Ion Transport Processes Research Articles

The impact of interplanetary magnetic field intensity on the Martian ionosphere

The interplanetary magnetic field (IMF) is one of the important external drivers that controls the Martian-induced magnetosphere and ionosphere. Previous studies have shown that the ion escape process is highly influenced by both the direction and intensity of the IMF. The enhanced IMF may decrease the ion escape rate by inducing a stronger magnetosphere that protects the Martian ionosphere, but the mechanisms have not been investigated thoroughly. Further studies are needed to reveal the response of ionospheric heavy ions to IMF variation as well as the underlying physical mechanism. This study aims to investigate the influence the IMF strength has on the Martian ionosphere. We adopted a multifluid magnetohydrodynamic (MHD) model in this study, which can self-consistently simulate the interaction between solar wind and Mars. By comparing different cases, we analyzed the ionospheric structure on the dayside and near nightside as well as the ion transport process. We aim to obtain a deeper understanding of how the IMF intensity variation impacts the Martian ionosphere and the escape of planetary ions. A three-dimensional multifluid MHD model was used to simulate the interaction between the upstream solar wind and Mars. Four major species in the Martian ionosphere, H^+, O_ O^+, and CO_ are considered in the model, with the chemical reactions and particle collisions included to calculate ion distribution and ion motions. We analyzed three cases where the IMF strength was set to nT ， nT and nT The enhancement of the IMF produces a stronger electromagnetic field in the Martian plasma environment. Both the electric field and magnetic field intensity increase, which provides a shielding effect to the Martian ionosphere, hindering the intrusion of solar wind particles. Thus, less planetary ions are produced by the chemical reactions between the solar wind and the Martian neutral particles, leading to shrinkage of the ionospheric upper boundary. As the IMF strength increases, both the day-to-night plasma transport and the ion outflow decreases. Thus, a more depleted nightside ionosphere is formed, and the tailward ion escape may be weakened, decreasing the global ion escape rate. Moreover, the strong crustal fields in the southern hemisphere enhance the electromagnetic field on the southern dayside, which withstand the penetration of solar wind plasma more effectively, resulting in asymmetry structures in the ionosphere.

Water-mediated ion transport in an anion exchange membrane

Water is a critical component in polyelectrolyte anion exchange membranes (AEMs). It plays a central role in ion transport in electrochemical systems. Gaining a better understanding of molecular transport and conductivity in AEMs has been challenged by the lack of a general methodology capable of capturing and connecting water dynamics, water structure, and ionic transport over time and length scales ranging from those associated with individual bond vibrations and molecular reorientations to those pertaining to macroscopic AEM performance. In this work, we use two-dimensional infrared spectroscopy and semiclassical simulations to examine how water molecules are arranged into successive solvation shells, and we explain how that structure influences the dynamics of bromide ion transport processes in polynorbornene-based materials. We find that the transition to the faster transport mechanism occurs when the reorientation of water molecules in the second solvation shell is fast, allowing a robust hydrogen bond network to form. Our findings provide molecular-level insights into AEMs with inherent transport of halide ions, and help pave the way towards a comprehensive understanding of hydroxide ion transport in AEMs.

Reactivity of Wet scCO2 toward Reservoir and Caprock Formations under Elevated Pressure and Temperature Conditions: Implications for CCS and CO2-Based Geothermal Energy Extraction.

