Cation Conductance Research Articles

Functional Assessment of Rat Sciatic Nerve Regeneration Using a Nerve Conduit Based on Ion Exchange Membrane.

The problem with modern nerve conduits is inability to transmit nerve impulses to the distal part of the damaged nerve. Cationic conductivity is a necessary characteristic of the nerve conduit ensuring effective regeneration of the peripheral nerves. We performed a functional assessment of the regeneration of rat sciatic nerve using a nerve conduit based on an ion-exchange membrane. A sciatic nerve defect was experimentally simulated in Wistar rats with further implantation of the LF-4SK membrane. On days 60 and 90 after surgery, the sciatic functional index and the ratio of the shin girth of the operated limb to the intact limb were calculated; on day 90, an electrophysiological assessment of nerve recovery was carried out. The results of the study showed that the conduit based on the LF-4SK membrane optimizes the functional recovery of the sciatic nerve defect.

Influence of Molecular Weight and End Groups on Ion Transport in Weakly and Strongly Coordinating Polymer Electrolytes

AbstractIn the development of polymer electrolytes, the understanding of the complex interplay of factors that affect ion transport is of importance. In this study, the strongly coordinating and flexible poly (ethylene oxide) (PEO) is compared to the weakly coordinating and stiff poly (trimethylene carbonate) (PTMC) as opposing model systems. The effect of molecular weight (Mn) and end group chemistry on the physical properties: glass transition temperature (Tg) and viscosity (η) and ion transport properties: transference number (T+), ion coordination strength and ionic conductivities were investigated. The cation transference number (T+) showed the opposite dependence on Mn for PEO and PTMC, decreasing at low Mn for PTMC and increasing for PEO. This was shown to be highly dependent on the ion coordination strength of the system regardless of whether the end group was OH or if the chains were end‐capped. Although the coordination is mainly of the cations in the systems, the differences in T+ were due to differences in anion rather than cation conductivity, with a similar Li+ conductivity across the polymer series when accounting for the differences in segmental mobility.

Твёрдые полимерные электролиты на основе нафиона для литий-ионных и натрий-ионных аккумуляторов

The use of solid polymer electrolytes is a novel and promising approach for enhancing the safety of lithium-ion and sodium-ion batteries. A number of publications on manufacturing electrolytes with lithium-ion and sodium-ion conductivity based on Nafion-like polymers have appeared in recent decade. The present mini-review analyses various methods of the synthesis of such electrolytes and their properties, as well as the information on laboratory lithium-ion and sodium-ion batteries using such electrolytes. The conclusion is made that the use of Nafion-based solid polymer electrolytes with Li+ and Na+ cation conductivity opens the way to creation of a new generation of lithium-ion and sodium-ion batteries. The principal advantage of Nafion-based solid polymer electrolytes over traditional PEO-based electrolytes is a fairly high cation transport number, which provides a sharp decrease in concentration polarization and, consequently, the increase in the energy efficiency of batteries.

Mechanisms of mechanotransduction and physiological roles of PIEZO channels.

Mechanical force is an essential physical element that contributes to the formation and function of life. The discovery of the evolutionarily conserved PIEZO family, including PIEZO1 and PIEZO2 in mammals, as bona fide mechanically activated cation channels has transformed our understanding of how mechanical forces are sensed and transduced into biological activities. In this Review, I discuss recent structure-function studies that have illustrated how PIEZO1 and PIEZO2 adopt their unique structural design and curvature-based gating dynamics, enabling their function as dedicated mechanotransduction channels with high mechanosensitivity and selective cation conductivity. I also discuss our current understanding of the physiological and pathophysiological roles mediated by PIEZO channels, including PIEZO1-dependent regulation of development and functional homeostasis and PIEZO2-dominated mechanosensation of touch, tactile pain, proprioception and interoception of mechanical states of internal organs. Despite the remarkable progress in PIEZO research, this Review also highlights outstanding questions in the field.

Cl--dependent amplification of excitatory synaptic potentials at distal dendrites revealed by voltage imaging.

