Polar Ion Research Articles

Nanopatterning of the (001) surface of crystalline Ge by ion irradiation at off-normal incidence: Experiment and simulation

Intricate topographical patterns can form on the surface of crystalline Ge(001) subject to low-energy ion irradiation in the reverse epitaxy regime, i.e., at elevated temperatures which enable dynamic recrystallization. We compare such nanoscale patterns produced by irradiation from varied polar and azimuthal ion incidence angles with corresponding calculated surface topographies. To this end, we propose a continuum equation including both anisotropic erosive and anisotropic diffusive effects. Molecular dynamics simulations provide the coefficients of angle-dependent sputter erosion for the calculations. By merely changing these coefficients accordingly, the experimentally observed surface morphologies can be reproduced, except for extreme ion incidence angles. Angle-dependent sputter erosion is thereby identified as a dominant mechanism in ion-induced pattern formation on crystalline surfaces under irradiation from off-normal incidence angles.

Operando high-temperature near-ambient pressure X-ray photoelectron spectroscopy and impedance spectroscopy study of [formula omitted] solid oxide fuel cell anode

In this study we present the results of operando high temperature near-ambient-pressure x-ray photoelectron spectroscopy (HT-NAP-XPS) measurements of a pulsed laser deposited thin film Ni−Ce0.9Gd0.1O2−δ model electrode. In our measurements, we have used the novel three electrode dual-chamber electrochemical cell developed in our previous work at different H2 pressures and at different electrochemical conditions at around 650 °C.The possible redox reactions on the anode surface (Ni2+↔Ni0,Ce4+↔Ce3+) were investigated by HT-NAP-XPS technique simultaneously with electrochemical impedance spectroscopy measurements. The oxygen partial pressure in counter and reference electrode compartment was controlled at 0.2 bar. Changes in electronic structure of the Ce3d and Ni2p photoelectron spectra caused by electrode potential and H2 pressure variations were observed and estimated by curve fitting procedure. The O1s and valence band photoelectron signals were used for depth probing of the chemical composition and redox changes at Ni-GDC and for studying the influence of the electrochemical polarization on the chemical state of Ni-GDC surface atoms.As a result changes in oxidation state of electrode surface atoms caused by electrode polarization and oxide ion flux through the membrane were detected with simultaneous significant variation of electrochemical impedance.

Molecular Dynamics Simulation Study of a CO₂-Switchable Surfactant.

We computed molecular properties of a long-tail amidine surfactant (N'-dodecyl-N,N-dimethylacetamidinium bicarbonate, DDAB) through quantum mechanics (QM) method. We then used molecular dynamics (MD) computations to obtain the properties of DDAB when displaced from the center to the boundary surface. The QM calculation results indicated that the mono-dentate type of bindings between polar head group and HCO-₃ ion was more likely to be adopted. The MD results indicated that the HCO-₃ ions could pass the energy barrier surrounding the head groups to form stable ion pairs. Meanwhile, the surfactant molecules aggregated very quickly, and absorbed in a direction pointed from the bulk center to the boundary. These results indicated that hydrophobic correlations of alkyl chains are the driving force for boundary adsorption of DDAB.

Evolution of the Earth's Polar Outflow From Mid‐Archean to Present

AbstractThe development of habitable conditions on Earth is tightly connected to the evolution of its atmosphere, which is strongly influenced by atmospheric escape. We investigate the evolution of the polar ion outflow from the open field line bundle, which is the dominant escape mechanism for the modern Earth. We perform Direct Simulation Monte Carlo (DSMC) simulations and estimate the upper limits on escape rates from the Earth's open field line bundle starting from 3 gigayears ago (Ga) to present assuming the present‐day composition of the atmosphere. We perform two additional simulations with lower mixing ratios of oxygen of 1% and 15% to account for the conditions shortly after the Great Oxydation Event (GOE). We estimate the maximum loss rates due to polar outflow 3 gigayears ago of 3.3×1027 s−1 and 2.4×1027 s−1 for oxygen and nitrogen, respectively. The total integrated mass loss equals to 39% and 10% of the modern atmosphere's mass, for oxygen and nitrogen, respectively. According to our results, the main factors that governed the polar outflow in the considered time period are the evolution of the XUV radiation of the Sun and the atmosphere's composition. The evolution of the Earth's magnetic field plays a less important role. We conclude that although the atmosphere with the present‐day composition can survive the escape due to polar outflow, a higher level of CO2 between 3.0 and 2.0 Ga was likely necessary to reduce the escape.