Carbon capture and storage (CCS) and CO2-based geothermal energy are promising technologies for reducing CO2 emissions and mitigating climate change. Safe implementation of these technologies requires an understanding of how CO2 interacts with fluids and rocks at depth, particularly under elevated pressure and temperature. While CO2-bearing aqueous solutions in geological reservoirs have been extensively studied, the chemical behavior of water-bearing supercritical CO2 remains largely overlooked by academics and practitioners alike. We address this knowledge gap by conducting core-scale laboratory experiments, focusing on the chemical reactivity of water-bearing supercritical CO2 (wet scCO2) with reservoir and caprock lithologies and simulating deep reservoir conditions (35 MPa, 150 °C). Employing a suite of high-resolution analytical techniques, we characterize the evolution of morphological and compositional properties, shedding light on the ion transport and mineral dissolution processes, caused by both the aqueous and nonaqueous phases. Our results show that fluid-mineral interactions involving wet scCO2 are significantly less severe than those caused by equivalent CO2-bearing aqueous solutions. Nonetheless, our experiments reveal that wet scCO2 can induce mineral dissolution reactions upon contact with dolomite. This dissolution appears limited, incongruent, and self-sealing, characterized by preferential leaching of calcium over magnesium ions, leading to supersaturation of the scCO2 phase and reprecipitation of secondary carbonates. The markedly differing quantities of Ca2+ and Mg2+ ions transported by wet scCO2 streams provide clear evidence of the nonstoichiometric dissolution of dolomite. More importantly, this finding represents the first reported observation of ion transport processes driven by water continuously dissolved in the scCO2 phase, which challenges prevailing views on the chemical reactivity of this fluid and highlights the need for further investigation. A comprehensive understanding of the chemical behavior of CO2-rich supercritical fluids is critical for ensuring the feasibility and security of deep geological CO2 storage and CO2-based geothermal energy.

The Structural, Electrical and Dielectric Studies of CMC Based Biopolymer Gel Electrolytes for Ecofriendly Device Applications

ABSTRACTThe solution casting procedure has been effectively used to synthesize biopolymer gel electrolytes (BGEs) using carboxymethyl cellulose (CMC) and ammonium thiocyanate (NH4SCN). The XRD patterns of the bio‐based green emulsions (BGEs) have provided evidence of the non‐crystalline structure of the films. Optical micrographs of BGEs have revealed the formation of homogeneous gel electrolyte films. Complex impedance spectroscopy has been used to investigate the ion transport mechanism and dielectric relaxation dynamics of biopolymer gel electrolyte films over a wide range of temperatures. The conductivity of the gel electrolyte samples has been shown to rise with the amount of salt present. The optimum ionic conductivity, determined at room temperature, is σ = 3.97 × 10−3 Scm−1, and it is achieved in the gel electrolyte sample containing 35 wt% NH4SCN. The variation in ionic conductivity with temperature has shown a blend of Arrhenius and Vogel‐Tamman‐Fulcher (VTF) characteristics. An analysis has been conducted on the impedance data to investigate the ion transport process using the formalisms of ac conductivity, permittivity, and electric modulus. The dielectric impedance of the BGEs films has been used to determine the charge carrier density and mobility. The electrolyte with the best conductivity has shown a broad range of electrochemical stability, spanning from −1.49 to +1.27 V. The I‐t investigations has shown a high transference number (tion ~ 0.99), indicating that ions are the primary contributors to conductivity. The cyclic voltammetry tests have shown excellent reusability, indicating its potential use in devices, such as supercapacitors and rechargeable batteries.

Sublethal effects of acidified water on sensorimotor responses and the transcriptome of zebrafish embryos.

Acidification of freshwater due to human activities is a widespread environmental problem. Its effects on the sensorimotor responses of fish, particularly during embryonic stages, may affect population fitness. To address this, zebrafish embryos were exposed to water at pH 7, 5 and 4.5 (adjusted with HCl) for 120 h. Acidic water did not increase mortality or cause obvious morphological abnormalities but reduced the size of the inner ear organs (otic vesicle and otolith) and the eye lens. It also suppressed ion uptake (Na+, Ca2+, K+) and induced embryonic acidosis. Behavioral tests at 4 or 5 days post fertilization revealed significant sensorimotor impairments: reduced touch-evoked escape responses (TEER), decreased acoustic startle responses (ASR) and decreased cadaverine avoidance responses (CAR). There were no effects on speed, acceleration and optomotor responses (OMR). Transcriptomic analyses identified 114 differentially expressed genes (DEGs) associated with ion transport, sensorimotor functions and other physiological processes. Overall, the jeopardizing effect of freshwater acidification threatens survival, highlighting the ecological risks and its potential impacts on fish populations.

