Abstract  Diabetics are susceptible to hepatic dysfunction risks due to hyperglycaemia and insulin therapy. Conventional diabetes treatments improve glycaemic control; however, hepatic hazards associated with these agents remains a challenge. Accordingly, this study sought to investigate the effect of a dioxidovanadium complex (V) on the hepatic function in streptozotocin-induced diabetic rats. Sprague-Dawley rats (240-250 g) were divided into 4 groups (n = 6): nondiabetic control, diabetic control, insulin-treated, and vanadium complex groups. The dioxidovanadium (10, 20, and 40 mg/kg) was administered twice every 2nd day for 5 weeks and blood glucose concentration was monitored weekly. At the end of the experimental period, all the experimental groups were sacrificed, and then the lipid profile, liver superoxide dismutase, glutathione peroxidase and malondialdehyde, plasma alanine aminotransferase and aspartate aminotransferase, and C-reactive protein (CRP) concentration were measured. The administration of dioxidovanadium significantly alleviated hyperglycaemia with concomitant attenuation in oxidative stress as evidenced by reduced malondialdehyde concentrations. Furthermore, vanadium complex abolished diabetes-induced dyslipidaemia. Lastly, vanadium complex administration attenuated the increase in alanine aminotransferase, aspartate aminotransferase, and plasma C-reactive protein. These findings suggest that this metallo-compound (dioxidovanadium) may ameliorate liver dysfunction often observed in diabetes.

Abstract  We have developed a graphitic carbon nitride covered vanadium oxide nanocomposite (V2O5@g-C3N4) by a simple sonochemical approach (50 kHz and 150 W/cm2). Furthermore, the morphology and chemical composition of the V2O5@g-C3N4 nanocomposite was carried out by X-rays diffractometry (XRD), transmission electron microscopy (TEM) and electrochemical impedance spectroscopy (EIS). Furthermore, the V2O5@g-C3N4 nanocomposite modified electrode was investigate electrochemical behavior of the anticancer drug. Compared with bare SPCE, V2O5/SPCE and g-C3N4/SPCE, V2O5@g-C3N4 modified SPCE showed highest current response towards anti-cancer drug (methotrexate). Furthermore, the modified sensor exhibits with a sharp peaks and wide linear range (0.025-273.15 μM) by using DPV with the sensitivity of 7.122 μA μM-1 cm-2. Notably, we have achieved a nanomolar detection limit (13.26 nM) for the DPV detection of methotrexate. Further, the practicability of the V2O5@g-C3N4 nanocomposite modified sensor can be used for real time sensing of methotrexate in drug and blood serum samples with good recover ranges. It has potential applications in routine analysis with high specificity, excellent reproducibility and good stability.

Abstract  Association between short-term exposure to fine particulate matter (PM2.5) and mortality or morbidity varies geographically, and this variation could be due to different chemical composition affected by local sources. However, there have been only a few Asian studies possibly due to limited monitoring data. Using nationwide regulatory monitoring data of PM2.5 chemical components in South Korea, we aimed to compare the associations between daily exposure to PM2.5 components and mortality across six major cities. We obtained daily 24-h concentrations of PM2.5 and 11 PM2.5 components measured from 2013 to 2015 at single sites located in residential areas. We used death certificate data to compute the daily counts of nonaccidental, cardiovascular, and respiratory deaths. Using the generalized additive model, we estimated relative risks of daily mortality for an interquartile range increase in each pollutant concentration, while controlling for a longer-term time trend and meteorology. While elemental carbon was consistently associated with nonaccidental mortality across all cities, nickel and vanadium were strongly associated with respiratory or cardiovascular mortality in Busan and Ulsan, two large port cities. Our study shows that PM2.5 components responsible for PM2.5-associated mortality differed across cities depending on the dominant pollution sources, such as traffic and oil combustion.

