Redistribution Of Ions Research Articles

Ponderomotive redistribution of heavy ions along a magnetic field line

We set up the problem of ponderomotive separation and acceleration of ions with different charge-to-mass ratios under the influence of Alfvén waves, which constantly exist in the magnetosphere in the form of geomagnetic pulsations. Formulas for partial ponderomotive forces acting on light and heavy (metallic) ions are derived. In the quasi-hydrodynamic approximation, a system of equations is obtained which describes the distribution of ions along magnetic field lines in Earth’s magnetosphere. The Clarke number, which characterizes plasma metallicity, is found to be maximum at a minimum magnetic field on the field line along which the Alfvén wave propagates. This leads to the accumulation of heavy ions at the top of the field line at the point of its intersection with the magnetic equator. The theoretical conclusions agree with satellite measurements of the distribution of heavy ions along field lines in Earth’s magnetosphere.

Ion Redistribution Gel Electrolyte Dissipates Interfacial Turbulence for Aqueous Zinc‐Ion Batteries

AbstractAqueous zinc‐ion batteries (AZBs) degrade under a high current density due to the existence of interfacial turbulence with severe concentration polarization. Herein, an ion redistribution gel electrolyte is introduced to stabilize the electrode‐electrolyte interface by regulating the ion density gradient. Negatively charged carboxymethyl groups in carboxymethyl starch ether polymer (PCMS) electrolytes can preferentially regulate the ion concentration at the anode interface. The quasi‐solid PCMS gel electrolytes can dissipate the charge accumulation caused by ion concentration differences, which is beneficial for achieving excellent electrochemical stability at high current densities. As a result, the symmetric Zn cells with PCMS gel electrolyte can be cycled for more than 2000 h at a high current density of 40 mA cm−2. Furthermore, the Zn//I2 cell using PCMS gel electrolyte also sustained cycling for over 8000 cycles, and the pouch cell with PCMS gel electrolyte exhibited practical deformable applications in flexible devices. This work highlights an effective gel electrolyte approach for enhancing interfacial stability, potentially advancing the development of highly reversible AZBs.

Giant Bulk Photovoltaic Power Generation in 2D AgBiP2Se6 Crystals

AbstractWith the theoretical high power conversion efficiency (PCE) exceeding the thermodynamic Schockley–Queisser (S–Q) limit, the bulk photovoltaic (BPV) effect, which is manifested in acentric crystals across the entire visual spectrum, holds great potential for next‐generation light‐harvesting devices. Here the abnormally giant second harmonic generation (SHG) activity and BPV response in 2D AgBiP2Se6 crystals with broken inversion symmetry is demonstrated, which can be remarkably enhanced with the thickness downscaling. Based on the vertical device sandwiched with graphene electrodes, the wideband light absorption of 2D AgBiP2Se6 crystals with Eg of 1.49 eV enables giant BPV response in the entire visible spectrum, and efficient utilization of solar energy contributes to large short‐current (≈330 mA cm−2), high PCE (≈0.13%) and EQE (≈12.5%) under 532 nm light illumination. Furthermore, benefitting from the local ion redistribution driven by an in‐plane electric field, the BPV photocurrent generation is effectively enhanced 3 times, yielding an extremely high PCE of 0.18%, according high among the reported 2D acentric crystals. The study reintroduces AgBiP2Se6 to the 2D acentric crystal family and lays the groundwork to develop BPV devices for light‐harvesting applications.

