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•Ternary nanohybrid based on rGO, NiMn2O4, and polyaniline (GNMOP) was fabricated by a three-step green process for supercapacitor applications.•GNMOP exhibited high specific ...capacitance of 757Fg−1 at 1Ag−1 of current density.•GNMOP showed 93% of specific capacitance retention after 2000 cycles.•GNMOP also exhibited high energy density of up to 70Whkg−1 and high power density of up to 12000Wkg−1.
This paper reports a novel porous ternary nanohybrid based on NiMn2O4, reduced graphene oxide, and polyaniline (GNMOP) as a superior supercapacitor electrode material. GNMOP was fabricated using a hydrothermal-assisted thermal annealing method, followed by the conductive wrapping of polyaniline through in-situ polymerization. The structure and morphology of the ternary nanohybrid were characterized by field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). FTIR, XRD, and XPS confirmed the formation of ternary nanohybrid. SEM and Brunauer–Emmett–Teller (BET) measurement revealed the porous nature of GNMOP, whereas HRTEM analysis demonstrated the wrapping of conducting polyaniline (PANI) on binary composite. Such PANI wrapping enhanced the electrochemical performance of the binary nanocomposite. A specific capacitance of 757Fg−1 was achieved for GNMOP at a current density of 1Ag−1, which is much higher than that of the binary nanocomposite and mixed transition metal oxide. In addition, GNMOP exhibited a maximum energy density of 70Whkg−1 and high capacitance retention of ∼93% after 2000 cycles. These outstanding electrochemical performances of GNMOP can be attributed to the proper wrapping of conducting polymer and the synergistic impact of distinct components.
•Multi-functional chitosan/magnesium oxide composite.•High absorptivity and reusable characteristics.•Exhibited a good antibacterial activity.•Highly efficient, biocompatible, eco-friendly and ...low-cost adsorbent.•It can be used as a sustainable material for wastewater treatment.
We report a novel multi-functional magnesium oxide (MgO) immobilized chitosan (CS) composite was prepared by chemical precipitation method. The CS–MgO composite was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy and zeta potential. The composite was applied as a novel adsorbent for removal of methyl orange model dye and the effect of adsorbent dosage, pH and contact time were studied. The adsorption kinetics followed a pseudo second order reaction. The adsorbent efficiency was unaltered even after five cycles of reuse. In addition, the composite exhibited a superior antibacterial efficacy of 93% within 24h against Escherichia coli as measured by colony forming units. Based on the data of present investigation the composite being a biocompatible, eco-friendly and low-cost adsorbent with antibacterial activity could find potential applications in variety of fields and in particular environmental applications.
Ternary ZnCo2O4/reduced graphene oxide/NiO (ZCGNO) nanowire arrays were grown directly on a piece of Ni foam using a simple, facile, cost-effective hydrothermally assisted thermal annealing process ...without the addition of any Ni precursor salt and used as a binder-free supercapacitor electrode. Ni foam was utilized successively as the NiO precursor, binder, and current collector. The resulting 3D ternary composite possessed an ultrahigh specific capacitance of 1256 F/g at a current density of 3 A/g in 6 M KOH solution. Moreover, the three-dimensional electrode exhibited superior electrochemical performance, such as excellent cyclic stability (∼80% capacitance retention after 3000 cycles), maximum energy density of 62.8 Wh/kg, maximum power density of 7492.5 W/kg, and low equivalent series resistance (0.58 Ω). The effects of the electrolyte concentration on the electrochemical performance of ZCGNO were also examined. ZCGNO with this remarkable electrochemical performance may be considered a prospective candidate for high performance supercapacitor applications.
Aflatoxins are carcinogenic secondary metabolites produced by Aspergillus section Flavi that contaminates a wide variety of food and feed products and is responsible for serious health and economic ...consequences. Fermented foods are prepared with a wide variety of substrates over a long fermentation time and are thus vulnerable to contamination by aflatoxin-producing fungi, leading to the production of aflatoxin B1. The mitigation and control of aflatoxin is currently a prime focus for developing safe aflatoxin-free food. This review summarizes the role of major aflatoxin-degrading enzymes such as laccase, peroxidase, and lactonase, and microorganisms in the context of their application in food. A putative mechanism of enzyme-mediated aflatoxin degradation and toxicity evaluation of the degraded products are also extensively discussed to evaluate the safety of degradation processes for food applications. The review also describes aflatoxin-degrading microorganisms isolated from fermented products and investigates their applicability in food as aflatoxin preventing agents. Furthermore, a summary of recent technological advancements in protein engineering, nanozymes, in silico and statistical optimization approaches are explored to improve the industrial applicability of aflatoxin-degrading enzymes.
