Charged Sites Research Articles

Mathematical Modelling of Glyphosate Molecularly Imprinted Polymer-Based Microsensor with Multiple Phenomena.

The massive and careless use of glyphosate (GLY) in agricultural production raises many questions regarding environmental pollution and health risks, it is then important to develop simple methods to detect it. Electrochemical impedance spectroscopy (EIS) is an effective analytical tool for characterizing properties at the electrode/electrolyte interface. It is useful as an analytical procedure, but it can also help in the interpretation of the involved fundamental electrochemical and electronic processes. In this study, the impedance data obtained experimentally for a microsensor based on molecularly imprinted chitosan graft on 4-aminophenylacetic acid for the detection of glyphosate was analyzed using an exact mathematical model based on physical theories. The procedure for modeling experimental responses is well explained. The analysis of the observed impedance response leads to estimations of the microscopic parameters linked to the faradic and capacitive current. The interaction of glyphosate molecules with the imprinted sites of the CS-MIPs film is observed in the high frequency range. The relative variation of the charge transfer resistance is proportional to the log of the concentration of glyphosate. The capacitance decreases as the concentration of glyphosate increases, which is explained by the discharging of the charged imprinted sites when the glyphosate molecule interacts with the imprinted sites through electrostatic interactions. The phenomenon of adsorption of the ions in the CMA film is observed in the low frequency range, this phenomenon being balanced by the electrostatic interaction of glyphosate with the imprinted sites in the CS-MIPs film.

Simulation of Electric Vehicle Charging Points Based on Efficient Use of Chargers and Using Recuperated Braking Energy from Trains

Electric vehicles represent an innovation in mobility that can help significantly reduce greenhouse emissions and mitigate climate change. However, replacing internal combustion with electric vehicles is not enough. This replacement needs to be complemented with a change in the energy mix of individual countries towards renewable energy sources and efficient use of electricity generated as a secondary product. Recuperative braking energy from trains can serve as one source of such secondary energy. Following an analysis of recuperative energy generated and analysis of charging requirements of individual electric vehicles, the paper proposes a model of a charging site near train stations. Using this energy to charge electric vehicles helps to reduce energy consumption from the electricity grid and thus reduce carbon emissions. Compared to other articles, the proposed model ensures the efficient use of recuperative braking energy from trains by using the variable charging power function; thereby, the installation of additional battery storage is eliminated. Our model results show that the benefits of a car park with a reservation system near train stations increase the car park efficiency, provide a sufficient number of private charging points, contribute to efficient use of recovered energy, and reduce carbon emissions.

Paraquat sorption- and organic matter-induced modifications of soil spectral induced polarization (SIP) signals

SUMMARY Quantifying the capacity of soils to immobilize sorbing contaminants of concern relies on batch sorption experiments, typically performed at skewed solid-to-liquid ratios. The geophysical method spectral induced polarization (SIP) provides a powerful non-invasive monitoring alternative that can capture changes in soil electrical properties driven by contaminant sorption, yielding an approach whereby immobilization can be monitored in situ. Here, we present SIP signals obtained from a series of columns packed with a water saturated natural sandy-loam soil, with and without solid organic matter (SOM) amendment, contaminated with increasing concentrations of the herbicide paraquat. Our results highlight that soil polarization drops proportional to increasing amounts of sorbed paraquat in the SOM-free soil, exhibiting a Langmuir-type leveling-off behaviour. The addition of 8 percent-SOM yielded an increase in both the real ($\sigma ^{\prime}$) and imaginary ($\sigma ^{\prime\prime}$) conductivity of the uncontaminated treatment, driven by the contribution of charged sites in the SOM. Further, SOM modified the dependence between $\sigma ^{\prime\prime}$ and sorbed paraquat, likely driven by continued polarization within the polydisperse SOM with continued paraquat addition. However, the time constant ($\tau $), derived using the Cole–Cole model, shed light on a saturation-type dependence governed by a drop in ion mobility with increasing sorption. Thus, aiding the interpretation of sorption-driven SIP signals.

