Ionic Polarization Research Articles

Dicarbocyanine-based organic humidity sensors

The utilization of organic dicarbocyanine dye-conjugated molecules, specifically 1,1′-diethyl-4,4′-dicarbocyanine iodide (DDCI-4), as the sensing film in capacitive-type humidity sensors has been demonstrated. The structural, morphological, and wettability characteristics of the sensing films as well as the performance of the electrode gaps of the devices were analyzed. Aluminum (Al)/DDCI-4/Al capacitive humidity sensors were fabricated using solution-processed spin coating techniques in a planar geometry. In this study, a surface profiler was used to measure the size of electrode gaps, which were 94.87 ± 1.20 µm, 391.00 ± 1.53 µm, 902.00 ± 2.08 µm, and 1906.67 ± 3.33 µm. Compared to those with larger gaps (391 µm, 902 µm, and 1907 µm), the device with the smallest gap measured 45 ± 9.1 fF/%RH with the highest sensitivity. In addition, the hysteresis with response and recovery performances has been studied, revealing the lowest values of 0.31%, 6 s, and 9 s, respectively. It is anticipated that the 1,1′-diethyl-4,4′-dicarbocyanine iodide's electronic, ionic, and dipole polarizations are responsible for the excellent performance of dye-based organic humidity sensors.

Fine-structure constant and hysteresis regimes in the giant squid propagating action potential.

We present a phase space based phenomenological theory for the steady propagation of the action potential using the Rosenthal-Bezanilla experimental data. Time derivatives of giant squid action potential, its velocity of propagation, the radius of the axon and its capacitance, and the resistivity of axoplasm, yield the total ionic, capacitive, and membrane currents of the charge conserving cable equation. Evidence is presented that the sodium channels lattice has a polarization flip at the inception of the action potential and the corresponding flip reversal at the peak of the action potential while traversing a ferroelectric hysteresis loop. The polarization flip at the inception of the action potential is followed by capacitive polarization current known as gating current. The polarization flip at the peak of the action potential is preceded by a small sodium polarization current associated with sodium current inactivation. Ionic currents and sodium polarization ionic currentsare taken to have the familiar structure, as the product of maximum conductance, driving force, and fraction of open channels. Fractions of open channels are fitted in the lab frame by modified Avrami equations seeded with the value of the fine-structure constant α = 0.0072973... . The existence of sodium channels domains with two different symmetries, albeit only one being stable in squid axon, suggests the possibility of neurons with at least 2 stable states, the necessary condition for storage and retrieval of memories. It is expected that presented results will provide the framework for further analysis of thermodynamic phase changing behavior, the role of quantum mechanics in the flow of ions trough ionic channels and in particular the role of ferroelectric sodium channels lattice behavior in storage and retrieval of memories and nerve excitability.

Nb-Doped TiO2 with Outstanding Na/Mg-Ion Battery Performance.

The group "beyond Li-ion" batteries (Na/Mg-ion batteries) have the advantages of abundant reserves and high theoretical specific capacity. However, the sluggish kinetics resulting from large ion radius (Na+) and polarity (Mg2+) seriously limit the battery performance. Herein, we prepared Nb-doped anatase TiO2 with Ti vacancies (Nb-TiO2) through a simple solvothermal and subsequent calcination process. The Nb doping widens the channels for metal ion diffusion, and the cationic vacancies can act as ion storage sites and improve the electrode conductivity. Thus, Nb-TiO2 exhibits improved performance for rechargeable Na/Mg-ion batteries.

High-Q×f value and temperature stable MgZrTa2O8 ceramics by Li heterovalent substitution