Abstract  The reactivity of co-occurring arsenic (As) and uranium (U) in mine wastes was investigated using batch reactors, microscopy, spectroscopy, and aqueous chemistry. Analyses of field samples collected in proximity to mine wastes in northeastern Arizona confirm the presence of As and U in soils and surrounding waters, as reported in a previous study from our research group. In this study, we measured As (< 0.500 to 7.77 μg/L) and U (0.950 to 165 μg/L) in waters, as well as mine wastes (< 20.0 to 40.0 mg/kg As and < 60.0 to 110 mg/kg U) and background solids (< 20.0 mg/kg As and < 60.0 mg/kg U). Analysis with X-ray fluorescence (XRF) and electron microprobe show the co-occurrence of As and U with iron (Fe) and vanadium (V). These field conditions served as a foundation for additional laboratory experiments to assess the reactivity of metals in these mine wastes. Results from laboratory experiments indicate that labile and exchangeable As(V) was released to solution when solids were sequentially reacted with water and magnesium chloride (MgCl2), while limited U was released to solution with the same reactants. The predominance of As(V) in mine waste solids was confirmed by X-ray absorption near edge (XANES) analysis. Both As and U were released to solution after reaction of solids in batch experiments with HCO3-. Both X-ray photoelectron spectroscopy (XPS) and XANES analysis determined the predominance of Fe(III) in the solids. Mössbauer spectroscopy detected the presence of nano-crystalline goethite, Fe(II) and Fe(III) in (phyllo)silicates, and an unidentified mineral with parameters consistent with arsenopyrite or jarosite in the mine waste solids. Our results suggest that As and U can be released under environmentally relevant conditions in mine waste, which is applicable to risk and exposure assessment.

Abstract  Layer-structured vanadium oxide (V2O5) nanoribbons with efficient electron transport and short lithium ion insertion lengths are promising candidates for high-performance lithium-ion battery applications. Despite the extensive investigation of its electrochemical properties, the chemical and structural evolution during lithiation-delithiation processes has rarely been characterized in real time. Herein, the lithiation-delithiation behaviors of V2O5 nanoribbons are probed by in situ transmission electron microscopy. We reveal that the V2O5 nanoribbons exhibit high lithiation speed (0.8 nm/s) without retardation along the [010] direction and can be fully lithiated to the Li3V2O5 phase. Fully reversible retraction of lithium is observed in these V2O5 nanoribbons during delithiation. The lithiation process accompanying the coherent strain is further simulated by our phase field model. The simulation results reveal that the specific rough lithiation interface between the V2O5 and Li3V2O5 phases originates from the lithiation inhomogeneity.

Abstract  Paramagnetic molecules can show long spin-coherence times, which make them good candidates as quantum bits (qubits). Reducing the efficiency of the spin-phonon interaction is the primary challenge toward achieving long coherence times over a wide temperature range in soft molecular lattices. The lack of a microscopic understanding about the role of vibrations in spin relaxation strongly undermines the possibility of chemically designing better-performing molecular qubits. Here we report a first-principles characterization of the main mechanism contributing to the spin-phonon coupling for a class of vanadium(IV) molecular qubits. Post-Hartree-Fock and density functional theory methods are used to determine the effect of both intermolecular and intramolecular vibrations on modulation of the Zeeman energy for four molecules showing different coordination geometries and ligands. This comparative study provides the first insight into the role played by coordination geometry and ligand-field strength in determining the spin-lattice relaxation time of molecular qubits, opening an avenue to the rational design of new compounds.

Abstract  This study reports a clear-cut relationship of the technological use of specific filter aids with highly variable vanadium levels in beer, wine, and fruit juices. First, the previously reported broad range of vanadium levels was confirmed in 68 commercial beverages by ICP-MS. Since cloudy apple juices exhibited significantly lower vanadium amounts than clear apple juices, filter aids used for clarification were analyzed and found to contain substantial and highly variable amounts of vanadium, particularly in all analyzed diatomite (38-368 mg vanadium per kg filter aid), but not in perlite products (<4 mg/kg). Subsequent pilot-scale precoat filtration experiments (170 L/batch) proved vanadium to be released from diatomite (Kieselguhr), increasing its levels from ca. 2.1-2.6 µg/kg unfiltered to 27-201 µg/kg filtered juice, depending on the use of diatomites high or low in vanadium. Thus, filter aid selection was shown to modulate the vanadium concentrations in clarified beverages.