(Invited) Mechanical Suppression of Electron Transfer in Subnanometer Confinement between MXene Layers

Ion adsorption and electron transfer are the primary charge storage mechanisms in porous electrodes. Desolvation/solvation of ions in subnanometer confinement may alter the balance between those two processes. For 2D materials like MXenes, there is a continuous change in interlayer spacing as ions are transported and stored between the layers. However, little is known about the effect of the mechanical constraint (pressure) on electrochemistry in confinement. In this work, the ion transportation process in between mechanically constrained MXene layers is monitored by combining in-situ UV-vis spectroscopy, in-situ optical spectroscopy, and in-situ XRD characterization. Compared with spray-coated Ti3C2Tx films, physically constrained Ti3C2Tx film with a constant interlayer spacing exhibited exceptional capabilities in suppressing redox reactions. Notably, this property of faradaic suppression under mechanical strain led to the application of MXene-based electrochemical cells as high-pressure electrochemical sensors.

(Invited) Enhancement of Li-Ion Intercalation Kinetics in High-Concentration Electrolytes

Highly concentrated electrolyte (HCE) solutions containing over 3 mol dm–3 of Li salts have attracted attention recently owing to their unique physicochemical and electrochemical properties such as high thermal and electrochemical stability, unusual Li+ ion transport processes, and good compatibility with next-generation batteries containing Li anodes. Certain HCEs enhance the charge-transfer reaction rate at the electrode/electrolyte interface in Li-ion batteries. The solvation structure of Li+ in HCEs significantly affects the electrochemical interfacial reaction kinetics. In the organic electrolytes of lithium-ion batteries, the desolvation process of Li+ ion at the electrode/electrolyte interface is the rate-limiting process of the charge transfer reaction.1 Our group has found that the rate of charge transfer reaction of Li+ intercalation electrode is affected not only by Li+ solvation structure but also by the activity of Li+ (aLi+)and viscosity in the electrolyte.2 In this study, the charge transfer resistance (Rct) of the LiMn2O4 (LMO)/electrolyte interface in the electrolyte with various Li salt concentrations was evaluated to determine the effect of Li+ activity and viscosity on the charge transfer kinetics. LMO thin-film electrodes were prepared using the polyvinylpyrrolidone (PVP) sol-gel method. The electrochemical measurements of the LMO thin-film electrode were performed using a three-electrode cell. Li metal was employed as both the counter and reference electrodes and a LMO thin film as the working electrode. The mixtures composed of LiN(SO2CF3)2 (LiTFSA) and monoglyme (G1) were used as model electrolytes. Electrochemical impedance spectroscopy (EIS) was conducted at 30 oC and 3.9 VLi to determine Rct. In the range of concentration less than 1.8 mol/L ([LiTFSA]/[G1] =1:4 in molar ratio), Rct decreases with increasing LiTFSA concentration, while it increases at higher than 1.8 mol L-1. The minimum Rct at 1.8 mol L-1 can be attributed to the combined effects of electrolyte viscosity and Li+ activity in the electrolyte. Further results including the reaction kinetics in other electrolytes also will be presented. Acknowledgements: This study was partially supported by the JSPS KAKENHI (Grant No. JP22H00340 and JP 23K17370).

Effects of Electrolyte Salts on Ionic Transport in Solid Polymer Electrolytes Investigated by Operando Raman Spectroscopy

