High Electroconductivity Research Articles

High-performance ionic liquid-based membranes employed for efficient recovery of lithium

The effective Li separation in high Na/Li (or K/Li) ratio solution is a challenging issue for Li recovery industry. Here we present a novel functionalized ionic liquid (IL) with high Li selectivity and electroconductivity. This IL is synthesized with the deprotonated thenoyltrifluoroacetone ([TTA]−) anion and methyltributylammonium ([N4441]+) cation. The Li extraction performance and selectivity of [N4441][TTA], as well as extraction mechanism were systematically investigated. Then the [N4441][TTA] is integrated into cellulose triacetate (CTA). An ionic-liquid-based membrane named NTC is produced consisting of 36.1 wt% [N4441][TTA]. The NTC membrane shows a high Li initial flux of 1.89 × 10-2 mol⋅m−2⋅h−1. At a mass ratio Li: Na: K of 1:1:1, the separation factor of Li over the Na and K are 28.86 and 38.26, respectively. Finally, electrodialysis is employed to further enhance the Li transport. The initial flux significantly increases to 2.34 × 10-2 mol⋅m−2⋅h−1 when the current density is 1.5 mA⋅cm−2. This membrane is expected to be used for Li extraction from Na- and K-rich brine solutions.

Laurencia nipponica: New insight on the dependence-factors of element accumulation in iron-enriched seaweed from Mashike, Hokkaido

The present study aims to provide novel information on elemental correlation in specific macroalgae species. We evaluated the accumulation pattern of various elements (Fe, Al, As, Ba, Cd, Cu, Cr, Co, Mn, and Zn) in Laurencia nipponica (Yamada), collected at different distances from the shoreline on the Betsukari coastline. Fe and Al accumulation patterns in L. nipponica were unique and were found to affect the accumulation of other trace elements. Our findings suggest that Fe and Al accumulation is linearly related to the accumulation of essential elements in L. nipponica. Using a Pearson’s correlation and Principal Component Analysis, a relationship was identified between environmental conditions (low total organic carbon and turbidity, but high chlorophyll and electroconductivity) and an increase in the accumulation of essential elements in L. nipponica and a reduction in the accumulation of non-biological or toxic elements. Hence, element accumulation may be dependent on environmental conditions. This study highlights the potential of L. nipponica as a biomarker to identify metal accumulation in the Fe-enriched artificial reef of the Mashike shoreline. This first report elucidates the correlation between inter-species elements and provides valuable insight into the using L. nipponica as an elemental biomarker in Fe-enriched artificial reefs.

Biomimetic and electrostatic self-assembled nanocellulose/MXene films constructed with sequential bridging strategy for flexible supercapacitor

Despite the two-dimensional titanium carbide MXene (Ti3C2Tx) has shown promising applications in energy storage, the inherent self-stacking and weak connectivity among nanosheets present a challenge in manufacturing robust MXene films for emerging flexible supercapacitors. Herein, inspired by the robust “soft-hard” structured exoskeletons of crustaceans, the biomimetic cellulose nanofibers (CNFs)/MXene-Al (CM-Al) film with integrated high mechanical toughness, electroconductivity and electrochemical behavior, sequential bridging with hydrogen and ionic bonds, is crafted via the facile electrostatic self-assembly strategy. The embedded CNFs guide the in-plane orientation of MXene through hydrogen bonding, forming a “soft-hard” microstructure and dramatically enhancing the mechanical toughness of CM-Al. The rigid ionic bonds established between the oxygen-containing groups on CNFs and MXene with Al3+ further elevate the mechanical strength (163.88 MPa) and act as additional electron transfer channels to impart the reinforced electroconductivity (82.63 S cm−1). Benefiting from the more active site exposure induced by the expanded MXene layer spacing after CNFs embedding and the weakened intrinsic resistance caused by the constructed ionic bonding, the assembled flexible quasi-solid-state symmetric supercapacitor with CM-Al as electrode delivers a high area capacitance (679 mF cm−2), energy density (16.2 μWh cm−2), cycling capability (85.3 % capacitance retention after 10,000 cycles) and intrinsic tolerance to various non-stretching deformations. Moreover, the selective principles for metal ions are summarized that involved a comprehensive consideration of ionic radius, charge density and basic chemical properties. This work demonstrates an accessible and feasible construction strategy for flexible composite films and provides an alternative pathway for wearable energy storage devices.