Abstract  BACKGROUND: The association of low-level exposure to metals and metal mixtures with cardiovascular incidence in the general population has rarely been studied. We flexibly evaluated the association of urinary metals and metal mixtures concentrations with cardiovascular diseases in a representative sample of a general population from Spain.

METHODS: Urine antimony (Sb), barium (Ba), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), molybdenum (Mo), vanadium (V) and zinc (Zn) were measured in 1171 adults without clinical cardiovascular diseases, who participated in the Hortega Study. Cox proportional hazard models were used for evaluating the association between single metals and cardiovascular incidence. We used a Probit extension of Bayesian Kernel Machine Regression (BKMR-P) to handle metal mixtures in a survival setting.

RESULTS: In single-metal models, the hazard ratios [confidence intervals (CIs)] of cardiovascular incidence, comparing the 80th to the 20th percentiles of metal distributions, were 1.35 (1.06, 1.72) for Cu, 1.43 (1.07, 1.90) for Zn, 1.51 (1.13, 2.03) for Sb, 1.46 (1.13, 1.88) for Cd, 1.64 (1.05, 2.58) for Cr and 1.31 (1.01, 1.71) for V. BKMR-P analysis was confirmatory of these findings, supporting that Cu, Zn, Sb, Cd, Cr and V are related to cardiovascular incidence in the presence of the other metals. Cd and Sb showed the highest posterior inclusion probabilities.

CONCLUSIONS: Urine Cu, Zn, Sb, Cd, Cr and V were independently associated with increased cardiovascular risk at levels relevant for the general population of Spain. Urine metals in the mixture were also jointly associated with cardiovascular incidence, with Cd and Sb being the most important components of the mixture.

Abstract  The development of chemically stable and high conductive membranes is one of the most important issues to improve the performance of vanadium flow batteries (VFBs). Herein, poly(vinylidene fluoride) (PVDF)/graphene composite nanoporous membranes were easily fabricated by manipulating crystallization processes. The graphene was used to enhance membrane selectivity and conductivity. In the nanoscale channels of the membranes, the graphene nanosheets reduced the apertures among the crystal grains, thus restraining vanadium ions crossover due to the size exclusion effect. Moreover, the oxygen groups on the graphene improved the surface hydrophilicity and formed hydrogen bonds with the PVDF polymer chains, which facilitated the proton transport. The composite membranes, with a 0.15 wt % graphene loading, showed a selectivity of 38.2 and conductivity of 37.1 mS/cm. The single cell exhibited a coulomb efficiency of 94.7%, a voltage efficiency of 88.5%, and an energy efficiency of 83.8%, which was 13% higher than that of the pristine PVDF membranes. The composite membranes showed excellent stability during 100 charge-discharge cycles. All these results indicate that the PVDF/graphene composite membrane is a promising candidate for VFB applications.

Abstract  The induced superconductivity (SC) in a robust and scalable quantum material with strong Rashba spin-orbit coupling is particularly attractive for generating topological superconductivity and Majorana bound states (MBS). Gold (111) thin film has been proposed as a promising candidate because of the large Rashba energy, the predicted topological nature, and the possibility for large-scale MBS device fabrications. We experimentally demonstrate two important steps towards achieving such a goal. We successfully show induced SC in the Shockley surface state (SS) of ultrathin Au(111) layers grown over epitaxial vanadium films, which is easily achievable on a wafer scale. The emergence of SC in the SS, which is physically separated from a bulk superconductor, is attained by indirect quasiparticle scattering processes instead of by conventional interfacial Andreev reflections. We further show the ability to tune the SS Fermi level (E_{F}) by interfacing SS with a high-κ dielectric ferromagnetic insulator EuS. The shift of E_{F} from ∼550 to ∼34  mV in superconducting SS is an important step towards realizing MBS in this robust system.