The processing of synaptic signals in somatodendritic compartments determines neuronal computation. Although the amplification of excitatory signals by local voltage-dependent cation channels has been extensively studied, their spatiotemporal dynamics in elaborate dendritic branches remain obscure owing to technical limitations. Using fluorescent voltage imaging throughout dendritic arborizations in hippocampal pyramidal neurons, we demonstrate a unique chloride ion (Cl-)-dependent remote computation mechanism in the distal branches. Excitatory postsynaptic potentials triggered by local laser photolysis of caged glutamate spread along dendrites, with gradual amplification toward the distal end while attenuation toward the soma. Tour de force subcellular patch-clamp recordings from thin branches complemented by biophysical model simulations revealed that the asymmetric augmentation of excitation relies on tetrodotoxin-resistant sodium ion (Na+) channels and Cl- conductance accompanied by a more hyperpolarized dendritic resting potential. Together, this study reveals the cooperative voltage-dependent actions of cation and anion conductance for dendritic supralinear computation, which can locally decode the spatiotemporal context of synaptic inputs.

Resting human trabecular meshwork cells experience tonic cation influx.

The trabecular meshwork (TM) regulates intraocular pressure (IOP) by converting biochemical and biomechanical stimuli into intracellular signals. Recent electrophysiological studies demonstrated that this process is mediated by pressure sensing ion channels in the TM plasma membrane while the molecular and functional properties of channels that underpin ionic homeostasis in resting cells remain largely unknown. Here, we demonstrate that the TM resting potential is subserved by a powerful cationic conductance that disappears following Na+ removal and substitution with choline or NMDG+. Its insensitivity to TTX, verapamil, phenamil methanesulfonate and amiloride indicates it does not involve voltage-operated Na+, Ca2+ and epithelial Na+ (ENaC) channels or Na+/H+ exchange while a modest hyperpolarization induced by SEA-0440 indicates residual contribution from reversed Na+/Ca2+ exchange. Tonic cationic influx was inhibited by Gd3+ and Ruthenium Red but not GsMTx4, indicating involvement of TRP-like but not Piezo channels. Transcriptional analysis detected expression of most TRP genes, with the canonical transcriptome pool dominated by TRPC1 followed by the expression ofTRPV1, TRPC3 and TRPC5. TRPC3 antagonist Pyr3 and TRPC1,4,5 antagonist Pico1,4,5 did not affect the standing current, whereas the TRPC blocker SKF96365 promoted rather than suppressed, Na+ influx. TM cells thus maintain the resting membrane potential, control Na+ homeostasis, and balance K+ efflux through a novel constitutive monovalent cation leak current with properties not unlike those of TRP channels. Yet to be identified at the molecular level, this novel channel sets the homeostatic steady-state and controls the magnitude of pressure-induced transmembrane signals.

Evaluation of mechanisms involved in regulation of intrinsic excitability by extracellular calcium in CA1 pyramidal neurons of rat.

It is well recognized that changes in the extracellular concentration of calcium ions influence the excitability of neurons, yet what mechanism(s) mediate these effects is still a matter of debate. Using patch-clamp recordings from rat hippocampal CA1 pyramidal neurons, we examined the contribution of G-proteins and intracellular calcium-dependent signaling mechanisms to changes in intrinsic excitability evoked by altering the extracellular calcium concentration from physiological (1.2 mM) to a commonly used experimental (2 mM) level. We find that the inhibitory effect on intrinsic excitability of calcium ions is mainly expressed as an increased threshold for action potential firing (with no significant effect on resting membrane potential) that is not blocked by either the G-protein inhibitor GDPβS or the calcium chelator BAPTA. Our results therefore argue that in the concentration range studied, G-protein coupled calcium-sensing receptors, non-selective cation conductances, and intracellular calcium signaling pathways are not involved in mediating the effect of extracellular calcium ions on intrinsic excitability. Analysis of the derivative of the action potential, dV/dt versus membrane potential, indicates a current shift towards more depolarized membrane potentials at the higher calcium concentration. Our results are thus consistent with a mechanism in which extracellular calcium ions act directly on the voltage-gated sodium channels by neutralizing negative charges on the extracellular surface of these channels to modulate the threshold for action potential activation.