Investigation of electrochemical characteristics of intergel systems based on polyacrylic acid

Currently, hydrogels are polymer materials in high demand due to their physicochemical properties, and recent years have seen significant attention given to the study of their physicochemical properties [1,2]. The purpose of this research is to investigate the effect of remote interaction on the electrochemical properties of intergel systems containing hydrogels of polyacrylic acid, poly-4-vinylpyridine, poly-2-methyl-5-vinylpyridine, and polyethyleneimine hydrogels with various initial states. The dependency of conductivity and pH levels in aqueous solutions of intergel systems was examined. The obtained results have shown thatin the 5:1 ratio of the PAAswollen:P4VPdry intergel system, the conductivity of the aqueous medium reaches its maximum value after 24 hours, with a corresponding decrease in pH level. For the PAAdry:P2M5VPdry hydrogels at ratios of 5:1, 1:5, and 2:4, the high electroconductivity was observed at the sixth hour. The maximum pH value was achieved at a ratio of 4:2, indicating a low presence of nitrogen heteroatoms in the aqueous solution. The maximum conductivity in the PAAswollen:PEIswollen system at a 3:3 ratio was reached after 8.5 hours, while the pH showed its minimum value. In the study of the PAAdry:PEIdry intergel system, the pH of the aqueous medium decreased over time in all hydrogel ratios. An exception was noted at a 4:2 ratio, where pH slightly increased after 0.5 hours, then fell again, showing a deviation from the general pH trend. Conclusion. The conducted research has shown that specific conductivity varies across all molar ratios of hydrogels. It was established that changes in pairs and states of hydrogels in the intergel system affect specific conductivity, indicating the ratio of ionized and dissociated groups in the chain changes normally. These results demonstrate that these intergel systems can be used to get high-selectivity sorbents.

ELECTRICAL STIMULATION COMBINED WITH ADDITIVE MANUFACTURED 3D CONDUCTIVE SCAFFOLDS TOWARDS IMPROVED BONE-TISSUE ENGINEERING STRATEGIES

The growing number of non-union fractures in an aging population has increased the clinical demand for tissue-engineered bone. Electrical stimulation (ES) has been described as a promising strategy for bone regeneration treatments in several clinical studies. However the underlying mechanism by which ES augments bone formation is still poorly understood and its use in bone tissue engineering (BTE) strategies is currently underexplored. Additive manufacturing (AM) technologies (Fused Deposition Modeling/3D Printing) have been widely used in BTE due to their ability to fabricate scaffolds with a high control over their structural and mechanical properties in a reproducible and scalable manner. Thus, in this work, we combined AM methods with conductive biomaterials and ES to enhance the osteogenic differentiation of human bone marrow-derived mesenchymal stem/stromal cells (hBMSCs) envisaging improved BTE strategies.First, we started by developing AM-based electro-bioreactor devices containing medical-grade electrodes (stainless steel and Ti6Al4V) to apply ES to monolayer 2D cultures and 3D cell-seeded scaffolds. Computer modeling(Finite Element Analysis-FEA) was employed to predict the magnitude/distribution of electrical fields within the ES devices and along the different conductive scaffolds. Prior to scaffold culture, 5 different ES protocols were tested in terms of their ability to promote hBMSCs proliferation and osteogenic differentiation in 2D cultures. The best performance ES protocol was then used in two different AM-based BTE strategies: 1) Two different conductive scaffolds (conductive poly lactic acid (PLA) and titanium) were seeded with hBMSCs and cultured for 21 days under osteogenic medium conditions with and without ES and their biological performance was evaluated in comparison to non-conductive standard PLA scaffolds; 2) Different PEDOT:PSS-based coating solutions were screened to obtain PEDOT:PSS/Gelatin-coated 3D polycaprolactone (PCL) scaffolds with a high(11 S.cm-1) and stable electroconductivity. When cultured under ES, PEDOT:PSS/Gelatin-PCL scaffolds enhanced significantly hBMSCs osteogenic differentiation and mineralization(calcium deposition), highlighting their potential for BTE applications.Acknowledgements: Funding received from FCT through projects InSilico4OCReg (PTDC/EME-SIS/0838/2021), OptiBioScaffold (PTDC/EME-SIS/4446/2020) and BioMaterARISES (EXPL/CTM-CTM/0995/2021), and to the institutions iBB (UIDB/04565/2020), CDRSP (UIDB/04044/2020) and Associate Laboratory i4HB (LA/P/0140/2020).