Intermetallic YIr2 nanoparticles with negatively charged Ir active sites for catalytic hydrogenation of cyclohexanone to cyclohexanol

Negatively charged iridium species in Laves phase YIr2 as highly active sites for hydrogenation of cyclohexanone to cyclohexanol.

Detection of superoxide radical in all biological systems by Thin Layer Chromatography

The study presents a new method that detects O2•−, via quantification of 2-hydroxyethidium (2-ΟΗ-Ε+) as low as ∼30 fmoles by High-Performance Thin Layer Chromatography (HPTLC). The method isolates 2-ΟΗ-Ε+ after its extraction by the anionic detergent SDS (at 18-fold higher than its CMC) together with certain organic/inorganic reagents, and its HPTLC-separation from di-ethidium (di-Ε+) and ethidium (Ε+). Quantification of 2-OH-E+ is based on its ex/em maxima at 290/540 nm, and of di-E+ and E+ at 295/545 nm. The major innovations of the present method are the development of protocols for (i) efficient extraction (by SDS) and (ii) sensitive quantification (by HPTLC) for 2-OH-E+ (as well as di-E+ and E+) from most biological systems (animals, plants, cells, subcellular compartments, fluids). The method extracts 2-ΟΗ-Ε+ (by neutralizing the strong binding between its quaternary N+ and negatively charged sites on phospholipids, DNA etc) together with free HE, while protects both from biological oxidases, and also extracts/quantifies total proteins (hydrophilic and hydrophobic) for expressing O2•− levels per protein quantity. The method also uses SDS (at 80-fold lower than its CMC) to extract/remove/wash 2-ΟΗ-Ε+ from cell/organelle exterior membrane sites, for more accurate internal content quantification. The new method is applied on indicative biological systems: (1) artificially stressed (mouse organs and liver mitochondria and nuclei, ±exposed to paraquat, a known O2•− generator), and (2) physiologically stressed (cauliflower plant, exposed to light/dark).

Cooperative Adsorption of Nonionic Triton X-100 and Dodecyldimethylamine Oxide Surfactant Mixtures at the Hydrophilic Silica-Water Interface Studied by Total Internal Reflection Raman Spectroscopy and Multivariate Curve Resolution.

The adsorption of dimethyldodecylamine oxide (DDAO) and Triton X-100 (TX) as single components and mixed systems at the silica-water interface has been studied using total internal reflection (TIR) Raman spectroscopy combined with multivariate curve resolution (MCR). In this study, the mixtures of DDAO and TX indicate minimal synergism in the bulk solution; however, the cooperative adsorption behavior on the silica surface is shown with various mixtures of DDAO (up to 1.3 mM) and TX (up to 1.1 mM). Adding the DDAO (up to 0.3 mM) to TX solution, the surface excess of TX shows 30% enhancement, from 1.2 to 1.8 μmol m-2. Adding the DDAO also shifts the TX adsorption isotherms, resulting in the Gibbs free energy change of -2.87 ± 0.73 kJ mol-1. This free energy change is interpreted as the decrease in surface energy when the silica surface charged sites are screened by the DDAO adsorbed layer. Alternatively, when a DDAO solution contains a small amount of TX molecules, i.e., < 30 μM, its adsorption on the silica surface quickly equilibrates. In addition, the formation of a more ordered liquid-crystalline adsorbed layer, as in the case of single-component DDAO adsorption, is not observed.

Mechanisms Responsible for Adsorption of Molybdate ions on Alumina for the Production of Medical Radioisotopes

Abstract In this work, the mechanisms responsible for the adsorption of molybdate ions on alumina are investigated using in-depth surface analyses of alumina specimens immersed in solutions containing different molybdate ions at different pH values. The obtained results reveal that when alumina is immersed in an acidic solution containing molybdate ions, the hydroxyl groups present on the surface are removed to generate positively charged sites, and molybdate ions (MoO42− or AlMo6O24H63−) are adsorbed via an electrostatic interaction. Alumina dissolves slightly in an acidic solution to form AlMo6O24H63−, which is more easily desorbed than MoO42−. Furthermore, the enhancement in the Mo adsorption or desorption property may be achieved by enriching the surface of the alumina adsorbent with many –OH groups and optimizing Mo solution to adsorb molybdate ions on alumina as MoO42− ions. These findings will assist researchers in engineering more efficient and stable alumina-based adsorbents for molybdenum adsorption used in medical radioisotope (99Mo/99mTc) generators.