Covalent–Organic‐Framework Membrane with Aligned Dipole Moieties for Biomimetic Regulable Ion Transport

AbstractBiological ion channels are renowned for their exceptional ion transport selectivity and adaptability to environmental changes, posing a significant challenge for synthetic mimicry. Herein, an innovative covalent–organic‐framework membrane featuring aligned benzothiadiazole units within its oriented 1D nanochannels is reported. These densely arrayed dipolar benzothiadiazole units enhance selective ion adsorption and facilitate membrane charge regulation. Consequently, the membrane can dynamically adjust its permselectivity toward ions, transitioning seamlessly between cation‐selective, ambipolar, and anion‐selective states. This versatility affects both the type of ions transported and the transport efficiency, supporting reversible and controlled membrane operation, as illustrated by the capacity to regulate the magnitude and direction of osmotic power. When interacting with multivalent anions, highly negatively charged channels of the membrane exhibit outstanding cation permselectivity and conductivity. Specifically, upon exposure to PO43− ions, the membrane achieves a remarkable osmotic power of 155 W m−2 and an energy conversion efficiency of 46.1% under salinity gradients of 0.5 and 0.01 m NaCl. Notably, introducing multivalent cations can reverse the polarity of the membrane. This work underscores the potential of exploiting ion‐dipolar interactions for the development of adaptive, ion‐selective membranes with promising applications in electrochemical sensing, energy conversion, and more.

Highly Efficient, Flexible, and Self-Healable Moisture-Driven Energy Harvester Based on 2D Vanadium Pentoxide Nanosheets

The ubiquitous source of atmospheric moisture brought about a fascinating research avenue of extracting atmospheric water to generate sustainable electricity. Energy may be extracted from ambient moisture with obvious and substantial advantages. This point-of-use technology provides a decentralized alternative to meet the energy needs in isolated off-grid places. Unlike traditional energy generators which predominantly rely upon fossil fuel, moisture-induced energy generators can extract energy from moisture in a sustainable and eco-friendly way. Herein, we demonstrated a self-healable moist electric generator (MEG) based on vanadium pentoxide (V2O5) 2D nanosheet membranes. Lamellar membranes of V2O5 nanosheets have been shown to be excellent cation conductors and excellent materials for harvesting energy from ambient moisture. Ultra-thin 2D nanosheets of V2O5 was obtained by treatment of bulk V2O5 crystals with hydrogen peroxide. V2O5 nanosheet membrane was fabricated by vacuum-assisted filtration of 2D V2O5 nanosheets dispersion over a PTFE support membrane. The V2O5 membrane was easily peeled off from the support membrane on drying to obtain a flexible and freestanding V2O5 membrane. The V2O5 membrane consisting of percolated nanofluidic channels was sandwiched between a bottom solid copper foil and a perforated copper foil as the bottom electrode. The top electrode is perforated for exposure to atmospheric humidity. As the atmospheric water molecules come in contact with the V2O5 surface, an open-circuit voltage of 0.5 Volts and a short-circuit current of 0.3 microamperes is generated. The generated voltage and current is attributed to the preferential flow of cations through the V2O5 nanochannels. The exposed surface and edges of V2O5 nanosheets have a high negative surface charge which results in the splitting of water molecules into H3O+ and OH- ions. An electrical double layer (EDL) is established at the V2O5/water interface which selectively permits H3O+ ions through the channels. The mobile ions of the EDL transport through the nanofluidic channels creating a gradient between the two electrodes, resulting in a constant potential difference between the top and bottom electrodes which is harvested as electric current. The MEGs can be easily connected in parallel or series to enhance the current and voltage respectively. We demonstrate ten MEGs connected in series to power small electronic devices such as calculators and humidity meters. One of the key features of the V2O5 MEG is its ability to repair any physical damage to the active material owing to the water-assisted healing characteristics V2O5 membrane. Figure 1

Abstract Mo064: Na + leak channel NALCN plays an essential role in mineralocorticoid-induced hypertension through nonrenal mechanisms.