The Mg1-xLixZrTa2O8-x/2 (x = 0–0.07) ceramics were fabricated to investigate the effects of Li+ heterovalent substitution for Mg2+. The site occupancy and existence of the Li+ were examined based on Vienna Ab-initio Simulation Package (VASP) and X-ray photoelectron spectroscopy (XPS), respectively. Single phase solid solution with wolframite structure was identified in the whole region. Li+ substitution reduced the densification temperature from 1475 °C to 1400 °C. Notably, the Q×f exhibited an obvious increase by up to 74 % from 41,844 GHz at x = 0–72,782 GHz at x = 0.05. The Q×f for x < 0.01 was largely dependent on the intrinsic loss originating from packing fraction, while as 0.01 ≤ x ≤ 0.05, it was dominated by extrinsic factors, especially the oxygen vacancy concentration. The corresponding dielectric constant εr decreased in term of ionic polarizability. The variations of resonant frequency temperature coefficient τf were explained from the views of [TaO6] oxygen octahedral distortion and bond energy. A near-zero τf was obtained for x = 0.05 composition, accompanied by εr = 11.97, Q×f= 72,782 GH at 1450 °C. Li substitution was effective and inexpensive for MgZrTa2O8 ceramic to realize dielectric properties enhancement and densification temperature optimization simultaneously.

Evolution of the ionic polarization in multiple sequential ionization: General equations and an illustrative example

Modern free-electron lasers generate a highly intense polarized radiation which initiates a sequence of ionization and decay events. Their probability depends on the polarization of each involved state as a function of time. Its complete account is limited by the fact that a state can be formed in various ways. Here we present an equivalent of rate equations for population that completely accounts for polarization of radiation formulated in terms of statistical tensors. To illustrate our approach we theoretically consider the sequential photoionization of krypton by an intense extreme ultraviolet femtosecond pulse for photon energies below the $3d$-shell excitation threshold. The calculations of the ion yields, photoelectron spectra, and ionic polarization for various photon fluences are presented and the role of the polarization is discussed.

Identification of induced polarization of submarine hydrocarbons in marine controllable source electromagnetic exploration

The identification of hydrocarbons buried on the seafloor is highly dependent on geophysical exploration capabilities. Seismic exploration has been an important tool in providing information on submarine stratigraphy before offshore drilling, but it is a challenge to identify the nature and saturation of the fluid in the structure by seismic exploration. Of all the physical properties, electrical parameters are the most sensitive to the fluids in the reservoir and would be able to be combined with seismic data to improve the identification of hydrocarbons at depth. However, the marine controlled-source electromagnetic method usually only considers the effect of electromagnetic induction and ignores the induced polarization (IP) effects. The IP effects can occur in the stratum where the reservoir is located due to a variety of factors, so considering the IP effects will make the modeling more reasonable and thus give more accurate results when interpreting and processing the data. We have used the integral equation method for modeling, adopted the scattering and superposition methods to calculate the dyadic Green’s function required in the study, replaced the real resistivity with a complex resistivity that takes into account the IP effects, investigated the response patterns of different ion polarization models, and analyzed the influence patterns of various model parameters. These investigations will provide important contributions to the study of submarine hydrocarbon detection. The field data also show the amplitude, and phase response results of polarizability show that it gradually increases from the offset.

Mechanism of ionic polarizability, bond valence, and crystal structure on the microwave dielectric properties of disordered Li10MTi13O32 (M = Zn, Mg) spinels

The influence mechanism of the microwave dielectric properties of disordered spinels Li10MTi13O32 (M = Zn, Mg) was investigated via structural refinement, ionic polarizability, bond valence, P–V–L theory, Raman spectroscopy, and DC conductivity.

Control of electronic polarization via charge ordering and electron transfer: electronic ferroelectrics and electronic pyroelectrics.

Ferroelectric, pyroelectric, and piezoelectric compounds whose electric polarization properties can be controlled by external stimuli such as electric field, temperature, and pressure have various applications, including ferroelectric memory materials, sensors, and thermal energy-conversion devices. Numerous polarization switching compounds, particularly molecular ferroelectrics and pyroelectrics, have been developed. In these materials, the polarization switching usually proceeds via ion displacement and reorientation of polar molecules, which are responsible for the change in ionic polarization and orientational polarization, respectively. Recently, the development of electronic ferroelectrics, in which the mechanism of polarization change is charge ordering and electron transfer, has attracted great attention. In this article, representative examples of electronic ferroelectrics are summarized, including (TMTTF)2X (TMTTF = tetramethyl-tetrathiafulvalene, X = anion), α-(BEDT-TTF)2I3 (BEDT-TTF = bis(ethylenedithio)-tetrathiafulvalene), TTF-CA (TTF = tetrathiafulvalene, CA = p-chloranil), and [(n-C3H7)4N][FeIIIFeII(dto)3] (dto = 1,2-dithiooxalate = C2O2S2). Furthermore, polarization switching materials using directional electron transfer in nonferroelectrics, the so-called electronic pyroelectrics, such as [(Cr(SS-cth))(Co(RR-cth))(μ-dhbq)](PF6)3 (dhbq = deprotonated 2,5-dihydroxy-1,4-benzoquinone, cth = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraaza-cyclotetradecane), are introduced. Future prospects are also discussed, particularly the development of new properties in polarization switching through the manipulation of electronic polarization in electronic ferroelectrics and electronic pyroelectrics by taking advantage of the inherent properties of electrons.