An approach for quantum capacitance of graphene, carbon nanotube, silicene and hexagonal boron nitride nanoscale supercapacitors by non-equilibrium Green’s function method

We introduce a comprehensive approach to calculate quantum capacitance of nanoscale capacitors as a function of applied potential difference to have resemblance to actual device operating conditions. Ab initio analysis based on the non-equilibrium Green’s functions combined with density functional theory was applied for different elementary materials and geometries for the soundness of the approach. The results of planar single layer graphene, silicene, and hexagonal boron nitride and for tubular carbon nanotube supercapacitor symmetric model systems on the quantum capacitance are presented together with widely utilized fixed band approximation at planar systems for comparison purposes. The proposed procedure not only successfully reproduced the results for planar systems in a qualitative manner but is also consistently applicable for non-planar (tubular) systems by remarking the robustness of the procedure. Our work highlights the importance of the separation spacing (such as contact distance) search in obtaining quantum capacitance for electric double layer supercapacitors. In that search procedure, it is basically aimed to minimize the charge on the leads/plates for eliminating quantum effects. Induced charge sites under the applied bias could be indicative in some degree for the possible ion adsorption/desorption from the electrolyte or redox reactions at electrode/electrolyte interface to create a double layer. So that the proposed approach on the presented study could also be treated as a qualitative measure on the quantum capacitance for realistic systems with dopants, defects, and functional groups for supercapacitor understanding.

Mix-charged polyamide membranes via molecular hybridization for selective ionic nanofiltration

Nanofiltration membranes that can selectively remove multivalent ions from salty water hold great promise in water treatment and salt utilization. However, developing nanofiltration membranes with high rejection to both divalent anions and cations remains a grand challenge. Herein, we design a kind of mix-charged polyamide membranes (MCPMs) via molecular hybridization to achieve the removal of versatile divalent ions. Amino-functionalized polyhedral oligomeric silsesquioxane (NH2-POSS) was employed as molecular filler added into piperazine and reacted with trimesoyl chloride at the aqueous-organic interface to generate cross-linked polyamide-NH2-POSS mixed network. The protonated amino groups from NH2-POSS offered positively charged sites for enhanced divalent cation repulsion while the deprotonated carboxyl groups from polyamide network can afford negatively charged sites for divalent anion repulsion. The optimized membrane displayed high rejections to both divalent anionic and cationic ions (Na2SO4 rejection of 98.2%, MgCl2 rejection of 98.0%), together with high mono-/divalent salt selectivity (NaCl/Na2SO4 of 48.2, LiCl/MgCl2 of 43.9) that outperformed the benchmark nanofiltration membranes. This molecularly-hybridized charge modulation method may enlighten the structural design of membranes for efficient ionic separations.

Decolonising Love

This article reconsiders Frank Bowling’s figurative paintings from the early 1960s, emphasising the recurrence of intimate affects in this body of works. It argues that the representation of romantic entanglements is cardinal rather than marginal in this artist’s negotiation of both personal and pictorial freedoms. This becomes especially clear when Bowling’s early work is set against the backdrop of nativist anxieties about the growing visibility of interracial unions in postwar Britain. With this in mind, and in a nod to the growing literature on love and anti-racist resistance, the article presents affective relationships and their visual manifestations as charged sites for the renegotiation of unequal power relations. Not only does this analysis restore political substance to a series of paintings that is rarely considered by scholars of Bowling’s work, but points toward new ways of reassessing the field of mid-twentieth century modernism in terms of diasporic and intersectional phenomenologies of desire.

Molecular Basis for the Remarkably Different Gas-Phase Behavior of Deprotonated Thyroid Hormones Triiodothyronine (T3) and Reverse Triiodothyronine (rT3): A Clue for Their Discrimination?