Understanding the role of water-soluble guar gum binder in reducing capacity fading and voltage decay of Li-rich cathode for Li-ion batteries

The practical application of high-capacity Li-rich cathode materials is hindered by capacity fading and voltage decay. The capacity fading and voltage decay could be effectively overcome by using water-soluble guar gum (GG) binder instead of traditional polyvinylidene fluoride (PVDF). However, the specific role of the GG binder is not clear yet, though the GG binder can significantly improve the electrochemical performance of Li-rich cathode. To understand the effect of GG binder on the morphology, microstructure of electrode and electrode/electrolyte interfaces, ex-situ scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray adsorption near edge spectroscopy (XANES), in-situ electrochemical impedance spectroscopy (EIS) were applied to comparatively study the charge-discharge processes of Li-rich Li1.2Ni0.2Mn0.6O2 cathode when using GG and PVDF as binders. The results indicate that the GG binder can prevent electrode crack and active material loss, ascribing to the strong mechanical adhesion of GG binder with active material particles and current collector. It has found that the GG binder can also induce the formation of a uniform layer on Li1.2Ni0.2Mn0.6O2 particles’ surface. As a consequence, both the electrolyte decomposition and the electrode corrosion were significantly inhibited. The strong chelation between Mn2+ and polar OH group restrain Mn ion dissolution, which contributes to surface structural transformation mitigation. The present study reveals the role of water-soluble GG binder in reducing capacity fading and voltage decay of Li-rich material and is of great importance in design functional binders for high-performance Li-rich electrodes.

Effect of the Sulfonation on the Swollen State Morphology of Styrenic Cross-Linked Polymers.

The chemical structure and morphology of a set of sulfonic gel-type poly(styrene-divinylbenzene) resins (2 mol% DVB) prepared with different synthetic approaches were investigated by solid state NMR, Inverse Size Exclusion Chromatography (ISEC), FT-IR and elemental analysis to compare their swollen state structure. FT-IR and solid state NMR clearly show that the sulfonation mainly occurs in the para- position with respect the main polymer chain. Sensible proportions of sulfone bridges were found in the materials obtained with oleum and chlorosulfonic acid. With oleum, the presence of the sulfone bridges is clearly associated to a reduced ability to swell in the water medium relative to the proton exchange capacity. This highlights the cross-linking action of the sulfone bridges according to ISEC results, showing a high proportion of a dense polymer fraction in the swollen material. An even higher degree of sulfone-bridging, lower swelling ability, and a high proportion of a dense polymer fraction in the swollen material are found in the resin obtained with chlorosulfonic acid. As a matter of fact, Cross Polarization Magic Angle Spinning Nuclear Magnetic Resonance (CP-MAS 13C-NMR), elemental analysis, and ion exchange capacity, show that oleum and chlorosulfonic acid produced resins with remarkably smaller pores and lower swollen gel volume in polar solvents, with respect to concentrated sulfuric acid.

Reducing Anomalous Hysteresis in Perovskite Solar Cells by Suppressing the Interfacial Ferroelectric Order.