Introduction To achieve carbon-neutral society, battery technologies have been attracting attention in recent years owing to its potential for storing renewable energy and serving as a load leveling power sources. In particular, all-solid-state batteries (ASSBs) utilizing non-volatile and flame-resistant solid electrolytes are actively investigated worldwide for practical implementation, as they are expected to enhance safety. Among solid electrolytes, solid polymer electrolytes (SPEs), which exhibit high flexibility and formability, are expected for their application in electrochemical devices such as ASSBs. In SPEs, cations are solvated by the host polymer and occurs ionic conducte through cooperative transport associated with segmental motion. The ionic transport properties of SPE, affected by molecular structures of electrolyte salt, and are further influenced by processes solvation/desolvation of cation and decomposition reactions under electrochemical conditions, is considered different from static states. Therefore, we focused on applying [Li | SPE | Li] symmetric cells and evaluated the ionic transport processes within SPE under reaction conditions using concentration changes through operando Raman spectroscopy measurements. In this study, we applied the measurement approach for use on SPEs incorporating LiN(SO2F)2 (LiFSA), LiN(SO2CF3)2 (LiTFSA), and LiN(SO2C2F5)2 (LiBETI) as Li salts to investigate the impact of anion structure/molecular weight on ionic transport mechanisms under actual reaction conditions. Experiments Li-based solid polymer electrolytes were prepared by mixing cross-linked polyether-based macromonomer P(EO/PO) (EO: PO = 8:2), Li salts (LiFSA, LiTFSA, LiBETI), and photopolymerization initiator DMPA in acetonitrile under an Ar atmosphere within a glovebox. The resulting solution was vacuum-dried and filled between glass plates using a spacer (thickness: 0.5 mm). Each SPE film was then fabricated by UV irradiation. To investigate the solvation structure and salt dissociation characteristics of SPE (salt concentration: [Li]/[O] = 0.04-0.16) under static conditions, Raman spectroscopy measurements were performed (NRS-4500: Jasco). A 9 mm × 9 mm rectangular-shaped [Li | SPE([Li]/[O]=0.04, 0.16) | Li] symmetric cell was prepared for in situ monitoring of concentration variations into the SPE during electrochemical reactions. The symmetric cell was introduced into a sealed cell with a quartz glass having monitoring window and connected to a potentiostat (HZ-7000, Hokuto Denko). In o perando Raman spectroscopy, Raman spectra were obtained from the vicinity of the working electrode (W.E.) and the counter electrode (C.E.) within the SPE during voltage application. The W.E. and C.E. regions were measured at points approximately 10-30 µm from the electrode/electrolyte interface. Results & Discussion Raman spectrum of the P(EO/PO)-LiTFSA(1) and LiBETI(2) system exhibited the peak at approximately 740 cm-1 derived from SNS vibration of TFSA and BETI anion. This peak, which increases with salt concentration, can be utilized as an indicator to evaluate concentration changes within the SPE induced by electrode reactions. To evaluate the ionic transport properties, operand o Raman spectroscopy measurements were performed using [Li | SPE([Li]/[O]=0.04, 0.16)|Li] symmetry cells. The peak area change (A/A 0) from the initial state was calculated by using the obtained Raman spectra. Fig. 1 and 2 exhibited the relationship between A/A 0 and applied voltage time calculated from measured points near W.E. and C.E. in symmetrical cells using the LiTFSA and LiBETI systems. In both Fig. 1 and 2, the peak area changes (A/A 0) were observed that concentrations near W.E. and C.E. increased or decreased with voltage application. In particular, the peak area changes (A/A 0) of the LiTFSA system exhibited a rapid increase in W.E. and decrease in C.E. within the initial 1 h of measurement, followed by no significant changes over 5 h (Fig. 1). This result suggests that the SPE has reached a steady state within at the end of the experiment. And in Fig. 1, the area changes (A/A 0) of [Li]/[O]=0.04 was significantly higher than that of [Li]/[O]=0.16. This results suggests that the faster ionic transport characteristics of [Li]/[O]=0.04 compared to [Li]/[O]=0.16 can be attributed to the lower concentration of the former. No significant changes were observed both [Li]/[O]=0.04 and 0.16 owing to changes in A/A 0, similar to LiTFSA system (Fig. 2). The lower ionic transport properties of LiBETI can be attributed to the larger molecular weight of BETI anion. These results indicated that the ionic transport mechanisms under reaction conditions differ depending on the anion structure (molecular weight).(1) I. Rey, et al, J. Electrochem. Soc., 145, 3034 (1998).(2) C. Capiglia, et al., J. Electrochem. Soc., 150, A525 (2003). Figure 1

Detangling Ion Transport and Lithium Dendritic Growth Using Stimulated Raman Scattering Microscopy