Thyroid hormones are biologically active small molecules responsible for growth and development regulation, basal metabolic rate, and lipid and carbohydrate metabolism. Liquid chromatography mass spectrometry (LC–MS) can be used to quantify thyroid hormones blood level with high speed and selectivity, aiming to improve the diagnosis and treatment of the severe pathological conditions in which they are implicated, i.e., hypo- and hyperthyroidism. In this work, the gas-phase behavior of the isomeric thyroid hormones triiodothyronine (T3) and reverse triiodothyronine (rT3) in their deprotonated form was studied at a molecular level using MS-based techniques. Previously reported collision-induced dissociation experiments yielded distinct spectra despite the high structural similarity of the two compounds, suggesting different charge sites to be responsible. Infrared multiple photon dissociation spectroscopy on [T3-H]− and [rT3-H]− was performed, and the results were interpreted using DFT and MP2 calculations, assessing the prevalence of T3 in the carboxylate form and rT3 as a phenolate isomer. The different deprotonation sites of the two isomers were also found to drive their ion-mobility behavior. In fact, [T3-H]− and [rT3-H]− were successfully separated. Drift times were correlated with collisional cross section values of 209 and 215 Å2 for [T3-H]− and [rT3-H]−, respectively. Calculations suggested the charge site to be the main parameter involved in the different mobilities of the two anions. Finally, bare [T3-H]− and [rT3-H]− were made to react with neutral acetylacetone and trifluoroacetic acid, confirming rT3 to be more acidic than T3 in agreement with the calculated gas-phase acidities of T3 and rT3 equal to 1345 and 1326 kJ mol–1, respectively.

High-Performance Electrochemical NO Reduction into NH3 by MoS2 Nanosheet.

Electrochemical reduction of NO not only offers an attractive alternative to the Haber-Bosch process for ambient NH3 production but mitigates the human-caused unbalance of nitrogen cycle. Herein, we report that MoS2 nanosheet on graphite felt (MoS2 /GF) acts as an efficient and robust 3D electrocatalyst for NO-to-NH3 conversion. In acidic electrolyte, such MoS2 /GF attains a maximal Faradaic efficiency of 76.6 % and a large NH3 yield of up to 99.6 μmol cm-2 h-1 . Using MoS2 nanosheet-loaded carbon paper as the cathode, a proof-of-concept device of Zn-NO battery was assembled to deliver a discharge power density of 1.04 mW cm-2 and an NH3 yield of 411.8 μg h-1 mgcat. -1 . Calculations reveal that the positively charged Mo-edge sites facilitate NO adsorption/activation via an acceptance-donation mechanism and disfavor the binding of protons and the coupling of N-N bond.

Impact of Nonspecific Adsorption to Metal Surfaces in Ion Pair-RP LC-MS Impurity Analysis of Oligonucleotides

Nonspecific adsorption has been a consistent challenge in the analysis of oligonucleotides. Nonspecific adsorption is a result of interactions between charged acidic analytes and adsorption sites present in metallic surfaces located in the fluidic path of chromatography systems. Due to their high surface area, adsorption to column frits is especially concerning. Poor peak shape, low recovery and compromised LOQ have been associated with this phenomenon. Alternative methods including substitution of stainless steel for different hardware materials and mobile phase additives have been explored in an attempt to minimize this issue. Chemical modification of metal surfaces using hybrid surface technology (HST) by-passes the limitation of stainless steel construction material by forming a hybrid organic/inorganic layer that acts as a barrier and limits nonspecific interactions. In this study we explore the implications of this new technology in sensitive analysis and determination of relative impurity levels of oligonucleotides. Higher relative impurity levels and better reproducibility were obtained with columns using HST.