Wetting and spreading phenomena in liquid bismuth-alkali halide systems

This investigation is devoted to the study of the features of wetting phenomena in high temperature systems that are promising as environments for processing and disposal of man-made and radioactive wastes. New data on the phase wetting transition in two-phase liquid media have been obtained by analyzing the values of the adhesion of salt melts to liquid metals. The present study is focused on the systems composed of molten alkali halides and liquid bismuth. Their adhesion was calculated using experimental data on the surface tension of metals and salts, as well as the interfacial tension between metals and salts. A regular change in the adhesion work is illustrated depending on the temperature, electrical potential and nature of the contact phases. The transition phenomenon from incomplete wetting to full wetting has been established. It is shown that this transition is facilitated by an increase in temperature, a potential jump in the phase contact plane, and the polarizability of salt phase ions. The potential dependence of the adhesion work near the wetting transition point is described by a power equation with a critical index equal to 1.1.

Effect of air bubbling on electroless Pd plating for the practical application of hydrogen selective membranes.

In this study, an air bubbling electroless plating (ELP) method was newly developed for the production of Pd composite membranes. The air bubble ELP alleviated the concentration polarization of Pd ions, making it possible to achieve a plating yield of 99.9% in 1 h and form very fine Pd grains with a uniform layer of ∼4.7 μm. A membrane with a diameter of 25.4 mm and a length of 450 mm was produced by the air bubbling ELP, achieving a hydrogen permeation flux of 4.0 × 10-1 mol m-2 s-1 and selectivity of ∼10 000 at 723 K with a pressure difference of 100 kPa. To confirm the reproducibility, six membranes were produced by the same method and assembled in a membrane reactor module to produce high-purity hydrogen by ammonia decomposition. Hydrogen permeation flux and selectivity of the six membranes at 723 K with a pressure difference of 100 kPa were 3.6 × 10-1 mol m-2 s-1 and ∼8900, respectively. An ammonia decomposition test with an ammonia feed rate of 12 000 mL min-1 showed that the membrane reactor produced hydrogen with >99.999% purity and a production rate of 1.01 Nm3 h-1 at 748 K with a retentate stream gauge pressure of 150 kPa and a permeation stream vacuum of -10 kPa. The ammonia decomposition tests confirmed that the newly developed air bubbling ELP method affords several advantages, such as rapid production, high ELP efficiency, reproducibility, and practical applicability.

Ionic and electronic polarization effects in horizontal hybrid perovskite device structures close to equilibrium.

The electrical response of hybrid perovskite devices carries a significant signature from mobile ionic defects, pointing to both opportunities and threats when it comes to functionality, performance and stability of these devices. Despite its importance, the interpretation of polarization effects due to the mixed ionic-electronic conducting nature of these materials and the quantification of their ionic conductivities still poses conceptual and practical challenges, even for the equilibrium situation. In this study, we address these questions and investigate the electrical response of horizontal devices based on methylammonium lead iodide (MAPI) close to equilibrium conditions. We discuss the interpretation of DC polarization and impedance spectroscopy measurements in the dark, based on calculated and fitted impedance spectra obtained using equivalent circuit models that account for the mixed conductivity of the perovskite and for the effect of device geometry. Our results show that, for horizontal structures with a gap width between the metal electrodes in the order of tens of microns, the polarization behavior of MAPI is well described by the charging of the mixed conductor/metal interface, suggesting a Debye length in the perovskite close to 1 nm. We highlight a signature in the impedance response at intermediate frequencies, which we assign to ionic diffusion in the plane parallel to the MAPI/contact interface. By comparing the experimental impedance results with calculated spectra for different circuit models, we discuss the potential role of multiple mobile ionic species and rule out a significant contribution from iodine exchange with the gas phase in the electrical response of MAPI close to equilibrium. This study helps to clarify the measurement and interpretation of mixed conductivity and polarization effects in hybrid perovskites with immediate relevance to the characterization and development of transistors, memristors and solar cells based on this class of materials as well as other mixed conductors.