Ion transport is one of the fundamental processes in batteries, directly impacting energy density, power density, and cycling lifetime. However, ion concentration in electrolyte is usually low (0.01 M to 1 M), while ion diffusion coefficient is extremely high (10^-6 cm^2/s), making characterization of this process extremely difficult. Conventional characterization techniques such as transmission electron microscopy, nuclear magnetic resonance, and synchrotron radiation have encountered significant challenges on this topic, leaving ion transport process inside working batteries largely unknown.Stimulated Raman Scattering microscopy (SRS) is a recently emerging imaging technique, offering a speed approximately 10^8 times faster than conventional Raman spectrometers. It provides extremely high concentration, time, and spatial resolution, along with high selectivity and non-invasiveness. In our study, SRS was employed for the first time to dynamically image ion depletion within batteries and the growth of lithium dendrites in situ, providing visualization and quantitative analysis of ion distribution in liquid electrolytes. A three-stage lithium deposition process is uncovered, corresponding to no depletion, partial depletion, and full depletion of lithium ions. Further analysis reveals a feedback mechanism between the lithium dendrite growth and heterogeneity of local ionic concentration on lithium metal electrode, which can be effectively suppressed by artificial solid electrolyte interphase.We further explored lithium dendrite growth in PEO solid polymer electrolyte, but found unexpected opposite behaviors in solid polymer electrolytes: concentration polarization can induce phase transformation in a PEO electrolyte, forming a new PEO-rich but salt-/plasticizer-poor phase at the lithium/electrolyte interface, as unveiled by SRS. The new phase has a significantly higher Young’s modulus (1–3 GPa) than a bulk polymer electrolyte (<1 MPa). We hereby propose a design rule for PEO electrolytes: their compositions should be near the boundary between single-phase and two-phase regions in the phase diagram so that the applied current can induce the formation of a mechanically rigid PEO-rich phase to suppress lithium whiskers.This study revealed the growth mechanism of lithium dendrites and proposed solutions to suppress metallic lithium dendrites. SRS offers unprecedented ability over conventional characterization tools in studying reaction mechanisms, and is going to play a crucial role in research fields such as batteries, supercapacitors, and catalysis in the future.

The Genomic Signature and Transcriptional Response of Metal Tolerance in Brown Trout Inhabiting Metal-Polluted Rivers.

Industrial pollution is a major driver of ecosystem degradation, but it can also act as a driver of contemporary evolution. As a result of intense mining activity during the Industrial Revolution, several rivers across the southwest of England are polluted with high concentrations of metals. Despite the documented negative impacts of ongoing metal pollution, brown trout (Salmo trutta L.) survive and thrive in many of these metal-impacted rivers. We used population genomics, transcriptomics, and metal burdens to investigate the genomic and transcriptomic signatures of potential metal tolerance. RADseq analysis of six populations (originating from three metal-impacted and three control rivers) revealed strong genetic substructuring between impacted and control populations. We identified selection signatures at 122 loci, including genes related to metal homeostasis and oxidative stress. Trout sampled from metal-impacted rivers exhibited significantly higher tissue concentrations of cadmium, copper, nickel and zinc, which remained elevated after 11 days in metal-free water. After depuration, we used RNAseq to quantify gene expression differences between metal-impacted and control trout, identifying 2042 differentially expressed genes (DEGs) in the gill, and 311 DEGs in the liver. Transcriptomic signatures in the gill were enriched for genes involved in ion transport processes, metal homeostasis, oxidative stress, hypoxia, and response to xenobiotics. Our findings reveal shared genomic and transcriptomic pathways involved in detoxification, oxidative stress responses and ion regulation. Overall, our results demonstrate the diverse effects of metal pollution in shaping both neutral and adaptive genetic variation, whilst also highlighting the potential role of constitutive gene expression in promoting metal tolerance.