Distribution and redistribution of salt ions in saline soils with shallow groundwater table

Saline water resources are more abundant than freshwater. Bringing these resources into sustainable, productive use will offer opportunities to reduce competition for freshwater resources, especially in arid and semi-arid areas where freshwater is scarce. Hence, the primary objective of this study was to elucidate the dynamics of salt ions in saline profiles of various soil types (sandy Clovelly and sandy loam Bainsvlei) under malt barley cultivation across 2 seasons where no leaching between the seasons took place. Results of this lysimeter study investigating increasing irrigation salinity (ECi) set at 1.5, 4.5, 6, 9, and 12 dSꞏm−1 over 2 seasons were used to explore ion dynamics of a saline environment. The lysimeter set-up included a saline constant (1.2 m) groundwater table with its salinity corresponding to ECi. Findings showed that ion concentrations are higher closer to the water source only in the Bainsvlei soil and remain variable in the Clovelly soil. Salt dynamics were more predictable in sandy loam soil than in sandy soil, making management of saline sandy soils far more challenging when leaching is not possible. Therefore, our hypothesis that the absence of leaching between seasons will lead to a differentiated progressive accumulation of salt ions in the soil profile, with variable effects on the soil depending on soil texture, was true. We conclude that the desalinized zone, which we determined to be at a depth of 600 mm, should be used to guide crop selection. Furthermore, in addition to the apparent provision for leaching of saline profiles, fertilization should target restoring ion balances, especially provisioning for calcium deficiencies. Both soils were prone to nutritional disorders, most especially calcium deficiency. Therefore, in addition to provision for leaching saline profiles, fertilization should target calcium provisioning for crop production in arid saline environments.

Charge Carrier Dynamics at the Perovskite Interface with Self-Assembled Monolayers.

Self-assembled monolayers (SAMs) deposited on the hole-collecting electrodes of p-i-n perovskite solar cells effectively replace bulky hole transporting layers. However, the mechanism by which monolayers control the electronic processes and how they depend on the properties of the monolayer molecules remain poorly understood. In this study, we developed a simplified perovskite solar cell imitator with blocked electron extraction to investigate the photocurrent dynamics between the perovskite and the hole-collecting ITO electrode. We investigated the photoluminescence and photovoltage dynamics under short laser pulse excitation and addressed the influence of bulky and monomolecular hole transport layers. Our findings reveal that the photovoltage dynamics is significantly affected by the properties of the transport and perovskite layers, which in turn depend on the methods of sample preparation and exploration. Photocurrent dynamics is determined by several processes, including charge carrier displacement in the local electric field, hole transport to ITO, trapping of holes in interface trap states, and electron-hole recombination at the interface. We propose a model that takes into account molecular dipole moments and their ionization potentials to partially explain the different influences of different monolayers on the hole extraction and interfacial recombination rates. Additionally, the photovoltage dynamics also strongly depends on the illumination of the sample and shows memory effects that persist over minutes and hours and are attributed to the redistribution of ions.

Prolonged Hyperactivity Elicits Massive and Persistent Chloride Ion Redistribution in Subsets of Cultured Hippocampal Dentate Granule Cells.

Chloride ions play a critical role in neuronal inhibition through the activity of chloride-permeable GABAA receptor channels. Ion transporters, chloride channels, and immobile ion species tightly regulate intracellular chloride concentrations. Several studies related to epilepsy suggest that chloride extrusion function may decrease in an activity-dependent manner. Consequently, it is crucial to investigate whether intense neuronal activity, as observed during status epilepticus, could lead to sustained increases in intracellular chloride levels in neurons, which in turn could contribute to epilepsy-associated hyperexcitability. This study utilized the chloride sensitive indicator (6-Methoxyquinolinio) acetic acid ethyl ester bromide (MQAE) combined with fluorescence lifetime imaging (FLIM) to examine whether application of the convulsant, pilocarpine, a muscarinic acetylcholine receptor agonist, could induce synchronous epileptiform activity and elevate intracellular chloride concentrations in hippocampal slice cultures. Using a Gaussian mixture model, we identified a multimodal distribution of intracellular chloride levels among neurons, with a significant subset of these cells exhibiting massive and prolonged (days) chloride accumulation. The combination of multicellular imaging and statistical analysis served as a powerful tool for studying the emergence of multiple, distinct populations of neurons in pathological conditions, in contrast to homogeneous populations evident under control conditions.

