Study Of Ion Transport Research Articles

A Three-Dimensional Comprehensive Numerical Model of Ion Transport during Electro-Refining Process for Scrap-Metal Recycling.

A transient three-dimensional comprehensive numerical model was established to study ion transport caused by diffusion, convection, and electro-migration in the electro-refining process for scrap-metal recycling. The Poisson–Nernst–Planck equations were used to define ion transport within the electrolyte, while the Naiver–Stokes equations and the energy equation were employed to describe fluid flow and heat transfer. In addition, the Butler-Volmer formulation was used to represent the kinetics of the electrochemical reaction. The comparison between the measured and simulated data indicates the reliability of the model. Under the action of diffusion and electro-migration, the positive copper ion moves from the anode to the cathode, while the negative sulfate ion migrates in the opposite direction. The distribution of the ion concentration, however, greatly changes if the fluid flow is taken into account. The ion concentration around the anode and the rate of the electrochemical reaction that occurs at the anode surface are reduced by the fluid flow. The proposed computational framework offers a valuable basis for future research and development in the field of scrap-metal recycling technology.

Ion Transport in pH-Regulated Double-Barreled Nanopores.

Single-molecule detection and characterization with nanopores is a powerful technique that does not require labeling. Multinanopore systems, especially double nanopores, have attracted wide attention and have been applied in many fields. However, theoretical studies of electrokinetic ion transport in nanopores mainly focus on single nanopores. In this paper, for the first time, a theoretical study of pH-regulated double-barreled nanopores is conducted using three-dimensional Poisson-Nernst-Planck equations and Navier-Stokes equations. Four ionic species and the surface chemistry on the walls of the nanopores are included. The results demonstrate that the properties of the bulk salt solution significantly affect nanopore conductivity and ion transport phenomena in nanopores. There are two ion-enriched zones and two ion-depleted zones in double-barreled nanopores. Due to the symmetry of the double-barreled nanopore structure and surface charge density, there is no ionic rectification effect in double-barreled nanopores. The ion selectivity is similar to that of conventional single pH-regulated nanopores.

Pore-scale study of ion transport and intercalation processes of capacitive deionization cells with intercalation electrodes based on lattice Boltzmann method

Recently, CDIs with intercalation electrodes have attracted extensive attention due to their high ion storage capacity. A lattice Boltzmann (LB) model is developed to investigate the desalination process of intercalation CDIs on the pore-scale level. Numerical treatments on the boundary conditions at pore/particle interfaces are proposed to describe the ion and charge transfer across the interfaces. After validation of the LB model, pore-scale simulation is performed to reveal desalination dynamics of intercalation CDI under the constant current condition, and effects of current density, porosity and flow configuration on the desalination performance are investigated. Simulation results show that spatial distributions of concentration and intercalation degree within the porous electrode exhibit highly nonuniform and nonlinear characteristics during the adsorption process. The average salt adsorption rate (ASAR) can be improved by increasing the current density but with the sacrifice of reduction in the salt adsorption capacity (SAC). The SAC increases with the decrease of electrode porosity mainly due to the increment of time in the adsorption cycle, while the ASAR maintains unchanged for different porosities. Compared with the conventional flow-by configuration, the configuration with double flow channels is desirable for alleviating the concentration polarization across the electrode and thus improving the SAC.

Effect of Lithium Iodide on transport phenomenon in Lithium Borophosphate glass Electrolyte

Ion transport study for the lithium iodide doped Lithium Borophosphate (LBP) glass electrolyte x(LiI):[(100−x).(60Li2O:8B2O3:32P2O5)] has been carried out over a range of composition (x=0 to 25 wt.%). The electrical conductivity has been measured by complex impedance spectroscopy from 303 K to 423 K temperature. The physical parameter and conductivity study indicate to obey the Arrhenius relationship and the frequency dependent conductivity is in consonance with Jonscher's universal power law. The Correlated Barrier Hopping (CBH) model for ion transport is observed to follow in the present glass system. Further investigation of the conductivity has also been carried out to calculate the hopping frequency (ωp), relaxation time (τ), power-law exponent (n) and decoupling index (Rτ). The enthalpy for migration and free energy have been estimated using the frequency-dependent power-law exponent (n) behaviour. Charge dynamics between local states due to the activated hopping process has been discussed according to Anderson- Drago and Elliot's model. To reinforce the Lithium ion transport study, several physical parameters such as density (ρ), molar volume (VO), oxygen packing density (OPD), cation concentration (NLi), the mean distance between cations (R′LiI) and the total number of energy states per unit volume at Fermi level N(Ef) have been calculated using various empirical formulae to discuss the present LBP ionic glass system.