Na3.5(MnVFeTi)0.5(PO4)3: A Multi‐Transition‐Metal‐Ion‐Engineered NASICON‐Type Cathodes for Sodium Ion Batteries

AbstractElectrochemically active Na‐superionic conductor (NASICON)‐type cathodes have the structural flexibility to include various transition elements, thus enabling high power outputs benefited by multi‐electron redox reactions. This study amalgamated multiple transition metal ions to construct a new NASICON‐type cathode i. e., carbon coated Na3.5(MnVFeTi)0.5(PO4)3 (NMVFTP/C) for Na‐ion batteries (NIBs). The NMVFTP/C cathode engineered in this study demonstrated stable Na+‐storage capacity, including long‐term cycling stability up to 4000 cycles at 3000 mA g−1 with 96 % capacity retention and a high‐rate output capacity of 85.16 mAh g−1 at 2500 mA g−1. To elucidate the ion transport process within the cathode, density functional theory modeling was employed. The low energy barrier for the diffusion of Na+ in the NMVFTP/C materials was proved to be a key factor supporting our material's superior electrochemical performances.

Photo‐activation of Tolane‐based Synthetic Ion Channel for Transmembrane Chloride Transport

AbstractWhile natural channels respond to external stimuli to regulate ion concentration across cell membranes, creating a synthetic version remains challenging. Here, we present a photo‐responsive uncaging technique within an artificial ion channel system, which activates the ion transport process from a transport‐inactive o‐nitrobenzyl‐based caged system. From the comparative ion transport screening, 1 b emerged as the most active transporter. Interestingly, its bis(o‐nitrobenzyl) derivative, i.e., protransporter 1 b′ was inefficient in transporting ions. Detailed transport studies indicated that compound 1 b is an anion selective transporter with a prominent selectivity towards chloride ions by following the antiport mechanism. Compound 1 b′ did not form an ion channel, but after the o‐nitrobenzyl groups were photocleaved, it released 1 b, forming a transmembrane ion channel. The channel exhibited an average diameter of 6.5±0.2 Å and a permeability ratio of . The geometry‐optimization of protransporter 1 b′ indicated significant non‐planarity, corroborating its inefficient self‐assembly. In contrast, the crystal structure of 1 b demonstrates strong self‐assembly via the formation of an intermolecular H‐bond. Geometry optimization studies revealed the plausible self‐assembled channel model and the interactions between the channel and chloride ion.

Photo-activation of Tolane-based Synthetic Ion Channel for Transmembrane Chloride Transport.

While natural channels respond to external stimuli to regulate ion concentration across cell membranes, creating a synthetic version remains challenging. Here, we present a photo-responsive uncaging technique within an artificial ion channel system, which activates the ion transport process from a transport-inactive o-nitrobenzyl-based caged system. From the comparative ion transport screening, 1 b emerged as the most active transporter. Interestingly, its bis(o-nitrobenzyl) derivative, i.e., protransporter 1 b' was inefficient in transporting ions. Detailed transport studies indicated that compound 1 b is an anion selective transporter with a prominent selectivity towards chloride ions by following the antiport mechanism. Compound 1 b' did not form an ion channel, but after the o-nitrobenzyl groups were photocleaved, it released 1 b, forming a transmembrane ion channel. The channel exhibited an average diameter of 6.5±0.2 Å and a permeability ratio of . The geometry-optimization of protransporter 1 b' indicated significant non-planarity, corroborating its inefficient self-assembly. In contrast, the crystal structure of 1 b demonstrates strong self-assembly via the formation of an intermolecular H-bond. Geometry optimization studies revealed the plausible self-assembled channel model and the interactions between the channel and chloride ion.

Releasing Preferentially Sequestered Na+ from Its Confinement by Beauvericin: A Single Water Molecule is the Accomplice.

Beauvericin (Bv) is a natural ionophore capable of transporting ions across biological membranes. Mass spectrometry and infrared spectroscopy show that Bv specifically captures sodium ions with a unique 6-fold coordination in its cavity, which illustrates how ions are carried through the membrane. But with no reports on how ions are released from Bv at the interface, a complete picture of the ion transport process has yet to be established. In this study, conformational changes of Bv complexes with alkali metal ions upon hydration were investigated using infrared spectroscopy and computational calculations. The addition of a single water molecule to Na+Bv pries the ion away from the 6-fold cavity to the amide face of the ionophore, evidence of the first step of ion release. In contrast, there is little impact on the other M+Bv complexes, with the ion bound to the three carbonyl groups on the amide face. Analysis of the carbonyl C═O and water OH stretching modes reveals the competition between ion-ionophore, ion-water, and water-ionophore interactions and demonstrates how water actively participates in ion transport by initiating ion release from the ionophore.