Abstract  The monovanadium-substituted polyoxometalate anion [VMo7O26]5-, exhibiting a β-octamolybdate archetype structure, was selectively prepared as pentapotassium [hexaikosaoxido(heptamolybdenumvanadium)]ate hexahydrate, K5[VMo7O26]·6H2O (VMo7), by oxidation of a reduced vanadomolybdate solution with hydrogen peroxide in a fast one-pot approach. X-ray structure analysis revealed that the V atom occupies a single position in the cluster that differs from the other positions by the presence of one doubly-bonded O atom instead of two terminal oxide ligands in all other positions. The composition and structure of VMo7 was also confirmed by elemental analyses and IR spectroscopy. The selectivity of the synthesis was inspected by a 51V NMR investigation which showed that this species bound about 95% of VV in the crystallization solution. Upon dissolution of VMo7 in aqueous solution, the [VMo7O26]5- anion is substantially decomposed, mostly into [VMo5O19]3-, α-[VMo7O26]4- and [V2Mo4O19]4-, depending on the pH.

Abstract  Vanadium accumulation levels in different tissues (muscle and organs) of the striped mullet Mugil cephalus (Linnaeus, 1758) and possible relationships with blood parameters were evaluated in a Natural Protected Area (Lake Faro, Sicily, Italy), during the winter of 2017. Hematological parameters (red blood cell, RBC; white blood cell, WBC; hemoglobin concentration, Hb; hematocrit, Hct; mean corpuscular volume, MCV; mean corpuscular hemoglobin, MCH; mean corpuscular hemoglobin concentration, MCHC; thrombocytes, TC), biometric indices (weight, total and fork length), and vanadium levels in muscles and organs (gills, liver, stomach and intestine) were determined. Statistical analyses showed significant differences in concentrations of vanadium of the analyzed tissue of M. cephalus and a positive relationship between vanadium concentration in the liver and some hematological parameters (RBC, Hb and Hct) and biometric indices. Our results underline the importance of fish blood parameters as sensitive indicators of toxic impact of environmental factors such as metals. This study, focusing on an ongoing topic, represents a valuable contribution to research concerning the monitoring and prevention of vanadium pollution in aquatic organisms and environments.

Abstract  Velocity map imaging has been employed to study multi-photon fragmentation of vanadium monoxide (VO) via the C 4Σ- state. The fragmentation dynamics are interpreted in terms of dissociation at the three-photon level, with the first photon weakly resonant with transitions to vibrational energy levels of the C 4Σ- state. The dissociation channels accessed are shown to depend strongly on the vibrational level via which excitation takes place. Analysis of the evolution of the kinetic energy release spectrum with photon energy leads to a refined value for the dissociation energy of ground state VO of D0(VO) = 53 126 ± 263 cm-1.

Abstract  The understanding of the catalyst-support interactions has been an important challenge in heterogeneous catalysis since the supports can play a vital role in controlling the properties of the active species and hence their catalytic performance. Herein, a series of isostructural mesoporous metal-organic frameworks (MOFs) based on transition metals, lanthanides, and actinides (Zr, Hf, Ce, Th) were investigated as supports for a vanadium catalyst. The vanadium species was coordinated to the oxo groups of the MOF node in a single-ion fashion, as determined by single-crystal X-ray diffraction, diffuse reflectance infrared Fourier transform spectroscopy, and diffuse reflectance UV-vis spectroscopy. The support effects of these isostructural MOFs were then probed using the aerobic oxidation of 4-methoxybenzyl alcohol as a model reaction. The turnover frequency was found to be correlated with the electronegativity and oxidation state of the metal cations on the supporting MOF nodes, highlighting an important consideration when designing catalyst supports.