In human and animal hyperaldosteronism-related hypertension, the increased blood volume has been regarded as a primary contributor to hypertension generation. However, increases in arterial contractility (and thus peripheral resistance) are also frequently reported in various hypertension models, including the mineralocorticoid-induced hypertensions such as DOCA-salt hypertension. Moreover, non-renal mechanisms (i.e., direct regulation on the cardiovascular ion channels) of the mineralocorticoid-induced hypertension are reportedly important. Na + -leak channel (NALCN) was first cloned as Na + /Ca 2+ channel family in 1999. However, its role in providing background cation conductance and contributing to normal neuronal excitability has been uncovered relatively recently and little is known about the roles of NALCN in cardiovascular system and pathogenesis of hypertension. Here, we show that aldosterone directly upregulates NALCN expression in arterial smooth muscle independent of kidney and contribute to the increases in arterial contractility, thereby contributing to the development of hypertension. Remarkably, mere the transient knockdown of arterial NALCN greatly ameliorated the development of hypertension along with arterial hypercontractility. Moreover, it is very interesting that our findings suggest that NALCN is activated by oxidative stimuli and this activation can be prevented by -gliflozin series SGLT2 inhibitors. From these, we propose that NALCN is a very promising and potent target for the treatment of various hypertensions including mineralocorticoid-related one.

Mixed-Alkali Effect in Glasses of Different Classes in the Framework of a Microinhomogeneous-Glass-Structure Model

By example of the silicate glasses with the compositions (33.3 – x) Li2O · xNa2O · 66.7SiO2 and (33.3 – x) K2O · xNa2O · 66.7SiO2 with purely cationic conductance and chalcogenide glasses (Ag–Cu)0.33AsSe1.5 and (Ag–Cu)0.61AsSe1.5 with mixed ionic-electronic conductance, consideration has been given to the describing of the mixed-alkali effect in bimetallic glasses in the framework of a microinhomogeneous-glassstructure model using additive schemes involving concentration dependences of conductivity of monometallic glasses with the monovalent metal content equal to that in the mixed glass. A satisfactory agreement between experimental and calculated data is demonstrated. Herein, in the alkaline silicate glasses the nonlinear variation of the conductivity parameters is connected with the migration of two alkaline cations and sequential replacement of the conductance mainly involving an ion by that involving another ion. In the studied chalcogenide glasses, a similar varying of electrical parameters is connected with the replacement of the majority current carrier upon the equivalent substituting of copper for silver in the glass bulk: the mixed, predominantly ionic conductance is replaced by purely electronic one.

Ligand substitution as a strategy to tailor cationic conductivity in all-solid-state batteries

An increased electrification of society calls for a revolution of battery technologies to further improve energy densities, safety and reduce dependencies on critical raw materials. Here we present a new type of fast magnesium electrolytes for all solid-state batteries created as solid solutions of two other fast Mg2+ ionic conductors, Mg(BH4)2 ∙ NH3 and Mg(BH4)2 ∙ CH3NH2. However, the different ligands introduce stacking faults in the structures of the solid solutions, which are eliminated upon heating to T > 40 °C. The stacking faults appear to influence ionic conductivity, as the samples are less conductive after heating. Interestingly, the ionic conductivity does not correlate directly with the relative ligand content, as the highest conductivity is observed for the 1:1 molar composition (σ(Mg2+) = 7.3 ∙ 10−6 S cm−1 at 40 °C), which also has the lowest melting point of 60 °C. Thus, this work demonstrates a new approach to increase cationic conductivity using mixed ligand systems to alter conduction pathways and introduce microstructural strain.

Electrical conductivity of potassium polyferrite doped with doubly charged cations

To clarify the charge compensation mechanism and the way of alloying additives placement, the authors synthesised samples of potassium βʺ-polyferrites with a wide range of mole fraction of introduced doubly charged cations. For these samples, the authors measured the electronic conductivity, cationic conductivity, and performed X-ray diffraction (XRD) analysis. The authors identified the charge compensation mechanism in potassium β″-polyferrite when doped with divalent ions of calcium, strontium, magnesium, and zinc. The charge compensation mechanisms differ depending on the radius of the introduced doubly charged ion. The results of cationic conductivity measurements of potassium β″-polyferrites show the mobility reduction of large calcium and strontium cations of potassium ions. Such additives are quite promising for improving the mechanical strength and thermal stability of the catalyst granules. They also increase the chemical stability of the contact granules. Corrosion resistance of pellets is a critical parameter. It determines the period of effective functioning of the catalyst. The data on electronic conductivity allow one to conclude that the introduction of Mg2+, Zn2+ cations sharply reduces the electron exchange in the structure of potassium β″-polyferrite. This should inevitably cause deactivation of the catalyst, while Ca2+ and Sr2+ ions do not reduce the electron transfer rate. Moreover, using the proposed approach will intensify the research process.