An Ultra-Thin MXene Film for Multimodal Sensing of Neuroelectrical Signals with Artifacts Removal.

Neuroelectrical signals transmitted onto the skin tend to decay to an extremely weak level, making them highly susceptible to interference from the environment and body movement. Meanwhile, for comprehensively understanding cognitive nerve conduction, multimodal sensing of neural signals, such as magnetic resonance imaging (MRI) and functional near-infrared spectroscopy (fNIRS), is highly required. Previous metal or polymer conductors cannot either provide a seamless on-skin feature for accurate sensing of neuroelectrical signals or be compatible with multimodal imaging techniques without opto- and magnet- artifacts. Herein, a ≈20nm thick MXene film that is able to simultaneously detect electrophysiological signals and perform imaging by MRI and fNIRS with high fidelity is reported. The ultrathin film is made of crosslinked Ti3 C2 Tx film via poly (3,4-ethylene dioxythiophene): polystyrene sulfonate (PEDOT:PSS), showing a record high electroconductivity and transparency combination (11000Scm-1 @89%). Among them, PEDOT: PSS not only plays a cross-linking role to stabilize MXene film but also shortens the interlayer distance for effective charge transfer and high transparency. Thus, it can achieve a low interfacial impedance with skin or neural surfaces for accurate recording of electrophysiological signals with low motion artifacts. Besides, the high transparency originating from the ultrathin feature leads to good compatibility with fNIRS and MRI without optical and magnetic artifacts, enabling multimodal cognitive neural monitoring during prolonged use.

Co/VN heterojunction anchored on multi-dimensional N-doped carbon for high-performance zinc–air batteries

Thanks to high electroconductivity and excellent electrochemical durability, the vanadium nitride (VN) is gradually developed as an electrocatalyst. However, the oxygen dissociation ability of VN species is usually weak due to the lack of d-orbital electrons in the vanadium. Herein, Co nanoparticles with abundant 3d-orbital electrons were utilized to construct the heterojunction with the VN (Co/VN), which anchored on the multi-dimensional N-doped carbon (CoVN/NC) for oxygen reduction reaction (ORR). The heterogeneous interface within the Co/VN increased more active sites and was conducive to adsorbing more O-containing intermediates. The oxygen dissociation ability of intermediates was improved on the VN surface. Based on “3d-orbital electron complementary effect”, the Co nanoparticles transferred d-orbit electrons to the VN and regulated the electronic configuration of VN components. The continuity of the V 3dz2 orbitals within the Co/VN was enhanced near the Fermi level, which promoted the formation of strong σ bonds between the CoVN/NC and O pz orbitals. Therefore, the O–O bond of O2 was more easily broken on the CoVN/NC surface. The CoVN/NC displayed the half-wave potential of 0.85 V for ORR. The zinc-air battery with the CoVN/NC possessed a power density of 200.7 mW cm−2 and a cycle stability of 180 h. This work would provide a practical reference for improving electrocatalytic activities of VN species.

Polymer Electrolytes Based on Polybenzimidazole, Poly(Vinylidene Fluoride-co-Hexafluoropropylene), and Ionic Liquids

