoparticles, a Novel Strategy from Eucalyptus Plants

Nanotechnology is a promising tool that has opened the doors of improvement to the quality of human's lives through its potential in numerous technological aspects. Green chemistry of nanoscale materials (1-100 nm) is as an effective and sustainable strategy to manufacture homogeneous nanoparticles (NPs) with unique properties, thus making the synthesis of green NPs, especially metal nanoparticles (MNPs), the scientist's core theme. Researchers have tested different organisms to manufacture MNPs and the results of experiments confirmed that plants tend to be the ideal candidate amongst all entities and are suitable to synthesize a wide variety of MNPs. Natural and cultivated Eucalyptus forests are among woody plants used for landscape beautification and as forest products. The present review has been written to reflect the efficacious role of Eucalyptus in the synthesis of MNPs. To better understand this, the route of extracting MNPs from plants, in general, and Eucalyptus, in particular, are discussed. Furthermore, the crucial factors influencing the process of MNP synthesis from Eucalyptus as well as their characterization and recent applications are highlighted. Information gathered in this review is useful to build a basis for new prospective research ideas on how to exploit this woody species in the production of MNPs. Nevertheless, there is a necessity to feed the scientific field with further investigations on wider applications of Eucalyptus-derived MNPs.

Colloidal silver combating pathogenic Pseudomonas aeruginosa and MRSA in chronic rhinosinusitis

The emergence of antibiotic resistant bacteria requires for the development of new antimicrobial compounds one of which colloidal silver (CS) having strong bactericidal properties and being the most promising inorganic nanoparticles for the treatment of bacterial infectious diseases. However, their production can be slow and cumbersome. Here, we used Corymbia maculata aqueous leaf extract as a reducing agent to synthesize CS in a single 15-minute process. CS was physico-chemically characterized for shape, size, zeta potential and stability. The Minimal Inhibitory Concentration (MIC) and Minimum Biofilm Eradication Concentration (MBEC) of CS against planktonic and biofilm forms of methicillin-resistant Staphylococcus aureus (MRSA, n = 5), Pseudomonas aeruginosa (n = 5), Haemophilus influenzae (n = 5) and Streptococcus pneumoniae (n = 3) chronic rhinosinusitis clinical isolates were investigated using the microdilution method and resazurin assay, respectively. The in vitro cytotoxicity on bronchial epithelial cells (Nuli-1) was analyzed by the crystal violet proliferation assay. The safety and efficacy of CS was evaluated in an in vivo infection model in Caenorhabditis elegans. CS was spherical in shape with a diameter of between 11-16 nm (TEM analysis) in dried form and 40 nm (NanoSight) in colloidal form and was stable at room temperature and 4 °C for one year. Average MIC and MBEC values varied between 11 and 44 ppm for MRSA, H. influenzae and S. pneumoniae and between 0.2 and 3 ppm for P. aeruginosa. CS was not toxic to Nuli-1 cells or C. elegans at concentrations of 44 ppm and reduced the Colony Forming Units counts by 96.9 % and 99.6 % in C. elegans for MRSA and P. aeruginosa, respectively. In conclusion, a novel, green synthesis of stable CS is demonstrated with good safety and efficacy profiles, particularly against P. aeruginosa in planktonic and biofilm forms. These CS have potential applications against clinical infections, including in the context of CRS.

Green Synthesis of Metallic Nanoparticles and Their Prospective Biotechnological Applications: an Overview

The green synthesis of nanoparticles (NPs) using living cells is a promising and novelty tool in bionanotechnology. Chemical and physical methods are used to synthesize NPs; however, biological methods are preferred due to its eco-friendly, clean, safe, cost-effective, easy, and effective sources for high productivity and purity. High pressure or temperature is not required for the green synthesis of NPs, and the use of toxic and hazardous substances and the addition of external reducing, stabilizing, or capping agents are avoided. Intra- or extracellular biosynthesis of NPs can be achieved by numerous biological entities including bacteria, fungi, yeast, algae, actinomycetes, and plant extracts. Recently, numerous methods are used to increase the productivity of nanoparticles with variable size, shape, and stability. The different mechanical, optical, magnetic, and chemical properties of NPs have been related to their shape, size, surface charge, and surface area. Detection and characterization of biosynthesized NPs are conducted using different techniques such as UV-vis spectroscopy, FT-IR, TEM, SEM, AFM, DLS, XRD, zeta potential analyses, etc. NPs synthesized by the green approach can be incorporated into different biotechnological fields as antimicrobial, antitumor, and antioxidant agents; as a control for phytopathogens; and as bioremediative factors, and they are also used in the food and textile industries, in smart agriculture, and in wastewater treatment. This review will address biological entities that can be used for the green synthesis of NPs and their prospects for biotechnological applications.

Impact of green reduced graphene oxide on sewage sludge bioleaching with Acidithiobacillus ferrooxidanse

Worldwide graphene use is rapidly increasing in a variety of industrial applications to such an extent that efflux into the environment seems inevitable where the likely final reservoirs of graphene wastes is likely to be wastewater treatment plants are. Despite this an understanding of how graphene products impact the bioleaching of metals from sludge is still limited. In this study, the effect of reduced graphene oxide synthesized from eucalyptus leaf extracts (EL-rGO) on Zn²⁺ and Cu²⁺ bioleaching from sludge was investigated. The major new findings were that EL-rGO had a negative effect on Acidithiobacillus ferrooxidans (A. ferrooxidans) growth; since optical density decreased by 0.059 as EL-rGO dose increased from 1 to 50 mg/L, and the bioleaching of Cu²⁺ and Zn²⁺ decreased by 27.7 and 20.2%, respectively. While at a EL-rGO dose of 1 mg/L A. ferrooxidans grew better, scanning electron microscopy (SEM) confirmed that exposure to EL-rGO caused cell membrane disruption at 50 mg/L. Cytotoxicity tests showed that this was related to an increase in lactate dehydrogenase (LDH) release rate and a decrease in superoxide dismutase (SOD) activity. These new findings provide evidence that green synthesized rGO is toxic to microorganisms and that toxicity increased with rGO dose.

Iron oxides/graphene hybrid structures - Preparation, modification, and application as fillers of polymer composites

The current status of knowledge regarding magnetic hybrid structures based on graphene or carbon nanotubes with various forms of iron oxides is reviewed. The paper starts with a summary of the preparation and properties of iron oxide nanoparticles, both untreated and coated with silica or polymer layers. In the next section, organic-inorganic hybrid materials obtained as a result of a combination of graphene or carbon nanotubes and iron chemical compounds are characterized and discussed. These hybrids constitute an increasing percentage of all consumable high performance biomedical, electronic, and energy materials due to their valuable properties and low production costs. The potential of their application as components of materials used in corrosion protection, catalysis, spintronics, biomedicine, photoelectrochemical water splitting and groundwater remediation, as well as magnetic nanoparticles in polymer matrices, are also presented. The last part of this review article is focused on reporting the most recent developments in design and the understanding of the properties of polymer composites reinforced with nanometer-sized iron oxide/graphene and iron oxide/carbon nanotubes hybrid fillers. The discussion presents comparative analysis of the magnetic, electromagnetic shielding, electrical, thermal, and mechanical properties of polymer composites with various iron oxide/graphene structures. It is shown that the introduction of hybrid filler nanoparticles into polymer matrices enhances both the macro- and microproperties of final composites as a result of synergistic effects of individual components and the simultaneous formation of an oriented filler network in the polymer. The reinforcing effect is related to the structure and geometry of hybrid nanoparticles applied as a filler, the interactions between the filler particles, their concentration in a composite, and the method of composite processing.