Reconfigurable van der Waals Ferroionic Barristor for Multifunctional Nanoelectronics

Abstract2D materials have been interested in recent years due to their unique properties and enormous potential in various fields. In particular, 2D ferroionics with both ferroelectricity and ionic conductivity shed light on new possibilities for van der Waals nanoelectronics. Here, supported by theoretical calculations and electrical characterizations, the reconfigurable van der Waals ferroionic barristor that can be used in multifunctional electronics including resistive devices and steep‐slope transistors is reported. Large modulation on the device properties is achieved by electrically driven migration and redistribution of mobile ions. The memory device shows an unprecedented long‐term stability with a switching ratio of ≈1010. Utilizing this ferroionic nature, 2D transistors able to beat the Boltzmann tyranny, with different gate configurations, are designed. The subthreshold swing (SS) exhibits sub‐60 mV per decade values over five decades of the drain current with a minimum of 12.1 mV per decade. This work paves the way for investigating the symbiotic relationship of ferroelectricity and ionic activities in van der Waals ferroionics and highlights their applications in advanced nanoelectronics.

Effect of gamma and neutron irradiations on the physical, magnetic and electrical properties of Ni–Cu–Cd nano-ferrites

The physical, magnetic and electrical properties variations for the sol-gel auto combustion synthesized Ni0.3Cu0.2Cd0.5Fe2O4 by gamma (γ) and neutron irradiations dose applications are studied in this research. The irradiation have been done through 2.0 × 1011 and 1.9 × 1012 cm−2s−1 per min fast neutron flux and γ rays from the research reactor of TRIGA MARK-II and 64 KCi cylindrical 60Co source respectively within room temperature. The rate of 1 Mrad and 3 Mrad dose is 1.067 Mrad/h. XRD results show greater intensities for the irradiation doses. Due to the redistribution of ions, changes in the lattice constant have been found by the irradiation through the results of XRD and Rietveld Refinement process. The saturated magnetization obtained from the VSM is found to decrease first by the irradiation and then increase drastically. This analysis is performed by the popular pulse field technique of hysteresis loop for nano ferrites and further analyzed by LAS. The frequency dependent characteristics such as dielectric constant, electric modulus, impedance analysis and ac conductivity are inspected for all samples with both types of irradiation process. The electrical modulus Cole-Cole plots insure the dominant property as electric stiffness for investigated ferrties. Extreme decrease has been found in the dielectric natures which also show good agreement in the higher ac conductivity nature at the higher frequencies. Electrical parametric dependent overlapping two semicircles which are not complete have been found in the plots of Cole-Cole for impedance data. The energy of activation for the process of diffusion decreases by the irradiation.

Revealing the Chemical and Structural Complexity of Electrochemical Ion Exchange in Layered Oxide Materials.

Soft chemistry techniques, such as ion exchange, hold great potential for the development of battery electrode materials that cannot be stabilized via conventional equilibrium synthesis methods. Nevertheless, the intricate mechanisms governing ion exchange remain elusive. Herein, we investigate the evolution of the long-range and local structure, as well as the ion (de)intercalation mechanism during electrochemical Li-to-Na ion exchange initiated from an O3-type lithium-layered oxide cathode. The in situ-formed mixed-cation electrolyte leads to competitive intercalation of Li and Na ions. While Li ion intercalation predominates at the beginning of initial discharge, Na ion cointercalation into a different layer results in ion redistribution and phase separation, with the emergence of a P3-Na phase alongside an O3-Li phase. Further, this study spatially resolves the heterogeneous nature of electrochemical ion exchange reactions within individual particles and provides insights into the correlations between local Ni redox processes and phase separation. Overall, electrochemical ion exchange leads to a mixed-phase cathode and alters its reaction kinetics. Those findings have important implications for the development of new metastable materials for renewable energy devices and ion separation applications.