Ionic liquids, salts with melting temperature below 100°C, have continuously attracted research interest. Introduction of ionic liquids in a polymer matrix affords polymer electrolytes exhibiting extremely high electroconductivity and electrochemical stability, membranes on their basis possessing good mechanical properties. Diversity of the polymers/copolymers suitable as the matrix as well as practically unlimited variety of ionic liquids (obtained via variation of the anion-cation composition and additional modification of the ions chemical structure) have afforded the polymer electrolytes with a wide range of the physico-chemical properties. In this study, the attention has been primarily focused on the results published over the recent decades and related to investigation of electrolytes for electrochemical devices, in which the membranes based on polybenzimidazole (meta-PBI), the poly(vinylidene fluoride-со-hexafluoropropylene) (PVdF-HFP) copolymer, and ammonium or imidazolium ionic liquids have been used. Various types of polymer electrolytes differing in the composition and the application range have been considered in this study: polymer + ionic liquid, polymer + ionic liquid + acid, and polymer + ionic liquid + lithium/sodium salt. Moreover, the influence of the fillers, introduced in the above-said polymer electrolytes to improve the properties and resolve the issue of the ionic liquid retention in the membrane, has been discussed. This report presents vast data sets (tables) on the electroconductivity and thermal stability of more than 100 polymer electrolytes, which are demanded by the broad journal audience.

Biomimetic patternable polyhydroxyl nanocellulose/MXene films sequentially bridged through a synergistic hydrogen and ionic interaction with tunable multi-photoresponsive performances

High-performance electronics based on transition-metal carbides/nitrides (MXene) have attracted extensive attention due to their two-dimensional structure, modifiable surface chemistry and excellent conductivity. However, because of the weak interconnections between adjacent nanosheets, the construction of robust and flexible macroscopic MXene-based films for wearable electronics remains a challenge. Herein, mechanically tough, highly electroconductive and multi-photoresponsive films (TTM-Al) with a hierarchical nacre-like structure composed of tannic acid-modified 2,2,6,6-tetramethylpiperidin-1-yloxy-oxidized cellulose nanofibers (TA@TOCNs) and MXene are developed via sequentially bridged hydrogen and ionic bonds. TA@TOCNs with abundant phenolic hydroxyl groups as the intercalation layer can enhance the hydrogen bonding interactions with adjacent MXene nanosheets and improve the dispersibility, film-forming ability, mechanical toughness, as well as the in-plane orientation of MXene nanosheets, which can facilitate the construction of well-aligned “brick and mortar” structure. The ionic bonds induced by aluminum ions and oxygen-containing groups in TA@TOCNs and MXene can not only strengthen the interlocking ability and mechanical toughness of TTM-Al, but also promote the electron transfer and heat conduction between MXene nanosheets. Benefiting from the synergism of sequentially bridged hydrogen and ionic bonds, the optimized ultra-thin TTM-Al (∼40 μm) integrates high mechanical strength (∼118.56 MPa), toughness (∼6.84 MJ m−3), electroconductivity (∼5587 S m−1), photoelectric response (photosensitivity ∼ 3050%) and fast photothermal conversion capability (saturation temperature up to 181.6 °C in only 20 s) under near-infrared irradiation. The patternable and flexible devices based on polydimethylsiloxane encapsulated TTM-Al demonstrate the tunable photoelectric/photothermal dual response, enhanced mechanical and waterproof properties, delivering an alternative construction strategy for next-generation multifunctional photoresponsive wearable devices.

Effect of Edge-Chemistry on Graphene-Based Hybrid Electrode Materials for Energy Storage Device

Owing to the rapid climate change, a high-performance energy storage system (ESS) for efficient energy consumption has been receiving considerable attention. ESS, such as capacitors, usually has issues with the ion diffusion of electrode materials, resulting in a decrease in their capacitance. Notably, appropriate pore diameter and large specific surface area (SSA) may result in an effective ion diffusion. Therefore, graphene and multi-walled carbon nanotube (graphene@MWCNT) hybrid nanomaterials, with covalent bonds between the graphene and MWCNT, were prepared via an edge-chemistry reaction. The properties of these materials, such as high porosity, large SSA, and high electroconductivity, make them suitable to be used as electrode materials for capacitors. The optimal ratio of graphene to MWCNT can affect the electrochemical performance of the electrode material based on its physical and electrochemical properties. The supercapacitor using optimal graphene-based hybrid electrode material exhibited highest specific capacitance value as 158 F/g and excellent cycle stability.