Controversial Issues of Hydrocarbon Field Formation and the Role of Geomagnetic Fields

This review paper presents controversial issues on the formation of hydrocarbon deposits. We look into the geological contradictions of the abiogenic and biogenic theories of petroleum origin, indicating the connection between hydrocarbon deposits and disjunctive dislocations, as well as present disputes about the geological period over which hydrocarbon deposits have been formed. We further overviewed the radical chain mechanism of hydrocarbon generation from organic matter as proposed by Prof. Nesterov. It is noted that the petroleum generation process in reservoir conditions occurs almost instantly in the presence of discrete geomagnetic fields and does not require a long geological time. This is explained by spin magnetic effects (spin catalysis, magnetic isotope properties). We briefly highlight the effect of magnetic fields on chemical reactions involving organic compounds and the use of magnetic fields to enhance oil recovery. We also present the leading causes of discrete magnetic fields in the sedimentary cover: Earth’s geomagnetic reversals, generation of ferromagnetic minerals in oil deposits, electromechanical effects of rock friction near faults, and intermixing of reservoir waters with different mineralization (spontaneous ion polarization). Based on the material reported, we conclude that the radical chain mechanism of petroleum generation processes explains some contradictions of the abiogenic and biogenic theories of petroleum origin. Elaborating this research area has excellent prospects for developing new criteria for hydrocarbon prospecting and devising innovative methods to enhance the oil recovery for shale oil production.

Aggregation of Multimodal ICE-MS Data into Joint Classifier Increases Quality of Brain Cancer Tissue Classification

Mass spectrometry fingerprinting combined with multidimensional data analysis has been proposed in surgery to determine if a biopsy sample is a tumor. In the specific case of brain tumors, it is complicated to obtain control samples, leading to model overfitting due to unbalanced sample cohorts. Usually, classifiers are trained using a single measurement regime, most notably single ion polarity, but mass range and spectral resolution could also be varied. It is known that lipid groups differ significantly in their ability to produce positive or negative ions; hence, using only one polarity significantly restricts the chemical space available for sample discrimination purposes. In this work, we have developed an approach employing mass spectrometry data obtained by eight different regimes of measurement simultaneously. Regime-specific classifiers are trained, then a mixture of experts techniques based on voting or mean probability is used to aggregate predictions of all trained classifiers and assign a class to the whole sample. The aggregated classifiers have shown a much better performance than any of the single-regime classifiers and help significantly reduce the effect of an unbalanced dataset without any augmentation.

Molten salt assisted Co1−xAgxMoO4 with lattice Ag doping and oxygen vacancy for stable water oxidation

Spinel type oxides including CoMoO4 are promising catalysts for water electrolysis. However, MoO42− is easy to dissolve during oxygen evolution reaction (OER), resulting in the poor performance. The lattice modulation of CoMoO4 may be an effective strategy for better activity and stability. In our work, molten salt method has been adopted to realize the incorporation of Ag into the lattice surface of CoMoO4 nanorods. The physical characterizations show that Ag is uniformly distributed in the surface lattice of optimized Co1−xAgxMoO4. Lattice Ag doping stabilizes the structure of Co1−xAgxMoO4 by adjusting the electron distribution state to form a high-valence Co. Moreover, the incorporation of low-valence Ag+ causes the Co1−xAgxMoO4 to produce more oxygen vacancies, which reduces the charge transfer resistance by about 15 times compared to CoMoO4. The electrochemical measurements demonstrate that Co1−xAgxMoO4 exhibits a lower OER overpotential (330 mV) at 10 mA cm−2 and the 2.7 longer time than CoMoO4 during chronopotentiometry test. DFT calculation reveals that Ag doping with ion polarization optimizes the electron distribution of Co-O and enhances the covalency of Mo-O to slow down the solubility of Co1−xAgxMoO4. This work shows that lattice doping of metal ions may be a great choice for excellent electrocatalysts for OER.