Abstract  Vanadium dioxide (VO2) is a very promising cathode material for aqueous zinc ion batteries (AZIBs) because of its high reversible specific capacity, excellent rate performance and fast diffusion kinetics. However, its long-term cycle stability and compatibility with electrolytes have not met expectations. In this study, another metastable phase of vanadium dioxide-monoclinic VO2(D)-is demonstrated to be a better choice as a cathode for AZIBs. Electrochemical results revealed that the as-prepared VO2(D) hollow nanospheres delivered high reversible discharge capacity (up to 408 mA h g-1 at 0.1 A g-1), exceptional rate performance (200 mA h g-1 at 20 A g-1), and long cyclic endurance stability (cycling for 30 000 cycles with a low capacity fading rate of 0.0023% per cycle) in inexpensive 3 M ZnSO4 electrolyte. Furthermore, the electrochemical reaction mechanism was corroborated using ex situ XRD, HRTEM and XPS, showing that an interesting electrochemically induced phase transition from VO2(D) to V2O5·xH2O occured with the insertion/extraction of zinc ions. Finally, the prototype batteries assembled with our as-prepared VO2(D) hollow nanospheres and the impressive performance of this electrode under high active material mass loading further reveal its high potential in practical applications.

Abstract  Fungi are well known to strongly interact with metals, thereby influencing metal biogeochemistry in the terrestrial environment. To assess and quantify potential fungi-vanadium (V) interactions, Amanita muscaria, Armillaria cepistipes, Xerocomus badius and Bjerkandera adusta were cultured in media containing soluble V (VOSO4 or NaVO3) or solid-phase V of different chemical forms and oxidation state (V2O3, VO2, V2O5, or V-Ti magnetite slag). All fungi underwent physiological and structural changes, as revealed by alterations in FT-IR peak positions and intensities relative to the control, and morphological changes of mycelia, as observed by scanning electron microscopy. The diametric growth size generally decreased with decreasing oxidation state of V and with increasing concentrations of VOSO4 and NaVO3, implying that V toxicity is dependent on V speciation. The tolerance index, the ratio of treated and control mycelium (dry weight), shows different tendencies, suggesting additional factors influencing fungi weight, such as the formation of extrahyphal crystals. Vanadium accumulation from VOSO4 and NaVO3 medium in all fungi (up to 51.3 mg g-1) shows the potential of fungi to immobilise soluble V, thereby reducing its impacts on environmental and human health. Uptake and accumulation of V in slag was insignificant, reflecting the association of slag V with insoluble crystalline materials. The fungal accumulation of V in medium amended with V-oxides demonstrates the ability of fungi to solubilise solid-phase V compounds, thereby introducing previously immobile V into the V biogeochemical cycle and into the food chain where it may impact ecological and human health. A.muscaria lowered the pH of the medium substantially during cultivation, indicating acidolysis and complexolysis via excretion of organic acids (e.g. oxalic acid). Oxidation of VOSO4 was observed by a colour change of the medium to yellow during B. adusta cultivation, revealing the role of fungally-mediated redox transformation in V (im)mobilisation. The calculated removal efficiencies of soluble V were 40-90% for A. cepistipes and X. badius, but a much lower recovery (0-20%) was observed from V oxides and slag (0-20%) by all fungi. This suggests the probable application of fungi for bio-remediation of mobile/soluble V in contaminated soils but not of V incorporated in the lattice of soil minerals.

Abstract  Designing reconfigurable metasurfaces that can dynamically control scattered electromagnetic waves and work in the near-infrared (NIR) and optical regimes remains a challenging task, which is hindered by the static material property and fixed structures. Phase change materials (PCMs) can provide high contrast optical refractive indexes at high frequencies between amorphous and crystal states, therefore are promising as feasible materials for reconfigurable metasurfaces. Here, we propose a hybrid metasurface that can arbitrarily modulate the complex amplitude of incident light with uniform amplitude and full 2π phase coverage by utilizing composite concentric rings (CCRs) with different ratios of gold and PCMs. Our designed metasurface possesses a bi-functionality that is capable of splitting beams or generating vortex beams by thermal switching between metal and semiconductor states of vanadium oxide (VO2), respectively. It can be easily integrated into low loss photonic circuits with an ultra-small footprint. Our metadevice serves as a novel paradigm for active control of beams, which may open new opportunities for signal processing, memory storage, holography, and anti-counterfeiting.