A novel Janus sponge fabricated by a green strategy for simultaneous separation of oil/water emulsions and dye contaminants

A novel Janus sponge with the ability to remove complex contaminants from water is reported. Firstly, a superhydrophilic sponge (PA@PEI-sponge) is prepared via synthesizing negatively charged phytic acid@polyethyleneimine (PA@PEI) nanoparticles and assembling them on the surface of polydopamine (PDA) and PEI-modified polyurethane (PU) sponge through electrostatic adsorption. The Janus sponge is generated by modifying one side of the PA@PEI-sponge with PDMS, which exhibits superior separation efficiency and high filtration flux toward both water-in-oil and oil-in-water emulsions due to its multiplex selective wettability and the interconnected and tortuous 3D porous channels. The numerous negatively charged active sites of PA@PEI nanoparticles and PDA layer impart the superhydrophilic PA@PEI-sponge with the removal efficiency of 39.95 ± 0.27% for malachite green (MG) via simple flow-through filtration, which can be improved to 99.92 ± 0.07% by Janus modification. More importantly, the Janus sponge exhibits an excellent treatment capacity for complex mixtures containing emulsified oil and dye, with the separation efficiency above 99.59%. The Janus sponge also demonstrates the effective separation of real industrial wastewater collected from an acrylic dyeing plant. Together with a facile and green preparation strategy, this Janus sponge shows excellent application potential for simultaneous dye removal and oil/water emulsion separation.

Morphology alteration of nickel microstructures for glycerol electrooxidation

Shape-controlled microstructures (triangles and urchin-like) of Ni were synthesized using polyol synthesis in the presence/absence of capping agent (polyvinilpyrrolidone, PVP). Direct visualization of crystal structure and morphology before/after electrochemical tests in KOH were characterized using electron microscopy techniques. Electrochemical characterizations illustrated that urchin-Ni-PVP has highest catalytic activity among all investigated electrocatalysts for glycerol electrooxidation reaction (GEOR). Improved activity was attributed to the surface area and the highly porous structure as identified by electron tomography analysis. All Ni shapes showed similar selectivity. DFT calculations on low-index β-NiOOH and β-Ni(OH)2 planes were performed as possible surfaces present during electrochemical processes. The (001) surface is the most thermodynamically stable in both systems and has different possible terminations. For O, Ni and mixed Ni-O atoms terminations the β-NiOOH(001) present metallic behavior. DFT results show that either Ni or Ni-O exposed β-NiOOH(001) surfaces are possible scenarios for glycerol adsorption on different catalytic charged surface sites.

Hidden Halogen-Bonding Ability of Fluorine Manifesting in the Hydrogen-Bond Configurations of Hydrogen Fluoride.

Elucidating how the intermolecular interactions of a covalently bonded fluorine atom are similar to and different from those of the other halogen atoms will be helpful for a better unified understanding of them. In the present study, the case of hydrogen fluoride is theoretically studied from this viewpoint by using the techniques of electron density analysis, molecular dynamics of liquid, and others. It is shown that the extra-point model, which locates an additional charge site on the line extended from (not within) the covalent bond and has been adopted for halogen-bonding systems as a key to the generation of proper stability and directionality, works well also in this case. A significantly bent hydrogen-bond configuration, which is characteristic of the intermolecular interactions of hydrogen fluoride, is reasonably well reproduced, meaning that it is a manifestation of the latent halogen-bonding ability, which is hidden by the strongly electronegative nature.

Ionic Transport and Thermodynamic Interaction in Precision Polymer Blend Electrolytes for Lithium Batteries

AbstractSingle‐ion conducting polymer electrolytes are of interest for use with advanced battery electrodes such as lithium metal, but achieving sufficiently high conductivity has been challenging. In this work, a model system containing charged sites that are precisely spaced along the polymer backbone is explored. Precision sulfonated poly(4‐phenylcyclopentene) lithium salt (p5PhS‐Li) with a high degree of sulfonation (&gt; 90%) is synthesized and blended with poly(ethylene oxide) (PEO) to investigate the thermodynamic and transport properties. Melting point depression is measured via differential scanning calorimetry, ionic conductivity,κ, is determined using electrochemical impedance spectroscopy, and the fraction of current carried by Li+is estimated based on steady‐state current measurements. In conjunction with a density measurement, melting point depression is used to find an effective Flory–Huggins interaction parameter,χeff= − 0.21, suggesting miscibility of the blend.κspans a large range from 2 × 10−11to 2 × 10−7S cm−1over the composition and temperature range investigated. The fraction of charge carried by lithium ions also spans a significant range from 0.12 in majority PEO blend to 0.98 in majorityp5PhS‐Li blend. This study addresses several limitations of sulfonated polystyrene and opens up the possibility of precisely controlling the spacing of other anion types.