Microscopic study of ion transport in the porous electrode of a desalination battery based on the lattice Boltzmann method

Cation Intercalation Desalination (CID).

A detailed study of ion transport through the SARS-CoV-2 E protein ion channel.

The envelope (E) protein encoded in the genome of an RNA virus is crucial for the replication, budding and pathophysiology of the virus. In the light of the ongoing pandemic, we explored similarities/differences between SARS-CoV-1 and SARS-CoV-2 E protein ion channels in terms of their selectivity. Further, we also examined the impact of variation of the bath concentration and introduction of potential and concentration gradients across the channel on the binding ratios of sodium and chloride ions for the SARS-CoV-2 E protein. Ion transport is described through the fourth-order Poisson-Nernst-Planck-Bikerman (4PNPBik) model which generalizes the traditional model by including ionic interactions between ions and their surrounding medium and non-ionic interactions between particles due to their finite size. Governing equations are solved numerically using the immersed boundary-lattice Boltzmann method (IB-LBM). The mathematical model has been validated by comparing analytical and experimental ion activity. The SARS-CoV-1 E protein ion channel is found to be more permeable to cationic ions, while the SARS-CoV-2 E protein has similar selectivity for both cationic and anionic species. For SARS-CoV-2, an increase in the bath concentration results in an increase in the binding ratio for sodium ions. Furthermore, the chloride binding ratio increases as the concentration gradient increases. A potential gradient has a minimal effect on the binding ratio. The SARS-CoV-2 E protein was found to support higher ionic currents than the SARS-CoV-1 E protein. Furthermore, the ionic current increased with increasing bath concentrations.

Introduction to ion transport and membrane interactions in vascular health and disease.

Cardiovascular disease is on the rise, partially due to the continued increase in metabolic syndrome. Advances in basic research on vascular ion transport have the potential to provide targets for therapeutic interventions. Vascular specificity, which includes different vascular beds having different characteristics and the macro- vs. microvasculature, is a vitally important variable in characterization of ion transport. At the cellular level, targeted fluorescent biosensors for Ca2+, super-resolution microscopy, and organelle patch clamp electrophysiology enable more detailed studies. The "MetS/diabetes milieu" includes increased and decreased insulin, and increased glucose, increased LDL/HDL cholesterol and triglycerides, and increased blood pressure. The duration and severity of MetS/diabetes components certainly affect the vascular phenotype and ion transport and membrane interactions. A combination of in vivo animal models and in vitro cell models to study ion transport in MetS/diabetes conditions is optimal. Gene editing and selective pharmacological tools should be used after or in conjunction with characterization of ion transport in vascular health and disease phenotypes. This is critical to determining the causal role of Ca2+ signaling in modulation of vascular phenotype. The ion transport and membrane interactions that are measured are typically only a snapshot in time in these dynamic processes occurring over the progression of health and disease. It is imperative that this concept be considered in the planning of long-term studies of vascular disease, ion transport experiments, and interpretation of the data. Future directions for our contributors' research will advance the field.

Regulation of ionic current through a surround-gated nanopore via field effect control.

Ability to control ionic current flowing through a nanopore has been demonstrated using the electric field effect on an electrical gate surrounding the nanopore. The gate electrode was introduced onto a single nanopore by depositing an Au layer on a silicon nitride diaphragm prior to pore milling using a focused ion beam technique. A hafnium oxide layer was subsequently deposited onto the nanopore structure as an insulating layer to protect the gate electrode. The device operation was investigated in KCl electrolyte and the ionic current regulating ability was examined under the influence of the gate voltage and the nanopore size. It was found that the device shows significant ionic current response with respect to the applied gate voltage. The resulting electric field dependent behavior of the fabricated nanopore suggests that the ionic current is influenced by positive surface charge inside the nanopore. The gate influence was more pronounced in the smaller nanopore and with higher source-drain voltage. The gate and pore size dependence behavior allows the potential to regulate ionic current as a nanoscale valve in nanochannel applications.