Despite the booming research in organometal halide perovskite solar cells (PSCs) of recent years, considerable roadblocks remain for their large-scale deployment, ranging from undesirable current-voltage hysteresis to inferior device stability. Among various plausible origins of hysteresis, interfacial ferroelectricity is particularly intriguing and warrants a close scrutiny. Here, we examine interfacial ferroelectricity in MAPbI3 (FAPbI3)/TiO2 and MAPbI3/phenyl-C61-butyric-acid-methyl-ester (PCBM) heterostructures and explore the correlations between the interfacial ferroelectricity and the hysteresis from the perspective of nonadiabatic electronic dynamics. It is found that the ferroelectric order develops at the MAPbI3/TiO2 interface owing to the interaction between the polar MA ions and TiO2. The polarization switching of the MA ions under an applied gate field would drastically result in different rates in interfacial photoelectron injection and electron-hole recombination, contributing to the undesirable hysteresis. In sharp contrast, ferroelectricity is suppressed at the FAPbI3/TiO2 and MAPbI3/PCBM interfaces, thanks to elimination of the interfacial electric field between perovskite and TiO2 via substitution of strong polar MA (dipole moment: 2.29 debye) by weak polar FA ions (dipole moment: 0.29 debye) and interface passivation, leading to consistent interfacial electronic dynamics and the absence of hysteresis. The present work sheds light on the physical cause for hysteresis and points to the direction to which the hysteresis could be mitigated in PSCs.

Ion Pairing and Redissociaton in Low-Permittivity Electrolytes for Multivalent Battery Applications.

Detailed speciation of electrolytes as a function of chemical system and concentration provides the foundation for understanding bulk transport as well as possible decomposition mechanisms. In particular, multivalent electrolytes have shown a strong coupling between anodic stability and solvation structure. Furthermore, solvents that are found to exhibit reasonable stability against alkaline-earth metals generally exhibit low permittivity, which typically increases the complexity of the electrolyte species. To improve our understanding of ionic population and associated transport in these important classes of electrolytes, the speciation of Mg(TFSI)2 in monoglyme and diglyme systems is studied via a multiscale thermodynamic model using first-principles calculations for ion association and molecular dynamics simulations for dielectric properties. The results are then compared to Raman and dielectric relaxation spectroscopies, which independently confirm the modeling insights. We find that the significant presence of free ions in the low-permittivity glymes in the concentration range from 0.02 to 0.6 M is well-explained by the low-permittivity redissociation hypothesis. Here, salt speciation is largely dictated by long-range electrostatics, which includes permittivity increases due to polar contact ion pairs. The present results suggest that other low-permittivity multivalent electrolytes may also reach high conductivities as a result of redissociation.

Dipole-phonon quantum logic with alkaline-earth monoxide and monosulfide cations.

Dipole-phonon quantum logic (DPQL) leverages the interaction between polar molecular ions and the motional modes of a trapped-ion Coulomb crystal to provide a potentially scalable route to quantum information science. Here, we study a class of candidate molecular ions for DPQL, the cationic alkaline-earth monoxides and monosulfides, which possess suitable structure for DPQL and can be produced in existing atomic ion experiments with little additional complexity. We present calculations of DPQL operations for one of these molecules, CaO+, and discuss progress towards experimental realization. We also further develop the theory of DPQL to include state preparation and measurement and entanglement of multiple molecular ions.

Structure and Dynamics of an Ionic Liquid Mixture Film Confined by Mica

In a recent article ( J. Phys. Chem. C 2019, 123, 4914−4925) we studied using molecular dynamics simulations the structure of an ionic liquid (IL) mixture comprised of 1-methyl-3-octylimidazolium octylsulfate and 1-ethyl-3-methylimidazolium ethylsulfate confined by vacuum interfaces. At these interfaces, the mixture formed an apolar blocking layer concealing the smaller and more polar ions to the interior of the liquid phase. In the current work, and for the same IL mixture, we study the case of confinement between (001) mica surfaces, where the solid provides a flat and polar ionic interface. Our focus is twofold; first, we want to understand the structural and dynamical behaviors of the IL mixture at the boundary where the confining interface is highly polar, and second we want to establish how far away from the interface liquid behavior is recovered. This last point is particularly important in light of puzzling recent experimental results regarding the behavior of ILs and solutes dissolved in them und...