Two-dimensional nanofluidic channels with Janus heterostructures for highly rectified ion transport

The integration of two-dimensional (2D) nanochannels with differing properties presents a promising avenue for mimicking ion transport processes in biological systems. In this study, a bioinspired Janus nanochannel membrane (BJNM) is developed by incorporating intercalated montmorillonite (MMT) and graphene oxide (GO) nanosheets. The asymmetric characteristics in chemical composition, structure, and charge distribution confer the BJNM with the ability to rectify ion transport, as evidenced by nonlinear current-voltage relationships. Through optimization of the electrolyte solution and applied voltage range, a notable rectification ratio of 40.9 is achieved. The underlying mechanism of ion rectification is explored through numerical simulations, highlighting the significance of 2D heterojunctions. These findings provide valuable insights for the design of nanofluidic systems tailored for precise ion transport, biosensing applications, and energy conversion processes.

An ion soft-landing apparatus for ion transport study with surface potential measurement.

An apparatus for explorations of ion transport in a medium and across an interface has been constructed. The ion soft-landing technique is used to deposit low-energy ions onto a pre-adsorbed medium layer on a metal substrate. The designed low-energy ion source can produce a mass-filtered ion beam with tens of nanoampere from solid sources such as bulk metals and salts. The kinetic energy of the ion beam can be lower than 1.0eV, enabling the ions to be soft-landed onto the medium at the surface. A Kelvin probe with a resolution of less than 32 mV is incorporated to measure the surface potential (SP) variation of the ion-landed sample to monitor the ion transport process in the medium. Temperature-programmed SP measurements on an Ag+-adsorbed ice film prepared on Pt(111) reveal that the temperature threshold for the Ag+-induced SP change of the ice film is about 110K. The apparatus performance demonstrates its potential in studies of ion transport and related phenomena at both macroscopic and microscopic levels.

Very Large and Long-lasting Anisotropies Caused by Sunward Streaming Energetic Ions: Solar Orbiter and STEREO A Observations

The anisotropy of energetic particles provides essential information to help resolve the underlying fundamental physics of their spatial distributions, injection, acceleration, and transport processes. In this work, we report an energetic ion enhancement that is characterized by very large and long-lasting anisotropies observed by STEREO A and Solar Orbiter, which are nearly aligned along the same nominal Parker spiral. This ion enhancement appears at the rising phase of a widespread solar energetic particle event that was associated with the farside coronal mass ejection on 2022 February 15. According to our analysis, the long-lasting anisotropy resulted from the continuous injection of energetic ions from a well-connected particle source located beyond the STEREO A’s orbit. Solar Orbiter also observed an interval of very large anisotropy dominated exclusively by sunward streaming ions but with the additional implication that it detected the very early phase of ion injections onto magnetic field lines that newly connected to the particle source, which is likely the first reported event of this kind. These results further illustrate how energetic particle anisotropy information, in particular from multiple observer locations, can be used to disentangle the sources and transport processes of energetic ions, even when their heliospheric context is not simple.

Site Disorder Drives Cyanide Dynamics and Fast Ion Transport in Li6PS5CN.