Proton dynamics in water confined at the interface of the graphene-MXene heterostructure.

Heterostructures of 2D materials offer a fertile ground to study ion transport and charge storage. Here, we use ab initio molecular dynamics to examine the proton-transfer/diffusion and redox behavior in a water layer confined in the graphene-Ti3C2O2 heterostructure. We find that in comparison with the similar interface of water confined between Ti3C2O2 layers, the proton redox rate in the dissimilar interface of graphene-Ti3C2O2 is much higher, owing to the very different interfacial structure as well as the interfacial electric field induced by an electron transfer in the latter. Water molecules in the dissimilar interface of the graphene-Ti3C2O2 heterostructure form a denser hydrogen-bond network with a preferred orientation of water molecules, leading to an increase in proton mobility with proton concentration in the graphene-Ti3C2O2 interface. As the proton concentration further increases, proton mobility decreases due to increasingly more frequent surface redox events that slow down proton mobility due to binding with surface O atoms. Our work provides important insights into how the dissimilar interface and their associated interfacial structure and properties impact proton transfer and redox in the confined space.

Properties of electrode-supported lipid cubic mesophase films with embedded gramicidin A: structure and ion-transport studies

The lipid cubic phase (LCP) is a nanomaterial composed of water channels surrounded by lipid bilayers. LCPs are stable at room temperature and are biocompatible. These features make the lipid cubic phases similar to biological membranes, and hence, are favorable for embedding membrane proteins. We show that the monoolein cubic phase deposited on the electrode forms a 3D lipid bilayer film convenient for electrochemical investigations of membrane proteins. In this research, we studied the effect of embedding an ionophoric peptide, gramicidin A (gA), on the structure and properties of the LCP film. The phase identity and structural parameters of the gramicidin-doped phase were characterized by small-angle X-ray scattering (SAXS). The potassium ion transport through the film were studied by electroanalytical methods: alternating current voltammetry (ACV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). Increased values for the current of the gramicidin-doped cubic phase compared to the empty cubic phase and changes of the EIS parameters confirmed that the peptide remained in the film in its active dimeric form. Our results show that the LCP can be considered a suitable 3D biomimetic film for the investigation of ion channels and other transporting membrane proteins, and for their application in electrochemical sensors.

Correction to: Characterization and ion transport studies through impedance spectroscopy on (1-x)Pb(NO3)2:xAl2O3 composite solid electrolytes

Correction to: Characterization and ion transport studies through impedance spectroscopy on (1-x)Pb(NO3)2:xAl2O3 composite solid electrolytes

Operando Measurements of Electrolyte Li-ion Concentration during fast charging with FTIR/ATR

The ability to charge a Li-ion battery at high charging rates is critical for electric vehicle adoption; however, further study of ion transport is required to develop electrolytes suitable for fast charge. Fourier transform infrared spectroscopy (FTIR) used with attenuated total reflection (ATR) enables operando measurements of liquid electrolytes. This research focused on solvation shifting of solvent infrared absorption bands in the presence of lithium ions. Lithium-shifted infrared absorption bands and non-shifted bands of ethyl methyl carbonate (EMC) and ethylene carbonate (EC) were compared to infer ion concentration changes during cycling. Lithium concentrations were calibrated using EC/EMC/LiPF6 electrolytes with known lithium concentrations. A Li-ion half-cell with a graphite anode and EC/EMC/LiPF6 electrolyte was observed with FTIR/ATR. The results showed that the magnitude of lithium concentration changes increased with increasing C-rate. During a galvanostatic intermittent titration technique (GITT) test, changes in lithium concentration could be observed. During intercalation, a lithium depletion occurred when a negative current was applied, and a lithium surplus occurred during deintercalation when a positive current was applied. The capability of observing lithium concentration has significant implications for the utility of operando studies and the potential to link lithium movement to battery performance.