In this report, zinc oxide nanoparticles (ZnO NPs) decorated reduced graphene oxide (RGO) composite was fabricated by a one-pot approach using supercritical carbon dioxide (scCO2). ScCO2 has gas-like ...diffusivity, extremely low viscosity, and excellent penetration ability, allowing it to debundle RGO nanosheets and disperse ZnO NPs in between. Owing to the near-zero surface tension and excellent wetting ability of scCO2, the NPs are tightly coated on the highly conductive RGO sheets. The electrochemical characteristics of the ZnO/RGO composite were investigated through cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. The composite was capable of delivering a high specific capacitance of 314 F g−1 with excellent cycling stability.
The lack of higher performance energy storage has been widely acknowledged as a major factor hindering further developments in transportation, portable and wearable electronic devices, among other ...key applications. Although supercapacitors (SCs) have been known for more than fifty years, only recently these devices have been considered as promising candidates to fulfil this significant technology gap. Developments in nanotechnology and manufacturing techniques applied to high-performance advanced electrode materials have accelerated progress in this fast-moving field. In this comprehensive overview article, we systematically survey the current state of art on fabrication and the corresponding electrochemical performance of electrode materials for SCs. The text covers novel carbon nanomaterials having different dimensions, such as 0D-carbon quantum dots, 1D-carbon nanostructures (carbon nanotubes, carbon nanofibers, carbon nano yarns and their composites) as well as 2D-carbon materials (graphene, doped-graphene, graphene derivatives and their composites). Emerging fabrication technologies are also addressed, including conventional SCs, as well as asymmetric, flexible, micro, stretchable and wearable devices. Additionally, the drawbacks for each class of electrode material, the major challenges facing the current technologies, and some of the promising research directions in this field have also been discussed.
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•Durable fluorescent N-CDs prepared using C. Retusus via hydrothermal-carbonization.•This method of synthesis and N-CDs is an ideal for sensing of Fe3+ and bio-imaging.•N-CDs was used ...as a promising fluorescent probe for the direct detection of Fe3+.•N-CDs were used as selective probes for yeast C. albicans and C. neoformans.•N-CDs exhibits selective uptake, good biocompatibility and negligible cytotoxicity.
Nitrogen-doped carbon dots (N-CDs) were synthesized from Chionanthus retusus (C. retusus) fruit extract using a simple hydrothermal-carbonization method. Their ability to sense metal ions, and their biological activity in terms of cell viability and bioimaging applications were evaluated. The resulting N-CDs were characterized by various physicochemical techniques such as high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Raman spectroscopy. The optical properties were characterized by ultraviolet visible (UV-vis) fluorescence spectroscopy techniques. The average size of the N-CDs was approximately 5±2nm with an interlayer distance of 0.21nm, as calculated from the HRTEM images. The presence of phytoconstituent functionalities and the percentages of components in the N–CDs were confirmed by XPS studies, and a nitrogen content of 5.3% was detected. The N–CDs demonstrated highly durable fluorescence properties and low cytotoxicity with a quantum yield of 9%. The synthesized N–CDs were then used as probes for the detection of metal ions. The N–CDs exhibited high sensitivity and selectivity towards Fe3+, with a linear relationship between 0 and 2μM and a detection limit of 70μM. The synthesized N–CDs are anticipated to have diverse biomedical applications, particularly for bioimaging, given their high fluorescence, excellent water solubility, good cell permeability, and negligible cytotoxicity. Finally, the potential of N–CDs as biological probes was investigated using fungal (Candida albicans and Cryptococcus neoformans) strains via fluorescent microscopy. We found that N–CDs were suitable candidates for differential staining applications in yeast cells with good cell permeability, localization with negligible cytotoxicity. Hence, N–CDs may find dual utility as probes for the detection of cellular pools of metal ions (Fe3+) and also for early detection of opportunistic yeast infections in biological samples.