Synthesis of functional ionic liquids with high extraction rate and electroconductivity for lithium-magnesium separation and metallic magnesium production from salt lake brine

The effective separation between Li+ and Mg2+ in high Mg/Li ratio brine and the high-efficiency dehydration of MgCl2·6H2O during metallic Mg production are two major challenges of salt lake chemical industry. Herein, a functional ionic liquid with high electroconductivity and extraction rate on Mg2+ was successfully synthesized with methyltrioctylammonium ([A336]+) as the cation and saponified di-(2-ethylhexyl) phosphoric ([P204]−) as the anion. When methyl isobutyl ketone (MIBK) was used as the diluent, the single extraction rate for Mg2+ with a concentration up to 50.42 g·L−1 reached 83.99% at the phase ratio R(O/A) = 10:1, and the electroconductivity of the organic phase after extraction was more than 550 μS·cm−1. The Mg2+ was confirmed to be extracted by coordination interaction to form MgCl2·2[A336][P204], and meanwhile the low intermiscibility of the extraction system with brine was also illustrated by the extraction phase equilibrium. Based on these excellent performances, the extraction system was successfully applied for Mg2+ and Ca2+ purification from lithium-rich brine. In particular, because of the high extraction rate and electroconductivity of the developed system, a novel “extraction-electrodeposition” technology was proposed for metallic Mg production from salt lake brine, by which it successfully avoids the dehydration process of MgCl2·6H2O and the high temperature molting of anhydrous MgCl2 during the traditional production of metallic Mg by electrolysis. The simplicity and low energy consumption properties of the proposed technology provides a new strategy for the effective exploitation of Li and Mg resources in salt lake brine.

Ionic Liquid-Functionalized ZrO2/Reduced Graphene Oxide Nanocomposites for Carcinoembryonic Antigen Electrochemical Detection

Herein, we develop an electrochemical immunosensor based on a zirconia-reduced graphene oxide-1-ethyl-3-methylimidazolium tetrafluoroborate (EMIM.BF4) ionic liquid (ZrO2-rGO-IL) nanocomposite for the detection of a carcinoembryonic antigen (CEA) breast cancer biomarker. The characterization results of the synthesized ZrO2-rGO-IL nanocomposite show that it has high electroconductivity, oxygen functionalities, and a larger active surface area, which favors high loading of anti-CEA antibodies. The fabricated BSA/anti-CEA/ZrO2-rGO-IL/GCE immunosensor can detect CEA with high sensitivity and selectivity in a broad detection range between 25.0 fg mL–1 and 25.0 ng mL–1 with an ultralow limit of detection (LOD) of 1.23 fg mL–1 through differential pulse voltammetry (DPV). In addition, we tested the CEA in serum samples having linear detection ranges from 100.0 fg mL–1 to 5.0 ng mL–1 with an LOD of 2.25 fg mL–1. Subsequently, the incubation time and selectivity of the immunosensor show a great affinity for CEA. Therefore, the proposed immunosensor can be a promising candidate for CEA detection in clinical specimens. Prospectively, the synthesized nanocomposite will have the potential for the effective detection of other cancer biomarkers.

Dynamic Liquid Metal Catalysts for Boosted Lithium Polysulfides Redox Reaction.

Designing efficient electrocatalysts with high electroconductivity, strong chemisorption, and superior catalytical efficiency to realize rapid kinetics of the lithium polysulfides (LiPSs) conversion process is crucial for practical lithium-sulfur (Li-S) battery applications. Unfortunately, most current electrocatalysts cannot maintain long-term stability due to the possible failure of catalytic sites. Herein, a novel dynamic electrocatalytic strategy with the liquid metal (i.e., gallium-tin, EGaSn) to facilitate LiPSs redox reaction is reported. The combined theoretical simulations and microstructure experiment analysis reveal that Sn atoms dynamically distributed in the liquid Ga matrix act as the main active catalytic center. Meanwhile, Ga provides a uniquely dynamic environment to maintain the long-term integrity of the catalytic system. With the participation of EGaSn, a tailor-made 2 Ah Li-S pouch cell with a specific energy density of 307.7Wh kg-1 is realized. This work opens up new opportunities for liquid-phase binary alloys as electrocatalysts for high-specific-energy Li-S batteries.