A perturbative multi-mode model with finite parallel electric field for fast-ion-driven Alfvén eigenmodes

Abstract Alfvén eigenmodes are of great interest in any fusion device as they can be excited by fast ions in the plasma. If the modes grow to large amplitudes, they can cause transport and redistribution of the fast ions, thus limiting fusion performance. To save computational resources, the resonant kinetic interaction between the fast-particle species and the modes is often modelled by MHD-kinetic hybrid codes. Here, we present such a hybrid model which is applicable to three-dimensional magnetic fields, accounts for a finite parallel electric field and multiple MHD modes present at the same time. The model extends the one previously implemented in the CKA-EUTERPE code allowing for a better estimate of the damping due to the parallel electric field and nonlinear mode-mode interaction. The capabilities of our model are illustrated by applying the code to model nonlinear frequency chirping and fast-ion profile flattening.

Solution-Processed Polymer Memcapacitors with Stimulus-Controlled and Evolvable Synaptic Functionalities: From Short-Term Plasticity to Long-Term Plasticity to Metaplasticity.

In the vanguard of neuromorphic engineering, we develop a paradigm of biocompatible polymer memcapacitors using a seamless solution process, unleashing comprehensive synaptic capabilities depending on both the stimulation form and history. Like the human brain to learn and adapt, the memcapacitors exhibit analogue-type and evolvable capacitance shifts that mirror the complex flexibility of synaptic strengthening and weakening. With increasing frequency and intensity of the stimulation, the memcapacitors demonstrate an evolution from short-term plasticity (STP) to long-term plasticity (LTP), and even to metaplasticity (MP) at a higher level. A physical picture, featuring the stimulus-controlled spatiotemporal ion redistribution in the polymer, elaborates the origin of the memcapacitive prowess and resultant versatile synaptic plasticity. The distinctive MP behavior endows the memcapacitors with a dynamic learning rate (LR), which is utilized in an artificial neural network. The superiority of implementing a dynamic LR compared with conventional practices of using constant LR shines light on the potential of the memcapacitors to exploit organic neuromorphic computing hardware.

Nonlinear simulations of GAEs in NSTX-U

A set of nonlinear simulations has been performed in order to study the nonlinear evolution of unstable global Alfvén eigenmodes in the National Spherical Torus Experiment-Upgrade (NSTX-U). Results of the single toroidal mode number, n, simulations are compared with a full nonlinear simulation (all toroidal harmonics included). In single-n simulations, the conservation of two integrals of motion of a particle in a cyclotron resonance with a monochromatic wave is demonstrated, resulting in a one-dimensional evolution of the particle distribution in (E,μ,pϕ) phase-space. Nonlinear simulations (both single-n and full nonlinear) show a significant redistribution of the resonant fast ions, especially in the pitch parameter. Thus, the changes in the resonant particle's parallel and perpendicular energies can be several times larger than the total particle energy change, with only a small fraction transferring into the excitation of the mode itself. This implies that even a relatively small amplitude mode can significantly modify the beam distribution in the resonant region. For the NSTX-U case considered, the single-n simulation results are close to full nonlinear simulation only for the most unstable mode, in which case the saturation amplitudes and changes in the fast ion distribution are comparable. In contrast, peak amplitudes of subdominant modes in all-n simulations are smaller by a factor of 3–10 compared to single-n runs due to the flattening of the beam ion distribution by the fastest growing mode.

Emerging role of MXene in energy storage as electrolyte, binder, separator, and current collector: A review

Numerous energy storage parts can benefit from valuable and unique properties of MXenes. MXenes serve a variety of purposes in batteries and supercapacitors, including substrates for electrodeposition, steric hindrance, ion redistribution, bilayer and oxidation/reduction ion storage, ion transfer regulation, and more. They have been used to improve the performance and stability of separators, electrolytes and electrodes. Here, we discuss about various MXene preparation methods, its numerous physicochemical properties, and then present some recent studies in which MXene-based materials have been used as electrolytes, separators, current collectors, and binders in energy storage devices. Finally, we provide an outlook on the prospects and challenges associated with energy storage device components based on MXene and probable direction for future applications.