A fast and facile microwave approach for the synthesis of fluorescent nitrogen-doped carbon dots (N-CDs) is reported. The N-CDs were hydrothermally synthesized using l-ascorbic acid (AA) and ...β-alanine (BA) as the carbon precursor and the nitrogen dopant, respectively. The morphology of synthesized N-CDs was characterized by high resolution transmission electron microscopy (HR-TEM) and the elemental composition was analyzed using elemental mapping method. The crystallinity and graphitation of N-CDs were examined by X-ray diffraction (XRD) and Raman spectroscopy. The doping of nitrogen over the carbon dots (CDs) was revealed by attenuated total reflection conjunction with Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photo electron spectroscopy (XPS). The optical properties of synthesized N-CDs were examined by UV–Visible (UV–Vis) and fluorescence spectroscopy. The synthesized N-CDs emit strong blue fluorescence at 401nm under excitation of 325nm. The excitation dependent emission property of synthesized N-CDs was exposed from fluorescence results. The quantum yield of synthesized N-CDs is about 14% against the reference quinine sulfate. The cytotoxicity of synthesized N-CDs on Madin-Darby Canine Kidney (MDCK) and HeLa cells were evaluated through Cell Counting Kit-8 (CCK-8) cytotoxicity assay. The results implied that the fluorescent N-CDs showed less cytotoxicity, further which was successfully applied as a staining probe for the confocal imaging of MDCK and HeLa cells.
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•Fluorescent N-CDs were synthesized by simple microwave method.•l-ascorbic acid and β-alanine were used as a carbon and nitrogen source.•Green and inexpensive sources have been used for the synthesis of N-CDs.•N-CDs were applied in bio-imaging of MDCK and HeLa cells.
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•Hierarchical 3D Ni-Co-Mn oxide@Ni foam was synthesized within 30s under microwave.•Max. capacitance was 1151Fg−1 in KOH and increased to 106.5% after 5000 cycles.•Capacitance was ...2356Fg−1 with 79.6% retained after 5000 cycles using K3Fe(CN)6.•Symmetrical supercapacitor was with an ED of 43.8Whkg−1 and PD of 5.8kWkg−1.•Energy density of 41.4Whkg−1 and power density of 5.4kWkg−1 for supercapacitor.
The outstanding performance of nickel foam (NF) as a current collector owing to its better dimensional stability, high electrical conductivity, and less contact resistance has made it a promising candidate for binder-free electrode for supercapacitors. In addition to the current collector, highly stable structures are also favored to facilitate rapid ion insertion and prevent structural collapse of the electrode materials. In this work, a binder-free and controlled structure of Ni-Co-Mn oxide on NF was constructed effectively using microwave irradiation. The structure obtained from the optimal conditions (concentration and holding time) involved hierarchical interconnected nanoflakes with void spaces, forming a stable and conductive network of nanoflakes on the NF. The synergistic effects of three metal (Ni-Co-Mn) oxides resulted in a high specific capacitance of 2536Fg−1 at 5mAcm−2 (6.49Ag−1) in a mixed KOH/K3Fe(CN)6 electrolyte. The as-prepared symmetric device also obtained a high capacitance of 298Fg−1, a high energy density of 41.4Whkg−1, and a high power density of 5.4kWkg−1. The highly architectured Ni-Co-Mn oxide nanoflakes improved the pseudocapacitive performance significantly, making it a promising electrode material for high-performance binder-free supercapacitors.
•This review discusses advancements in the grafting modification of okra polymers.•Various methods for okra polysaccharide extraction are highlighted.•Synthetic strategies for the modification of ...okra polysaccharide are presented.•Applications of okra polysaccharides in different industries are explored.•This review highlights the need for further research on okra polysaccharides.
Okra polysaccharides are biocompatible polymers with antimicrobial, anticancer, hypoglycemic, and antioxidant characteristics and hence are used in different fields such as drug delivery, food industry, and wastewater treatment. Consequently, okra-polymer modification by different methods, such as grafting, to satisfy industrial demands is attracting much scientific attention. Although a large body of literature is available on the extraction of okra polysaccharides and their applications, little is known about their grafting modification. While crosslinking and binary grafting can help in the realization of the desired properties, these methods have not been widely used on okra polysaccharides. In this review, we highlight the different methods used for the extraction of okra polysaccharides and systematically summarize major findings on their grafting modification and applications in different industries. This information will help in designing experimental protocols for the modification of okra polysaccharides to suit future needs.
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