Fabrication of well-dispersed Pt nanoparticles onto the donor-acceptor type conjugated polymers for high-efficient photocatalytic hydrogen evolution

It is still challenging to fabricate photocatalysts via loaded metal cocatalysts with good dispersion onto the conjugated polymers (CPs). Herein, a donor-acceptor (D–A) structural CP of PyDTDO-3 was employed to host platinum (Pt) nanoparticles (NPs) using N, N′-dimethylformamide (DMF) as a protectant, stabilizer, and reducing agent, which not only promotes Pt NPs to have excellent dispersion property on the surface of PyDTDO-3 but also endows Pt NPs to maintain metallic Pt0 species. As a result, the PyDTDO-3 loaded with Pt NPs exhibits remarkable hydrogen (H2) evolution activity with a rate of 39.9 mmol g−1 h−1 under visible light irradiation, and the fair stability of optimal 7% Pt/PyDTDO-3 is expressed in the rate of H2 generation upon 30 h cycling. Based on density functional theory (DFT) calculations, it has been demonstrated that Pt NPs are selectively loaded onto the acceptor (A) unit of PyDTDO-3 that has the lowest adsorption energies (Eads) and the closest bond lengths between the Pt NPs and PyDTDO-3. Moreover, there are much more electrons filling at the Fermi level (Ef), indicating the optimal 7% Pt/PyDTDO-3 with high electroconductivity timely captured and removed the photoinduced electrons and thus realized the space separation efficiency of electron-hole pairs. Overall, our findings offer a rational way to load metal cocatalysts onto CPs with good dispersion for efficient photocatalytic H2 evolution.

Insights into endophytic bacterial diversity of rice grown across the different agro-ecological regions of West Bengal, India.

Endophytes have recently garnered importance worldwide and multiple studies are being conducted to understand their important role and mechanism of interaction inside plants. But before we indulge in their functions it is necessary to dig into the microbiome. This will help to get a complete picture of the microbes intrinsic to their host and understand changes in community composition with respect to their habitats. To fulfil this requirement in our study we have attempted to dissect the endophytic diversity in roots of rice plant grown across the various agro-ecological zones of West Bengal by undergoing amplicon analysis of their 16S rRNA gene. Based on the measured environmental parameters agro-ecological zones can be divided into two groups: nutrient dense groups, representing zones like Gangetic, Northern hill and Terai-Teesta zone characterised by soil with higher levels of nitrogen (N) and total organic carbon and nutrient low groups representing Coastal saline, Red-laterite and Vindhyan zone mainly characterised by high electroconductivity and pH. Gammaproteobacteria, Alphaproteobacteria, Bacilli and Bacteroidetes were mostly abundant in nutrient dense sites whereas Clostridia and Planctomycetes were concentrated in nutrient low sites. Few genera (Aeromonas, Sulfurospirillum, Uliginosibacterium and Acidaminococcus) are present in samples cultivated in all the zones representing the core microbiome of rice in West Bengal, while some other genera like Lactococcus, Dickeya, Azonexus and Pectobacterium are unique to specific zone. Hence it can be concluded that this study has provided some insight in to the endophytic status of rice grown across the state of West Bengal.

Perspective and prospects of 2D MXenes for smart biosensing

The success of internet-of-things (IoT)-assisted wearable biomedical electronics demands novel high-performance biosensing prototypes which depend on smart opto-electric-nanosystems. In this direction, 2D MXenes (early transition metal carbides/nitrides) have recently emerged as materials of choice to investigate biosensors of desired performance due to high electro-conductivity, hydrophilicity, and versatile surface chemistry. This letter highlights recent advances and current challenges to project MXenes for next generation biosensing based on unfurled potentials and novel bio-analytical technologies.

High AC and DC Electroconductivity of Scalable and Economic Graphite-Diamond Polylactide Nanocomposites.

Two types of graphite/diamond (GD) particles with different ash content was applied to prepare new electroconductive polylactide (PLA)-based nanocomposites. Four samples of nanocomposites for each type of GD particles with mass fraction 0.01, 0.05, 0.10, and 0.15 were prepared via an easily scalable method—melt blending. The samples were subjected to the studies of electrical properties via broadband dielectric spectroscopy. The results indicated up to eight orders of magnitude improvement in the electrical conductivity and electrical permittivity of the most loaded nanocomposites, in reference to the neat PLA. Additionally, the influence of ash content on the electrical conductivity of the nanocomposites revealed that technologically less-demanding fillers, i.e., of higher ash content, were the most beneficial in the light of nanofiller dispersibility and the final properties.