Halide argyrodite solid-state electrolytes of the general formula Li6PS5 X exhibit complex static and dynamic disorder that plays a crucial role in ion transport processes. Here, we unravel the rich interplay between site disorder and dynamics in the plastic crystal argyrodite Li6PS5CN and the impact on ion diffusion processes through a suite of experimental and computational methodologies, including temperature-dependent synchrotron powder X-ray diffraction, AC electrochemical impedance spectroscopy, 7Li solid-state NMR, and machine learning-assisted molecular dynamics simulations. Sulfide and (pseudo)halide site disorder between the two anion sublattices unilaterally improves long-range lithium diffusion irrespective of the (pseudo)halide identity, which demonstrates the importance of site disorder in dictating bulk ionic conductivity in the argyrodite family. Furthermore, we find that anion site disorder modulates the presence and time scales of cyanide rotational dynamics. Ordered configurations of anions enable fast, quasi-free rotations of cyanides that occur on time scales of 1011 Hz at T = 300 K. In contrast, we find that cyanide dynamics are slow or frozen in Li6PS5CN when site disorder between the cyanide and sulfide sublattices is present at T = 300 K. We rationalize the observed differences in cyanide dynamics in the context of elastic dipole interactions between neighboring cyanide anions and local strain induced by the configurations of site disorder that may impact the energetic landscape for cyanide rotational dynamics. Through this study, we find that anion disorder plays a decisive role in dictating the extent and time scales of both lithium ion and cyanide dynamics in Li6PS5CN.

Small-Molecule Mixed Ionic-Electronic Conductors for Efficient N-Type Electrochemical Transistors: Structure-Function Correlations.

The fundamental challenge in electron-transporting organic mixed ionic-electronic conductors (OMIECs) is simultaneous optimization of electron and ion transport. Beginning from Y6-type/U-shaped non-fullerene solar cell acceptors, we systematically synthesize and characterize molecular structures that address the aforementioned challenge, progressively introducing increasing numbers of oligoethyleneglycol (OEG; g) sidechains from 1 g to 3 g, affording OMIECs 1gY, 2gY, and 3gY, respectively. The crystal structure of 1gY preserves key structural features of the Yn series: a U-shaped/planar core, close π-π molecular stacking, and interlocked acceptor groups. Versus inactive Y6 and Y11, all of the new glycolated compounds exhibit mixed ion-electron transport in both conventional organic electrochemical transistor (cOECT) and vertical OECT (vOECT) architectures. Notably, 3gY with the highest OEG density achieves a high transconductance of 16.5 mS, an on/off current ratio of ~106, and a turn-on/off response time of 94.7/5.7 ms in vOECTs. Systematic optoelectronic, electrochemical, architectural, and crystallographic analysis explains the superior 3gY-based OECT performance in terms of denser ngY OEG content, increased crystallite dimensions with decreased long-range crystalline order, and enhanced film hydrophilicity which facilitates ion transport and efficient redox processes. Finally, we demonstrate an efficient small-molecule-based complementary inverter using 3gY vOECTs, showcasing the bioelectronic applicability of these new small-molecule OMIECs.

Small‐Molecule Mixed Ionic‐Electronic Conductors for Efficient N‐Type Electrochemical Transistors: Structure‐Function Correlations

The fundamental challenge in electron‐transporting organic mixed ionic‐electronic conductors (OMIECs) is simultaneous optimization of electron and ion transport. Beginning from Y6‐type/U‐shaped non‐fullerene solar cell acceptors, we systematically synthesize and characterize molecular structures that address the aforementioned challenge, progressively introducing increasing numbers of oligoethyleneglycol (OEG; g) sidechains from 1g to 3g, affording OMIECs 1gY, 2gY, and 3gY, respectively. The crystal structure of 1gY preserves key structural features of the Yn series: a U‐shaped/planar core, close π‐π molecular stacking, and interlocked acceptor groups. Versus inactive Y6 and Y11, all of the new glycolated compounds exhibit mixed ion‐electron transport in both conventional organic electrochemical transistor (cOECT) and vertical OECT (vOECT) architectures. Notably, 3gY with the highest OEG density achieves a high normalized transconductance of 25.29 S cm‐1, an on/off current ratio of ~106, and a turn‐on/off response time of 94.7/5.7 ms in vOECTs. Systematic optoelectronic, electrochemical, architectural, and crystallographic analysis explains the superior 3gY‐based OECT performance in terms of denser ngY OEG content, increased crystallite dimensions with decreased long‐range crystalline order, and enhanced film hydrophilicity which facilitates ion transport and efficient redox processes. Finally, we demonstrate an efficient small‐molecule‐based complementary inverter using 3gY vOECTs, showcasing the bioelectronic applicability of these new small‐molecule OMIECs.