Abstract  A local electric field is induced to engineer the interface of vanadium pentoxide nanofibers (V2 O5 -NF) to manipulate the charge transport behavior and obtain high-energy and durable supercapacitors. The interface of V2 O5 -NF is modified with oxygen vacancies (Vö) in a one-step polymerization process of polyaniline (PANI). In the charge storage process, the local electric field deriving from the lopsided charge distribution around Vö will provide Coulombic forces to promote the charge transport in the resultant Vö-V2 O5 /PANI nanocable electrode. Furthermore, an ≈7 nm porous PANI coating serves as the external percolated charge transport pathway. As the charge transfer kinetics are synergistically enhanced by the dual modifications, Vö-V2 O5 /PANI-based supercapacitors exhibit an excellent specific capacitance (523 F g-1 ) as well as a long cycling lifespan (110% of capacitance remained after 20 000 cycles). This work paves an effective way to promote the charge transfer kinetics of electrode materials for next-generation energy storage systems.

Abstract  The impact of oxydiacetate oxidovanadium(IV) complexes on plants is currently unknown. This report demonstrates the influence of these complexes on Arabidopsis thaliana (L.) Heynh. In the presence of 10-6M vanadium(IV) complexes, plants proceeded through their entire life cycle, with the occurrence of proper morphological and cytological organisation of leaf and root tissues. The addition of 10-1M H2O2 caused root damage, leaf necrosis, and plant death at around the seventh day, due to the destruction of the root system. Pretreatment of the plants with 10-6M of vanadium(IV) compounds: VOSO4 and VO(oda), alleviated the effects of H2O2 to some extent. Plants pretreated with 10-6M vanadium(IV) complexes survived longer despite the presence of H2O2. Considering the higher rate of plant survival in the presence of VOSO4, and the relatively high photosynthetic parameters and anthocyanin contents in the cells, we conclude that this vanadium(IV) compound can have positive effects on plants that are grown under stress conditions.

Abstract  A new antifluorite-type (Li2O-type) cubic compound, V2Se, has been synthesized for the first time by changing the amount of selenium in chemical vapor transport. The vanadium-based cubic phase studied here reveals a metal-metal bonding feature in the electronic band structure. This compound is the first example of an antifluorite-type cubic structure in a V-Se system.

Abstract  Herein, we report the homo- and co-polymerization of ethylene (E) with norbornene (NB) catalyzed by vanadium(III) phosphine complexes of the type VCl3(PMenPh3-n)2 [n = 2 (1a), 1 (1b)] and VCl3(PR3)2 [R = phenyl (Ph, 1c), cyclohexyl (Cy, 1d), tert-butyl (tBu, 1e)]. In the presence of Et2AlCl and Cl3CCOOEt (ETA), 1a-1e exhibit good activities for the polymerization of ethylene, affording linear, semicrystalline PEs with a melting temperature of approximately 130 °C. Mainly alternating copolymers with high comonomer incorporation were obtained in the E/NB copolymerization. A relationship was found between the electronic and steric properties of the phosphine ligands and the catalytic performance. Overall, the presence of electron-withdrawing ligand substituents increases the productivity, complexes with aryl phosphine (weaker σ-donor character) exhibiting a higher (co)polymerization initiation rate than those with alkyl phosphines (stronger σ-donor character). Steric effects also seem to play a key role since 1d and 1e, having large size phosphines (PCy3 θ = 170° and PtBu3 θ = 182°, respectively) are more active than 1a (PMe2Ph θ = 122°). In this case, the larger size of PtBu3 and PCy3 likely compensates for their higher donor strength compared to PMe2Ph.