Antioxidant Determination with the Use of Carbon-Based Electrodes

Antioxidants are compounds that prevent or delay the oxidation process, acting at a much smaller concentration, in comparison to that of the preserved substrate. Primary antioxidants act as scavenging or chain breaking antioxidants, delaying initiation or interrupting propagation step. Secondary antioxidants quench singlet oxygen, decompose peroxides in non-radical species, chelate prooxidative metal ions, inhibit oxidative enzymes. Based on antioxidants’ reactivity, four lines of defense have been described: Preventative antioxidants, radical scavengers, repair antioxidants, and antioxidants relying on adaptation mechanisms. Carbon-based electrodes are largely employed in electroanalysis given their special features, that encompass large surface area, high electroconductivity, chemical stability, nanostructuring possibilities, facility of manufacturing at low cost, and easiness of surface modification. Largely employed methods encompass voltammetry, amperometry, biamperometry and potentiometry. Determination of key endogenous and exogenous individual antioxidants, as well as of antioxidant activity and its main contributors relied on unmodified or modified carbon electrodes, whose analytical parameters are detailed. Recent advances based on modifications with carbon-nanotubes or the use of hybrid nanocomposite materials are described. Large effective surface area, increased mass transport, electrocatalytical effects, improved sensitivity, and low detection limits in the nanomolar range were reported, with applications validated in complex media such as foodstuffs and biological samples.

Highly electroconductive lightweight graphene fibers with high current-carrying capacity fabricated via sequential continuous electrothermal annealing

The recent increase in demand for miniaturized electronics has necessitated the development of lightweight, narrow, and flexible channels with high current density as next-generation conductors. Despite the high electrical conductivity and current-carrying capacity (i.e., ampacity) of conventional metal conductors (e.g., copper and gold), their high mass density should be overcome for potential weight-critical applications. In this regard, defect-free graphene fibers (GFs) are excellent alternatives owing to their lightweight and high electroconductivity. In this study, GFs were electrothermally annealed at ~3000 K for a very short time (~50 s) via sequential continuous current injection. This treatment led to the carbonization and subsequent graphitization of the GFs, resulting in successful reparation of the structural disorder and crystalline defects of the GFs. This continuous process is advantageous for scaled production of highly electroconductive GFs. The resultant meter-scale GFs exhibit an electrical conductivity of 2721 S cm−1, maximum ampacity of 3.84 × 104 A cm−2, and specific current-carrying capacity of 4.67 × 104 A cm g−1, which are higher than the corresponding values of a commercial copper wire. This study provides a versatile and cost-effective technique for the development of advanced fibers and films as lightweight conductors for relevant applications.

NiSe2/Ni5P4 nanosheets on nitrogen-doped carbon nano-fibred skeleton for efficient overall water splitting

Combining a variety of factors to optimize the performances of electrocatalysts has become a new breakthrough for the development of low-cost electrolytic catalysts. In this work, we constructed N-doped carbon fibers as the substrate, which could provide high electronic conductivity and large surface area for the load of active catalysts, as well as close incorporation. The nanosheets morphology of NiSe2/Ni5P4 is conducive to enlarging the specific surface area and exposing more active sites. The electrical conductivity is improved by the selenide and carbon nano-fiber substrate. The multiple features, including the unique structure characteristics, heterostructure of NiSe2 and Ni5P4, and high electroconductivity, endow NiSe2/Ni5P4 with superior catalytic activity towards water splitting. As a result, the overpotentials at the cathode current density of 10 and 100 mA cm−2 upon NiSe2/Ni5P4 nanosheets are 112 and 350 mV in 0.5 M H2SO4. For oxygen evolution reaction (OER), the overpotential of NiSe2/Ni5P4 nanosheets at a current density of 10 mA cm−2 in alkaline electrolyte is 316 mV. Furthermore, the bifunctional NiSe2/Ni5P4 nanosheets exhibit excellent working stability for both HER, OER and overall water splitting, showing potential application in hydrogen energy.