Effect of thermal ageing on space charge in ethylene propylene rubber at DC voltage

To understand the space charge characteristics of ethylene propylene rubber (EPR) used in MV/HV power cables under thermal stress, the space charge profile is measured by the pulsed electro-acoustic method under 20 kV/mm at 120 and 160 °C. The complex permittivity and physicochemical properties at the different ageing stages are measured and analyzed for an understanding of the effects of thermal ageing on space charge characteristics. The trap properties of EPR during thermal ageing is calculated and analyzed based on the space charge decay model. The results show that both the ageing time and temperature can affect the space charge characteristics of EPR The space charge characteristics of EPR can be ascribed to the trapping sites caused by the complex chemical and physical structures during thermal ageing. Under the thermal oxygen process, the polar groups and ions increase because of the EPR molecular chain breakages, and the charge injection from the electrodes increases. Based on the decay model of space charge and isothermal decay current theory, the distribution of trap levels in EPR at different ageing stages is obtained. The trap distribution under different ageing process can be explained by the theory of trap filling.

Effect of thermal ageing on space charge in ethylene propylene rubber at DC voltage

To understand the space charge characteristics of ethylene propylene rubber (EPR) used in MV/HV power cables under thermal stress, the space charge profile is measured by the pulsed electro-acoustic method under 20 kV/mm at 120 and 160 °C. The complex permittivity and physicochemical properties at the different ageing stages are measured and analyzed for an understanding of the effects of thermal ageing on space charge characteristics. The trap properties of EPR during thermal ageing is calculated and analyzed based on the space charge decay model. The results show that both the ageing time and temperature can affect the space charge characteristics of EPR The space charge characteristics of EPR can be ascribed to the trapping sites caused by the complex chemical and physical structures during thermal ageing. Under the thermal oxygen process, the polar groups and ions increase because of the EPR molecular chain breakages, and the charge injection from the electrodes increases. Based on the decay model of space charge and isothermal decay current theory, the distribution of trap levels in EPR at different ageing stages is obtained. The trap distribution under different ageing process can be explained by the theory of trap filling.

Hepatic Metabolomic Analysis in Mice Fed a High Fat Diet with Watermelon and Watermelon Byproducts Shows Improved Lipid Metabolism and Reduction of Chronic Inflammation (P06-023-19)

ObjectivesWatermelon is a nutrient-dense fruit shown previously to produce health benefits, particularly regarding blood pressure regulation. We tested the hypothesis that intake of whole watermelon flesh and value-added watermelon components would improve metabolic conditions in C57BL/6 J male mice fed a high-fat, high-sucrose diet modeling an obesogenic Western diet (HF). We further hypothesize that metabolomic profiling will show changes in relative levels of compounds related to lipid and glucose metabolism, and chronic inflammation. MethodsIn a prior study (Becraft et al., 2018), groups of mice (n = 8) were provided either low-fat diet (LF, 10% kcal fat), high-fat diet (HF, 45% kcal fat), HF plus Watermelon Skin (HF + WS), HF plus Watermelon Rind (HF + WR), or HF plus Watermelon Flesh (HF + WF) for 10 weeks. Watermelon flesh was provided at 10% of total energy and skin and rind were added at ∼ 0.2% (w/w) of diet. After ten weeks, animals were euthanized, and liver tissue saved for metabolomic analysis. Liver tissue samples were homogenized, and an identical mass equivalent of liver was subjected to methanol extraction and split into aliquots for analysis by ultrahigh performance liquid chromatography/mass spectrometry in the positive, negative or polar ion mode. There were 709 biochemicals identified and analyzed between groups. Welch’s 2-sample t-test was performed with ArrayStudio (Omicsoft) or R software on log transformed data to compare data between experimental groups. Estimate of the false discovery rate (Q value) was calculated and Q ;< 0.05 used as an indication of high confidence in a result. ResultsPrincipal component analysis showed segregation of groups along three different components, representing 24.8%, 19.4%, and 9.0% of the variation. Profound differences were found in LF vs. HF liver tissue. Compared to HF-fed mice, mice fed WF showed reduced levels of bile acids and pro-inflammatory compounds 12-HETE, 15, HETE, and PGF2 (all P < 0.05) in the liver. ConclusionsIn mice consuming a high-fat western style diet, regular intake of watermelon flesh, and fiber-rich products made from rind and skin all improved metabolism as evidenced by metabolomic analysis of liver tissue. Most notably were reductions in pro-inflammatory compounds including HETEs and Prostaglandin F2. Funding SourcesNational Watermelon Promotion Board.