Applied Electric Field Effects on Diffusivity and Electrical Double-Layer Thickness.

This study utilizes molecular dynamics (MD) simulations and continuum frameworks to explore electroosmotic flow (EOF) in nanoconfined aqueous electrolytes, offering a promising alternative to conventional micro-/nanofluidic systems. Although osmotic behavior in these environments is deeply linked to local fluid properties and interfacial dynamics between the fluid and electrolyte solutions, achieving a complete molecular-level understanding has remained challenging. The findings establish a linear relationship between electric field strength and fluid velocity, uncovering two distinct transport regimes separated by a critical threshold, with a markedly intensified flow in the second regime. It is demonstrated that rising electric field strengths significantly enhance water diffusion coefficients, supported by a detailed analysis of fluid hydration structures, the potential of mean force (PMF), and local stress tensors. Due to the applied electric field strength, the motion of ions and water accelerates, leading to the redistribution of ions and intensification of electrostatic forces. This expands the thickness of the electric double layer (EDL) and amplifies fluid diffusivity, thereby enhancing nanoscale fluid activity. These insights enhance the molecular-level understanding of EOF and define the stability of flow regimes, providing valuable guidelines for advancing nanofluidic technologies, such as drug delivery systems and lab-on-a-chip devices.

Efficient mitigation of lithium dendrite by two-dimensional A-type molecular sieve membrane for lithium metal battery

Uneven lithium deposition poses a primary challenge for lithium-ion batteries, as it often triggers the growth of lithium dendrites, thereby significantly compromising battery performance and potentially giving rise to safety concerns. Therefore, the high level of safety must be guaranteed to achieve the large-scale application of battery energy storage systems. Here, we present a novel separator design achieved by incorporating a two-dimensional A-type molecular sieve coating onto the polypropylene separator surface, which functions as an effective lithium ion redistribution layer. The results demonstrated that even after undergoing 1000 cycles, the cell equipped with a two-dimensional A-type molecular sieve-Polypropylene (2D-A-PP) separator still maintains an impressive capacity retention rate of 70 %. In contrast, cells equipped with Polypropylene (PP) separators exhibit capacity retention rates below 50 % after only 500 cycles. Additionally, the incorporation of a two-dimensional molecular sieve enhances the mechanical properties of the PP separator, thereby bolstering battery safety. This study proposes a novel concept for the design of lithium-ion battery separator materials, offering a fresh perspective on the development of separators with exceptional thermal stability, enhanced porosity, superior electrolyte affinity, and effective inhibition of lithium dendrite formation.

Self‐Selective Crossbar Synapse Array with n‐ZnO/p‐NiOx/n‐ZnO Structure for Neuromorphic Computing

AbstractArtificial synapse devices are essential elements for highly energy‐efficient neuromorphic computing. They are implemented as crossbar array architecture, where highly selective synaptic weight updates for training and sneak leakage‐free inference operations are required. In this study, self‐selective bipolar artificial synapse device is proposed with n‐ZnO/p‐NiOx/n‐ZnO heterojunction, and its analog synapse operation with high selectivity is demonstrated in 32 × 32 crossbar array architecture without the aid of selector devices. The built‐in potential barrier at p‐NiOx/n‐ZnO junction and the Zener tunneling effect provided nonlinear current–voltage characteristics at both voltage polarities for self‐selecting function for synaptic potentiation and depression operations. Voltage‐driven redistribution of oxygen ions inside n–p–n oxide structure, evidenced by x‐ray photoelectron spectroscopy, modulated the distribution of oxygen vacancies in the layers and consequent conductance in an analog manner for the synaptic weight update operation. It demonstrates that the proposed n–p–n oxide device is a promising artificial synapse device implementing self‐selectivity and analog synaptic weight update in a crossbar array architecture for neuromorphic computing.

Fabrication of Isotope-Enriched Nanostructures Using Ultrafast Laser Pulses under Ambient Conditions for Biomolecular Sensing.