Continuous Submicron Particle Separation Via Vortex-Enhanced Ionic Concentration Polarization: A Numerical Investigation.

Separation and isolation of suspended submicron particles is fundamental to a wide range of applications, including desalination, chemical processing, and medical diagnostics. Ion concentration polarization (ICP), an electrokinetic phenomenon in micro-nano interfaces, has gained attention due to its unique ability to manipulate molecules or particles in suspension and solution. Less well understood, though, is the ability of this phenomenon to generate circulatory fluid flow, and how this enables and enhances continuous particle capture. Here, we perform a comprehensive study of a low-voltage ICP, demonstrating a new electrokinetic method for extracting submicron particles via flow-enhanced particle redirection. To do so, a 2D-FEM model solves the Poisson-Nernst-Planck equation coupled with the Navier-Stokes and continuity equations. Four distinct operational modes (Allowed, Blocked, Captured, and Dodged) were recognized as a function of the particle's charges and sizes, resulting in the capture or release from ICP-induced vortices, with the critical particle dimensions determined by appropriately tuning inlet flow rates (200-800 [µm/s]) and applied voltages (0-2.5 [V]). It is found that vortices are generated above a non-dimensional ICP-induced velocity of U*=1, which represents an equilibrium between ICP velocity and lateral flow velocity. It was also found that in the case of multi-target separation, the surface charge of the particle, rather than a particle's size, is the primary determinant of particle trajectory. These findings contribute to a better understanding of ICP-based particle separation and isolation, as well as laying the foundations for the rational design and optimization of ICP-based sorting systems.

The effect of Bi2O3/PbO substitution on physical, optical, structural, and gamma shielding properties of boro-tellurite glasses

Boro-tellurite glasses with molar compositions 60TeO2–20B2O3-(20-x)Bi2O3-xPbO, where x = 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 mol% were fabricated using a standard melt quenching technique and studied in term of their physical, optical, structural and gamma shielding properties. As PbO concentration increases from 0 to 10 mol% (Bi2O3 decreases), the density and molar volume of the present samples decrease from 6.08 to 5.93 gr/cm3 and 33.37 to 30.27 cm3/mol, respectively. The optical packing density increases from 71.91 to 72.67% as PbO is added to the network to substitute Bi2O3. With the increase of PbO concentration, the refractive index, molar refractivity, and ionic polarizability decrease from 1.9137 to 1.8306, 18.531 to 16.884 cm3, and 7.3534 to 6.7000 Å3, respectively. The percentage of [TeO3] (tp) and [TeO3+1] polyhedra in the glass network increase with the rise of PbO concentration. The gamma radiation shielding features were analyzed theoretically using Phy-X PSD software with photon energies varied between 0.015 and 15 MeV. For all glasses, the highest linear attenuation coefficient (LAC) values are observed at 0.015 MeV while the lowest values are observed around 5 MeV, a turning point at which pair production starts to dominate the gamma photon-electron interaction. At all photon energies, the LAC values decrease with the increase in PbO concentration (the decrease in Bi2O3). The LAC values at 0.015 MeV vary from 413.2183 to 12.4962 cm−1. At low photon energies (0.015–0.04 MeV), this compositional dependence is high. Above 0.04 MeV, this dependence is low. This LAC result suggests that adding Bi2O3 to the glasses is favorable for gamma shielding material as compared to PbO.