Time-fractional effect on dust-acoustic double-layer waves in four-component dusty plasma

Abstract The Gardener equation (GE) is resulting by using reductive perturbation technique (RPT) for a system of dusty plasma of opposite polarity and kappa-distributed electrons and ion. Also, the time fractional (TF) Gardenr's equation obtained by Euler-Lagrange equation (ELe). It has been discover that the effect of the ions (electrons) kappa parameter ki(ke) and the ratio between temperatures of positive dust grains σ and that for ions studied, where the effect of ions kappa parameter k i on the amplitude and steepness of the double layers is more effective that the effect of both electrons kappa parameter k e and the ratio between temperatures of positive dust grains σ . The dependence of the envelope wave on the TF parameter α studied. The current inspection is founded in Jupiter, Cometary tails, and Earth's mesosphere.

Zeolite Clinoptilolite: Therapeutic Virtues of an Ancient Mineral.

Zeolites are porous minerals with high absorbency and ion-exchange capacity. Their molecular structure is a dense network of AlO4 and SiO4 that generates cavities where water and other polar molecules or ions are inserted/exchanged. Even though there are several synthetic or natural occurring species of zeolites, the most widespread and studied is the naturally occurring zeolite clinoptilolite (ZC). ZC is an excellent detoxifying, antioxidant and anti-inflammatory agent. As a result, it is been used in many industrial applications ranging from environmental remediation to oral applications/supplementation in vivo in humans as food supplements or medical devices. Moreover, the modification as micronization of ZC (M-ZC) or tribomechanically activated zeolite clinoptilolite (TMAZ) or furthermore as double tribomechanically activated zeolite clinoptilolite (PMA-ZC) allows improving its benefits in preclinical and clinical models. Despite its extensive use, many underlying action mechanisms of ZC in its natural or modified forms are still unclear, especially in humans. The main aim of this review is to shed light on the geochemical aspects and therapeutic potentials of ZC with a vision of endorsing further preclinical and clinical research on zeolites, in specific on the ZC and its modified forms as a potential agent for promoting human brain health and overall well-being.

Effect of polarity on beam and plasma target formation in a dense plasma focus

Dense plasma focus (DPF) devices are conventionally operated with a polarity such that the inner electrode (IE) is the anode. It has been found that interchanging the polarity of the electrodes (i.e., IE as the cathode) can cause an order of magnitude decrease in the neutron yield. This polarity riddle has previously been studied empirically through several experiments and is yet not well understood. We have performed kinetic simulations using the particle-in-cell modeling to investigate the problem. This is the first time that both polarities have been studied with simulations in great detail. In our simulations, we have modeled the entire beam and plasma target formation processes, but we did not consider differences in break-down conditions caused by the two polarities. We have found that when using reverse polarity ions are still accelerated and, in fact, attain similar energy spectra as in the standard polarity case. The difference is that the fields are flipped and thus ions are accelerated in the opposite direction. So, in the reverse polarity case, the majority of the “plasma target” (formed by the imploding plasma) is in the opposite direction of the beam, and thus, the beam hits the IE and produces few neutrons. With a better inner electrode configuration, reverse polarity is able to create a high-quality ion beam as well as a high-density target. Both can be comparable to that generated by standard polarity. Furthermore, we will show that it is easier to add an additional solid catcher target to a DPF device with reverse polarity, potentially enabling it to generate more neutrons than standard polarity.

Dual Polarity Ion Confinement and Mobility Separations.