Recent advances in the use of stable isotopes necessitate novel synthesis techniques for isotope separation and enrichment that are scalable and offer high throughput. Stable-isotope-enriched nanostructures can offer unique advantages as nanomedicines, safe tracers, and labels and are critical for applications in various industrial processes, metabolic research, and medicine. So far, there exists no method to synthesize miniature isotope-enriched materials at the nanoscale. In this study, an ultrafast Laser-induced isotope enrichment at nanoscale (LIIEN) is put forward to synthesize isotope-enriched nanostructures, eliminating the need for large equipment and expenses, thereby demonstrating a lab-scale isotope enrichment process. A significant isotope enrichment for Carbon nanostructures is observed. The isotope enrichment can be attributed to the redistribution of isotope ions in the plasma plume explained by the plasma centrifuge model. The LIIEN synthesized structures exhibit excellent Surface-Enhanced Raman Scattering (SERS)signal enhancement and reproducibility, making them potential candidates for SERS-based biomolecule sensing. This technique is an efficient method to fabricate nanosized isotope-enriched structures of characteristic properties by carefully tuning laser parameters at ambient conditions.

Memristive Characteristics in an Asymmetrically Charged Nanochannel.

The emergent nanofluidic memristor provides a promising way of emulating neuromorphic functions in the brain. The conical-shaped nanopore showed promising features for a nanofluidic memristor, inspiring us to investigate the memory effects in asymmetrically charged nanochannels due to their high current rectification, which may result in good memory effects. Here, the memory effects of an asymmetrically charged nanofluidic channel were numerically simulated by Poisson-Nernst-Planck equations. Our results showed that the I-V curves represented a diode in low scanning frequency and then became a memristor and finally a resistor as frequency increased. We successfully replicated the learning behavior in our system with history-dependent ion redistribution in the nanochannel. Some critical factors were quantitatively analyzed for the memory effects including voltage amplitude, optimal frequency, and Dukhin number. Experimental characterizations were also carried out. Our findings are useful for the design of nanofluidic memristors by the principle of enrichment and depletion as well as the determination of the best memory settings.

Revealing the characteristics of oxygen evolution reaction performance of NiZn ferrites

Magnetic field-assisted method has been proved as an effective method to improve oxygen evolution reaction performance (OER) of water splitting, however, the essential reason for the improvement of OER performance still remains unclear. Herein, Ni1-xZnxFe2O4 ferrites were prepared by the combination of hydrothermal and calcination method, the magnetic properties, oxygen evolution reaction performance and the effect of applied magnetic field on OER performance were studied and discussed according to the magnetic properties and ion site situation. The magnetic field effect depended on the applied magnetic field strength and the magnetic magnetization density of catalysts, it was attributed to changes of electron state and redistribution of ions in the spinel structure. The overpotential decreased by approximately 50 mV and its double layer capacitance increased about 60 % at 125 mT applied magnetic field. The results provided a newness research view for the domain of electrochemistry.

A universal pre-charging method for enhancing transient speed in Organic Electrochemical Transistors

Organic electrochemical transistors (OECT) have shown great potential in diverse applications; however, in many OECTs, their slow transient response has thus far limited their practical use. One reason for the slow response is the complex interplay between lateral and vertical ion transport that has so far been poorly understood. In this work, we study the impact of lateral ion transport on OECT transient response, introduce a robust pre-charging method to manipulate the slow lateral ion transport. This approach leads to quicker ion redistribution and improved switching speeds. We show the general utility of pre-charging method in enhancing the switching speeds across various material systems, characterized by both low and high ion mobilities, and across different device architectures, achieving nearly symmetric speeds for both on-switching and off-switching. Moreover, we showcase the efficacy of the pre-charging method in enabling slow OECTs to capture rapid signals in real-world applications. Our findings present a groundbreaking strategy for enhancing the response times of OECT devices and deepening our understanding of the transient mechanisms in OECT device.