Advancement in Soft Iontronic Resistive Memory Devices and Their Application for Neuromorphic Computing

The aqueous electrolyte can be a deformable and stretchable liquid material for iontronic resistive memory devices. An aqueous medium makes a device closer to the brain‐like system with the movement of ions. This review paper proposes advances in liquid resistive memories and neuromorphic computing behavior to emulate electronic synapses. Primarily, the aqueous iontronic resistive memories can be used to study electrode and active layer materials and different device structures. Hence, herein, a timely and comprehensive study of these devices using ionic liquids, hydrogels, salt solutions, and soft electrodes to classify the device mechanism is presented. The filament formation is discussed in detail based on ion concentration polarization, electrode metallization, and movements of ions and charged molecules, which result in the formation of the metal dendrite. To manufacture a higher‐performance memory, device parameters should be optimized based on aqueous electrolytes, electrode materials, and other device design parameters. Aqueous electrolytes have smooth neurotransmission ability to fabricate brain‐inspired resistive memories with stable performance and device repeatability with smooth ion transmission. Aqueous electrode materials can be reliable for neural interface activities to compute electronic synapsis with electrical and chemical properties to ensure device reliability for a longer time period.

Effect of Local Structural Distortions on Antiferroelectric-Ferroelectric Phase Transition in Dilute Solid Solutions of KxNa1-xNbO3.

The fundamental principles that govern antiferroelectric (AFE)-ferroelectric (FE) transitions are not well understood for many solid solutions of perovskite compounds. For example, crystal chemical considerations based on the average Goldschmidt tolerance factor or ionic polarizability do not precisely predict the boundary between the AFE and FE phases in dilute solid solutions of alkali niobates, such as KxNa1-xNbO3 (x ≤ 0.02). Here, based on detailed structural analysis from neutron total scattering experiments, we provide insights about how the relative local distortions around the A- and B-sites of the ABO3 perovskite structure affect the AFE/FE order of the average crystallographic phases in KxNa1-xNbO3. We show that a higher (lower) ratio of B-site-centered distortions over A-site-centered distortions drives transition toward a long-range FE (AFE) phase, which is based on a competition between the long-range polarizing field of the Nb-O dipoles and the disordering effect of local distortions around the A-site. Our study provides a predictive tool for designing complex solid-solution perovskites with tunable (anti)ferroelectric polarization properties, which can be of interest for various energy-related applications such as high-density energy storage and solid-state cooling.

The Lyotropic Nature of Halates: An Experimental Study

Unlike halides, where the kosmotropicity decreases from fluoride to iodide, the kosmotropic nature of halates apparently increases from chlorate to iodate, in spite of the lowering in the static ionic polarizability. In this paper, we present an experimental study that confirms the results of previous simulations. The lyotropic nature of aqueous solutions of sodium halates, i.e., NaClO3, NaBrO3, and NaIO3, is investigated through density, conductivity, viscosity, and refractive index measurements as a function of temperature and salt concentration. From the experimental data, we evaluate the activity coefficients and the salt polarizability and assess the anions' nature in terms of kosmotropicity/chaotropicity. The results clearly indicate that iodate behaves as a kosmotrope, while chlorate is a chaotrope, and bromate shows an intermediate nature. This experimental study confirms that, in the case of halates XO3-, the kosmotropic-chaotropic ranking reverses with respect to halides. We also discuss and revisit the role of the anion's polarizability in the interpretation of Hofmeister phenomena.

Structural distortion induced enhancement of magnetic and dielectric properties in Pr modified yttrium iron garnet films

Low saturation magnetization and low dielectric constant significantly limited the application of Yttrium iron garnet (Y3Fe5O12, YIG) film, which could be enhanced through structural distortion. In this work, Y3-xPrxFe5O12 (YPrxIG) films were fabricated using chemical solution deposition method. The substitution of Pr3+ for Y3+ was adopted to regulate the symmetry of its polyhedron to induce a structural distortion owing to a larger ion radius of Pr3+ than that of Y3+. YPr0.20IG film exhibited a higher saturation magnetization of 241.2 emu/cm3 than the pure YIG film owing to the enhanced super-exchange from the increased FeO–O-FeT bond angle. The dielectric constant of YPr0.20IG film increased to 22.4 at 12.4 GHz, which was the contribution of electron polarization and ion polarization of Fe2+. The band gap value of YPr0.20IG film was reduced to 2.80 eV. These could be physically clarified that the electrons between Fe2+ and Fe3+ turned to migrate from the valence band to the conduction band.