Effect of Coordination Environment Surrounding a Single Pt Site on the Liquid-Phase Aerobic Oxidation of 5-Hydroxymethylfurfural.

As the frontier in heterogeneous catalyst, a monomer and positively charged active sites in the single-atom catalyst (SAC), anchored by high electronegative N, O, S, P, etc., atoms, may not be active for the multispecies (O2, substrates, intermediates, solvent etc.) involved liquid-phase aerobic oxidation. Here, with catalytic, aerobic oxidation of 5-hydroxymethylfurfural as an example, Pt SAC (Pt1-N4) was synthesized and tested first. With commercial Pt/C (Pt loading of 5 wt %) as a benchmark, 2,5-furandicarboxylic acid (FDCA) yield of 97.6% was obtained. Pt SAC (0.56 wt %) gave a much lower FDCA yield (28.8%). By changing the coordination atoms from highly electronegative N to low electronegative Co atoms, the prepared Pt single-atom alloy (SAA, Pt1-Co3) catalyst with ultralow Pt loading (0.06 wt %) gave a much high FDCA yield (99.6%). Density functional theory (DFT) calculations indicated that positively charged Pt sites (+0.712e) in Pt1-N4 almost lost the capability for oxygen adsorption and activation, as well as the adsorption for the key intermediate. In Pt1-Co3 SAA, the central negatively charged Pt atom (-0.446e) facilitated the adsorption of the key intermediate; meanwhile, the nearby Co atoms around the Pt atom constituted the O2-preferred adsorption/activation sites. This work shows the difference between the SAC with NPs and the SAA during liquid-phase oxidation of HMF and gives a useful guide in the future single-atom catalyst design in other related reactions.

Day-Ahead Forecast of Electric Vehicle Charging Demand with Deep Neural Networks

The increasing penetration rate of electric vehicles, associated with a growing charging demand, could induce a negative impact on the electric grid, such as higher peak power demand. To support the electric grid, and to anticipate those peaks, a growing interest exists for forecasting the day-ahead charging demand of electric vehicles. This paper proposes the enhancement of a state-of-the-art deep neural network to forecast the day-ahead charging demand of electric vehicles with a time resolution of 15 min. In particular, new features have been added on the neural network in order to improve the forecasting. The forecaster is applied on an important use case of a local charging site of a hospital. The results show that the mean-absolute error (MAE) and root-mean-square error (RMSE) are respectively reduced by 28.8% and 19.22% thanks to the use of calendar and weather features. The main achievement of this research is the possibility to forecast a high stochastic aggregated EV charging demand on a day-ahead horizon with a MAE lower than 1 kW.

Fabrication of high performance Mg2+/Li+ nanofiltration membranes by surface grafting of quaternized bipyridine

A new monomer (quaternized bipyridine, QBPD) was synthesized to modify the interfacially polymerized polyethyleneimine (PEI) membranes. The QBPD monomer, containing binary charge sites and amine groups (NH2), was anchored to the pristine PEI membrane through the “amine ∼ acyl chloride” amidation reaction. Pure water flux of the QBPD membrane is ∼ 96.6 L m−2h−1 while the MgCl2 rejection is maintained at 92%±3. Noteworthy, the flux is ∼ 2.8 times as high as that of the pristine PEI membrane (∼34.0 L m−2h−1 at 0.6 MPa). Meanwhile, separation performance of the QBPD membrane remains stable in 162 h operation time at 0.6 MPa. When filtrating 50:1 Mg2+/Li+ mixture, the flux of the QBPD membrane is 81.6 L m−2h−1, and the Mg/Li ratio in the permeate was reduced to 8.5:1. Collectively, the QBPD membrane shows good performance compared with recent nanofiltration membranes for Mg2+/Li+ separation, exhibiting considerable potential for lithium extraction from salt lakes with high Mg2+/Li+ ratio.