Ion Transport Study in Corn Starch-NaHSO3 Based Polymer Electrolytes

In this work, different amounts of sodium bisulfite, NaHSO3 (5wt.% to 40wt.%), were dissolved in a corn starch polymer host to synthesize solid polymer electrolyte (SPE) using a solution casting technique. Then, the films prepared were characterised using non-destructive electrical impedance spectroscopy to determine SPE films' conductivity and electrical transport properties. The highest conductivity of the sample at ambient temperature was recorded at 15wt. % of NaHSO3 with a value of 2.22 × 10-4 Scm-1. Moreover, the ion transport parameters at room temperature are found to be 2.41 × 10-7 cm2s-1, 9.39 × 10-6 cm2V-1s-1, 1.70 × 1019 cm-3 for D, µ and n, respectively. The conductivity of the samples was found dependent on diffusion coefficient, D and mobility, µ of ions.

Molecular Dynamics Study of Ion Transport in Polymer Electrolytes of All-Solid-State Li-Ion Batteries.

Atomistic analysis of the ion transport in polymer electrolytes for all-solid-state Li-ion batteries was performed using molecular dynamics simulations to investigate the relationship between Li-ion transport and polymer morphology. Polyethylene oxide (PEO) and poly(diethylene oxide-alt-oxymethylene), P(2EO-MO), were used as the electrolyte materials, and the effects of salt concentrations and polymer types on the ion transport properties were explored. The size and number of LiTFSI clusters were found to increase with increasing salt concentrations, leading to a decrease in ion diffusivity at high salt concentrations. The Li-ion transport mechanisms were further analyzed by calculating the inter/intra-hopping rate and distance at various ion concentrations in PEO and P(2EO-MO) polymers. While the balance between the rate and distance of inter-hopping was comparable for both PEO and P(2EO-MO), the intra-hopping rate and distance were found to be higher in PEO than in P(2EO-MO), leading to a higher diffusivity in PEO. The results of this study provide insights into the correlation between the nanoscopic structures of ion solvation and the dynamics of Li-ion transport in polymer electrolytes.

Exploring the versatility of the perfused crustacean gill as a model for transbranchial transport processes.

The study of transbranchial ion and gas transport of water-breathing animals has long been a useful means of modeling transport processes of higher vertebrate organs through comparative physiology. The molecular era of biological research has brought forward valuable information detailing shifts in gene expression related to environmental stress and the sub-cellular localization of transporters; however, purely molecular studies can cause hypothetical transport mechanisms and hypotheses to be accepted without any direct physiological proof. Isolated perfused gill experiments are useful for testing most of these hypotheses and can sometimes be used outright to develop a well-supported working model for transport processes relating to an animal's osmoregulation, acid-base balance, nitrogen excretion, and respiratory gas exchange as well as their sensitivity to pollutants and environmental stress. The technique allows full control of internal hemolymph-like saline as well as the ambient environmental fluid compositions and can measure the electrophysiological properties of the gill as well as the transport rates of ions and gases as they traverse the gill epithelium. Additives such as pharmaceuticals or peptides as well as the exclusion of ions from the media are commonly used to identify the importance of specific transporters to transport mechanisms. The technique can also be used to identify the penetrance, retention, and localization of pollutants within the gill epithelium or to explore the uptake and metabolism of nutrients directly from the ambient environment. While this technique can be applied to virtually any isolatable organ, the anatomy and rigidity of the decapod crustacean gill make it an ideal candidate for most experimental designs.

Focused ion beam milling based formation of nanochannels in silicon-glass microfluidic chips for the study of ion transport

Focused ion beam milling based formation of nanochannels in silicon-glass microfluidic chips for the study of ion transport

Ion-transport behavior in tetraethylene glycol dimethyl ether incorporated sodium ion conducting polymer gel electrolyte membranes intended for sodium battery application

In this paper, ion-transport behavior in poly(methyl methacrylate) based sodium-ion conducting polymer gel electrolyte membranes containing sodium triflate salt dissolved in tetraethylene glycol dimethyl ether (TEGDME) molecular liquid has been investigated by electrochemical impedance spectroscopy and other electrochemical ion-transport studies. The optimized polymer gel electrolyte membrane with 40 wt% TEGDME concentration offers a RT ionic conductivity of 3.6 × 10−3 S cm−1. The ion-transport behavior has been probed in wide range of frequency with the help of conductivity, dielectric and modulus studies. The structural studies reveal that the optimized electrolyte offers a porous structure with very low average roughness height of ~10 µm. The optimized flexible electrolyte membrane with an electrochemical stability window of ~4.4 V and sodium ion transport number close to 0.37 remains stable in the gel phase up to 150 °C. A proto-type RT Na-S battery utilizing the optimized electrolyte membrane display a stable open circuit potential of 2.24 V and delivers first discharge capacity as ~677 mA h g−1.