Abstract  Trophic transfer of contaminants dictates concentrations and potential toxic effects in top predators, yet biomagnification behaviour of many trace elements is poorly understood. We examined concentrations of vanadium and thallium, two globally-distributed and anthropogenically-enriched elements, in a food web of the Slave River, Northwest Territories, Canada. We found that tissue concentrations of both elements declined with increasing trophic position as measured by δ15N. Slopes of log [element] versus δ15N regressions were both negative, with a steeper slope for V (-0.369) compared with Tl (-0.099). These slopes correspond to declines of 94% with each step in the food chain for V and 54% with each step in the food chain for Tl. This biodilution behaviour for both elements meant that concentrations in fish were well below values considered to be of concern for the health of fish-eating consumers. Further study of these elements in food webs is needed to allow a fuller understanding of biomagnification patterns across a range of species and systems.

Abstract  We report a dynamically tunable reflectarray metasurface that continuously modulates the phase of reflected light in the near-infrared wavelength range under active electrical control of the phase transition from semiconducting to semimetallic states. We integrate a vanadium dioxide (VO2) active layer into the dielectric gap of antenna elements in a reflectarray metasurface, which undergoes an insulator-to-metal transition upon resistive heating of the metallic patch antenna. The induced phase transition in the VO2 film strongly perturbs the magnetic dipole resonance supported by the metasurface. By carefully controlling the volume fractions of coexisting metallic and dielectric regions of the VO2 film, we observe a continuous shift of the phase of the reflected light, with a maximal achievable phase shift as high as 250°. We also observe a reflectance modulation of 23.5% as well as a spectral shift of the resonance position by 175 nm. The metasurface phase modulation is fairly broadband, yielding large phase shifts at multiple operation wavelengths.

Abstract  Developing efficient and low-cost bifunctional electrocatalysts as candidates for Pt-based materials to satisfy commercial applications in the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) is still very challenging. Herein, we show that Co,N-codoped porous vanadium nitride (VCoN) nanoplates are successfully synthesized via a simple one-step pyrolysis protocol without the use of NH3 gas. We also demonstrate that the crystallization, surface chemical state and porosity of vanadium nitride are well modulated by inventively using Co dopants as structural inducers. The resulting VCoN material exhibits an excellent catalytic activity towards the HER in alkaline media, with an extremely low onset potential of -0.03 V, an overpotential of 179 mV at 10 mA cm-2, and a remarkable durability for over 100 h. Moreover, it shows a superior ORR performance, which compares favorably with commercial 20% Pt/C, exhibiting an onset potential of ∼1.02 V, a half-wave potential of ∼0.91 V and a weak potential shift (-5 mV) after 2000 cycles at 1600 rpm in 0.1 M KOH. Such excellent electrocatalytic performance primarily contributes to the unique structural features of the heteroatom N (pyrrolic and graphitic N) and Co codoping in favor of improving the electrical conductivity and the high porosity contributing to exposing numerous catalytic active sites.

Abstract  In this work, we report a sensitive and selective electrochemical sensor for the detection of dopamine (DA) neurotransmitter based on VS2-SnS2/f-MWCNT hybrids. Herein, the binary metal sulfide (VS2-SnS2) was synthesized via single step hydrothermal route and hybrids with f-MWCNT via the ultrasonication process. The as-prepared VS2-SnS2/f-MWCNT hybrids were characterized through the FESEM, EDX and elemental mapping, TEM, XPS, Raman and XRD techniques. The electrochemical performance and catalytic activity of the modified electrodes were probed using electrochemical impedance spectra (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Interestingly, DPV results exhibits an appreciable linear range from 0.025 to 1017 μM and LOD of 0.008 μM. The selectivity study was performed to prove the high selectivity of the VS2-SnS2/f-MWCNT hybrids modified electrode. Furthermore, the practical applicability of the DA sensor was scrutinized in human serum sample and rat brain sample.