Here, we present simulations and describe the initial implementation of a device capable of performing simultaneous ion mobility (IM) separations of positive and negative ions based upon the structures for lossless ion manipulations (SLIM). To achieve dual polarity ion confinement, the DC fields used for lateral confinement in previous SLIM were replaced with RF fields. Concurrent ion transport and mobility separation in the SLIM device are shown possible due to the nature of the traveling wave (TW) voltage profile which has potential minima at opposite sides of the wave for each ion polarity. We explored the potential for performing simultaneous IM separations of cations and anions over the same SLIM path and the impacts on the achievable IM resolution and resolving power. Initial results suggest comparable IM performance with previous single-polarity SLIM separations can be achieved. We also used ion trajectory simulations to investigate the capability to manipulate the spatial distributions of ion populations based on their polarities by biasing the RF fields and TW potentials on each SLIM surface so as to limit the interactions between opposite polarity ions. Graphical Abstract.

The Crab Pulsar: Origin of the Crab Nebula’s Radio Pairs

Abstract Previously, we constructed a model—essentially a plausibility argument—in which the Crab Pulsar produces a spatially separated ion dominated and pair plasma dominated, magnetically striped relativistic wind, with the ion wind’s kinetic energy and electromagnetic Poynting fluxes being comparable. In this paper, the polar cap ion–photon pair production of that model is replaced with pair production by ion curvature synchrotron photons. The first primary ion curvature photons, and, contrary to conventional wisdom, also the first primary electron curvature photons, do not immediately convert into pairs. The primary beam particles continue to accelerate, and the actual photons that convert into pairs, which then short out the parallel electric field and terminate the acceleration, are produced by the further accelerated, higher energy particles. Simple estimates of the ensuing pair production cascade give pair multiplicities—the number of pairs per primary beam particle—of M ± ≈ 6–8 × 104, comparable to standard calculations, but much less than the 3 × 106 value deduced by Rees and Gunn in order to sustain the Crab Nebula’s N ± ≈ 1051 radio-emitting pairs against adiabatic expansion energy losses. Using a simple spin-down evolution model for the pulsar’s rotation frequency, the time-integrated pair cascade production driven by the primary ion beam can produce the N ± ≈ 1051 radio pairs, whereas the primary electron beam produces about an order of magnitude fewer pairs.

Investigation of electrospray for a capillary electrophoresis-mass spectrometry interface in reverse polarity and negative ion mode.

Capillary zone electrophoresis (CZE) paired with mass spectrometry (MS) is a powerful analytical technique for examining mixtures of ionic analytes such as glycosaminoglycans. This study examines the mechanics of the electrospray process for a sheath flow CZE-MS interface under reverse polarity negative ionization conditions. Liquid flow in a sheath flow nano-electrospray CZE-MS interface is driven by two mechanisms, electroosmotic flow and electrospray nebulization. The contribution of these two processes to the overall flow of solution to the electrospray tip is influenced by the surface coatings of the sheath flow emitter tip and by the solvent composition. We have investigated the application of this interface to the reverse polarity separation of glycosaminoglycans and find that the role of electroosmotic flow is far less than has been reported previously, and the electrospray process itself is the largest contributor to the flow of the sheath liquid.

Determination of 27 fragrances in cosmetics and perfume raw materials by gas chromatography-mass spectrometry

A chromatographic separation method for 27 fragrances in cosmetics and perfume raw materials was developed using gas chromatography-mass spectrometry (GC-MS). A weak polar capillary column and electron impact ion source were used in the GC-MS analysis, with methanol as the extraction solvent. The limits of detection were 1.2, 15, and 15 mg/kg for musk xylene, hydroxycitronellal, and hydroxyisohexyl-3-cyclohexene carboxaldehyde, respectively, and 3.0 mg/kg for the other 24 fragrances. The calibration line of the 27 fragrances presented a good relationship with correlation coefficients ≥ 0.996. At three spiked concentration levels, the relative standard deviations were <10% and the spiked recoveries were in the ranges of 73.3%-76.1% for musk xylene and 81.5%-118% for the other fragrances. Based on these determinations, one or more fragrance ingredients were detected in 69 perfume raw materials and cosmetics, the labels of which indicated that they contained fragrances. This method can be used to determine 27 fragrances in cosmetic and perfume raw materials.