Moving Down Group 1: Analytical Challenges and Current Trends for Solid Polymer Electrolytes in Post‐Li Battery Applications

AbstractThe solid polymer electrolyte (SPE) field has traditionally struggled with sufficiently high cation conduction at room temperature. The reason for this is that ion transport is usually coupled to polymer chain mobility and as such is strongly temperature dependent. The diversification of battery technologies from Li‐ion into Na‐ and K‐ion batteries has revived efforts in the 80s and 90s to develop a broad conceptional understanding and to find overarching trends of the ion transport properties of SPEs based on Group 1 elements, Li+, Na+, K+, Rb+ and Cs+ (i. e. beyond Li). This development brings its own set of challenges, starting from additional constraints to measure heavier cations. With a clearer aim towards tangible battery applications, particularly electrochemical stability and interphase formation, and together with a rising sensibility of sustainability aspects, other parameters have gained more relevance and opened new vectors of research. The associated scientific challenges and recent developments of Group 1 based SPEs shall be reviewed.

Exhaustive Study of Electrical Conductivity in the MNb2−x TixO6–0.5x (M = Mg, Ca, Zn; x = 0, 0.1, 0.2) Columbites

The CaNb2O6 and ZnNb2O6 columbites (Sp.gr. Pbcn) were studied as oxygen ion conductors both theoretically and experimentally. A theoretical approach included geometrical-topological analysis, bond valence site energy (BVSE) and density functional theory (DFT) calculations. The BVSE approach showed the possibility of pure oxygen ions diffusion with migration energies less than 0.45 eV in both compounds. However, DFT calculations indicated the possibility of diffusion of both anions and cations. The single-phases columbites were synthesized by the Pechini method for accurately determine charge carriers type and investigated by impedance spectroscopy, by the Tubandt method, which confirmed the absence of cationic conductivity, and measured the electrical conductivity as a function of oxygen partial pressures. The CaNb2O6 sample was characterized by the pure oxygen-ionic conductivity ∼2 × 10−6 S cm–1 at 800 °C (E a = 0.82 eV), while the ZnNb2O6 had a similar conductivity value due to mixed ionic-electronic contribution (E a = 0.83 eV). The electromotive force method also showed the predominance of the ionic type of conductivity in CaNb2O6, while ZnNb2O6 has a mixed conductivity with ion transport number of about 0.4. Additionally, we synthesized Ti-doped samples MNb2−x Ti x O6–0.5x (M = Mg, Ca; x = 0.1, 0.2) to study the doping effect on conducting properties.

Unlocking the concentration polarization for Solid-State lithium metal batteries

Ceramic-polymer composite electrolytes for solid-state batteries are promising candidates due to the combination of safe reliability and mechanical flexibility. However, the sluggish lithium-ion transport and the inadequate electrochemical stability with high-voltage cathode materials limit the practical applications. Herein, we report a garnet-polymer solid electrolyte with high ionic conductivity and Li-ion transference number, favorable elasticity and good interface stability. A galvanostatic charge-relaxation process is designed to identify the inhibition effect of high Li-ionic transference number on concentration polarization and reveal its proportion to total polarization. By additionally adding lithium difluoro(oxalato)borate as stabilizer, the electrochemical window of the garnet-polymer composite electrolyte can extend to 5.3 V. The high cation conductivity and excellent antioxidant ability of composite electrolyte contribute to long cycling performance of LiNi0.8Mn0.1Co0.1O2 cathode at threshold voltage of 4.4 V. Furthermore, the pouch cell with high mass loading cathode and limited lithium anode was demonstrated successfully. Our findings provide an effective strategy on fabricating solid-state lithium-metal batteries towards practical applications.

Влияние концентрации перхлората лития на числа переноса катиона лития в сульфолановых растворах

To increase the accuracy of determining the lithium cation transference numbers we proposed to measure them at different values of the polarizing voltage and extrapolate the calculated values to the zero value of the polarizing voltage. It was established that the lithium cation transference numbers increased linearly with the increasing concentration of LiClO4 solutions in sulfolane. It is assumed that the increase in the lithium cation transference numbers takes place due to the change in lithium perchlorate state in sulfolane solution and the mechanism of ion transfer. It was shown that the maximum cation conductivity was achieved at the concentration of lithium perchlorate sulfolane solution of about 2M.