Dielectric relaxations and ion transport study of NaCMC:NaNO3 solid polymer electrolyte films

Na+ ion-conducting solid polymer electrolyte (SPE) of sodium salt of carboxymethyl cellulose (NaCMC) doped with sodium nitrate (NaNO3) was developed by solution casting method. FTIR technique confirmed the formation of hydrogen bonding between {NO}_3^{-} anion and functional groups of NaCMC. XRD study revealed the low degree of crystallinity that reduced upon doping. Impedance spectroscopy was adapted in order to analyze the conductivity and dielectric relaxation phenomena of the polymer-salt complex. FTIR deconvolution technique was employed to understand the factor that influences the ionic conductivity in SPE; concentration of mobile ions and ionic mobility both play a vital role. Ion transference number has been found out to be > 0.97 for all samples indicating that the conducting species are primarily ions. The highest ionic conductivity of ̴ 3 × 10−3 Scm−1 with the mechanical strength of 30.12 MPa was achieved for a host containing 30 wt.% NaNO3 at ambient temperature.

A Perspective on the Design of Ion-Containing Polymers for Polymer Electrolyte Applications.

Ion-containing polymers have numerous potential applications as energy storage and conversion devices, water purification membranes, and gas separation membranes, to name a few. Given the low dielectric constant of the media, ions and charges on polymers in a molten state interact strongly producing large effects on chain statistics, thermodynamics, and diffusion properties. Here, we discuss recent research accomplishments on the effects of ionic correlation and dielectric heterogeneity on the phase behavior of ion-containing polymers. Progress made in studying ion transport properties in these material systems is also highlighted. Charged block copolymers (BCPs), among all kinds of ion-containing polymers, have a particular advantage owing to their robust mechanical support and ion conducting paths provided by the segregation of the neutral and charged blocks. Coulombic interactions among the charges play a critical role in determining the phase segregation in charged BCPs and the domain size of charge-rich regions. We show that strongly charged BCPs display ordered phases as a result of electrostatic interactions alone. In addition, bulky charge-containing side groups attached to the charged block lead to the formation of morphologies that provide continuous channels and better dissociation for ion conduction purposes. Finally, a few avenues for designing ion-containing polymers for energy applications are discussed.

Designing Biomimic Two-Dimensional Ionic Transport Channels for Efficient Ion Sieving

Ion transport is crucial for biological systems and membrane-based technologies from both fundamental and practical aspects. Unlike biological ion channels, realizing efficient ion sieving by using membranes with artificial ion channels remains an extremely challenging task. Inspired by biological ion channels with proper steric containment of target ions within affinitive binding sites along the selective filter, herein we design a system of biomimic two-dimensional (2D) ionic transport channels based on a graphene oxide (GO) membrane, where the ionic imidazole group tunes the appropriate physical confinement of 2D ionic transport channels to mimic the confined cavity structures of the biological selectivity filter, and the ionic sulfonic group creates a favorable chemical environment of 2D ionic transport channels to mimic the affinitive binding sites of the biological selectivity filter. As a result, the as-fabricated ionic GO membrane demonstrates an exceptional K+ transport rate of ∼1.36 mol m-2 h-1 and competitive K+/Mg2+ selectivity of ∼9.11, outperforming state-of-the-art counterparts. Moreover, the semiquantitative studies of ion transport through 2D ionic transport channels suggest that efficient ion sieving with the ionic GO membrane is achieved by the high diffusion and partition coefficients of hydrated monovalent ions, as well as the large energy barrier and limited potential gradient of hydrated divalent ions encountered.