High carrier mobility in organic cations intercalated multilayer MoS2

Two-dimensional semiconductors, such as MoS2, have demonstrated great potential applications in post-Moore electronic and optoelectronic devices, and organic cations intercalation has been widely utilized to modulate their physical properties. However, the correlation between the conductivity, carrier mobility, carrier density, and structure of organic cations intercalated MoS2 is still unclear. In this Letter, we systematically investigated the structural and electrical transport properties of pristine MoS2 and MoS2 intercalated with various organic cations such as tetradecyltrimethyl-ammonium, tetraheptyl-ammonium, and cetyltrimethyl-ammonium. Semimetal bismuth (Bi) was used as electrodes to make Ohmic contact with MoS2, and four-probe measurements were employed to obtain the intrinsic conductivity of MoS2. The intercalated organic cations greatly expand interlayer spacing and strongly dope MoS2 up to an electron concentration of 6.1 × 1013 cm−2 depending on the size and intercalation amount of organic cations. The severe electron doping constrains the out-of-plane A1g vibration mode and screens the Coulomb scattering, such that the intercalated MoS2 has enhanced Hall mobility of >50 cm2 V−1 s−1 at room temperature and even >1700 cm2 V−1 s−1 at 5 K. The intercalated MoS2 responds much faster than pristine MoS2 when functioning as a phototransistor. Our work provides insight for understanding the electrical transport properties of MoS2 and designing more efficient electronic and optoelectronic devices.

Large-Scale, Vertically Aligned 2D Subnanochannel Arrays by a Smectic Liquid Crystal Network for High-Performance Osmotic Energy Conversion.

The osmotic energy, an abundant renewable energy source, can be directly converted to electricity by nanofluidic devices with ion-selective membranes. 2D nanochannels constructed by nanosheets possess abundant lateral interfacial ion-exchange sites and exhibit great superiority in nanofluidic devices. However, the most accessible orientation of the 2D nanochannels is parallel to the membrane surface, undoubtedly resulting in the conductivity loss. Herein, first vertically aligned 2D subnanochannel arrays self-assembled by a smectic liquid crystal (LC) network that exhibit high-performance osmotic energy conversion are demonstrated. The 2D subnanochannel arrays are fabricated by in situ photopolymerization of monomers in the LC phase. The as-prepared membrane exhibits excellent water-resistance and mechanical strength. The 2D subnanochannels with excellent cation selectivity and conductivity show high-performance osmotic energy conversion. The power density reaches up to about 22.5W m-2 with NaCl solution under a 50-fold concentration gradient, which is among with ultrahigh power density. This membrane design concept provides promising applications in osmotic energy conversion.

The influence of defects on conduction processes in chalcogenide semiconductor compounds

Due to the strong dependence on the intrinsic defectiveness of structures, semiconductor compounds based on metal chalcogenides have a wide spread in kinetic properties and high growth temperatures of materials, as well as a tendency to self-compensation of defects. It has been shown that an increase in defectivity in the cation sublattice leads to a decrease in ionic conductivity in copper chalcogenides, and an increase in temperature leads to an increase in ionic conductivity due to a change in mobility. The low activation energy indicates a strong intrinsic disorder of the cation part of the lattice. In copper chalcogenides, the presence of hopping conductivity at small deviations from stoichiometry is explained by compensation and a high concentration of vacancies. Under such conditions, this activation energy is the activation energy for the movement of copper ions throughout the crystal and almost all metal ions contribute to the ionic electrical conductivity. In semiconductor compounds based on metal chalcogenides with deviations from stoichiometry, the activation energy of cationic conductivity does not change, since the defects that arise in this case do not introduce large changes in ionic conductivity with temperature. The increase in ionic conductivity with increasing temperature is due to a change in mobility, since the carrier concentration remains unchanged. The latter is determined only by the structural features of the phases. Deviation from stoichiometry in compounds makes it necessary to take into account the movement of the main charge carriers in the allowed zones, and the movement of carriers along vacancies. The properties of metal chalcogenides are largely determined by the characteristics of their preparation and depend on the relative ratio of metal and chalcogen atoms, as well as the presence of intrinsic defects and their influence on the mechanism of behavior of charge carriers and transfer phenomena.