Ion Mobility Research Articles

Synthesis and utilization of mixed-metal (Zn/Cd) metal–organic frameworks for ultra-trace determination of diazinon and ethion via ion mobility spectrometry

Synthesis and utilization of mixed-metal (Zn/Cd) metal–organic frameworks for ultra-trace determination of diazinon and ethion via ion mobility spectrometry

Achieving High Performance with Less Energy Consumption: Intermittent Ultrasonic-Mediated Operation Mode for Fe/V Non-Aqueous Redox Flow Battery

Deep eutectic solvents (DESs) have attracted much attention as sustainable electrolytes for redox flow batteries. Despite the tremendous advantages of DES-based electrolytes, their high viscosity property has a negative effect on their mass transfer, limiting current density and power density. The ultrasonic effect has been demonstrated as an efficient strategy to improve mass transfer characteristics. Incorporating ultrasonic waves into a deep eutectic solvent (DES) electrolyte enhances the mobility of redox-active ions, thereby accelerating the reaction dynamics of the Fe(III)/Fe(II) redox pair. This enhancement makes it suitable for use in non-aqueous electrolyte-based redox flow batteries. However, it is necessary to consider the loss of ultrasonic on the internal structure of the battery, as well as the loss of battery component materials and ultrasonic energy consumption in practical applications. Moreover, the continuous extension of the duration of ultrasonic action not only hardly leads to a more significant improvement of the battery performance, but is also detrimental to the energy and economic savings. Herein, intermittent ultrasound is used to overcome the quality transfer problem and reduce the operating cost. Good electrochemical performance enhancement is maintained with a roughly 50% reduction in energy consumption values. The mechanism as well as the visualization of the pulsed ultrasonic field on each half cell has been envisaged through fundamental characterization. Finally, the feasibility of interrupted ultrasonic activation applied to Fe/V RFB using DES electrolytes has been demonstrated, demonstrating similar behavior with continuous ultrasonic operation. Therefore, the interrupted ultrasonic field has been found to be a more effective operation mode in terms of energy cost, avoiding alternative undesirable effects like overheating or corrosion of materials.

Investigation of the effect of crystal size on the piezoelectric features of lead-free barium titanate ceramic using molecular dynamics simulation.

This study investigated the piezoelectric properties of BaTiO3 ceramics with different sizes through molecular dynamics simulations. The results show that all samples reached thermal equilibrium at 300K and equilibrium in potential energy within 10ns, confirming effective equilibration. As the size of the ceramics increased, the mean square displacement and diffusion coefficients decreased from 0.217 and 0.0034 to 0.1934 Å2 and 0.003 Å2/ns, attributed to a more uniform microstructure with fewer defects, resulting in reduced ion mobility. Furthermore, saturation polarization, residual polarization, and coercive field values increased from 0.35, 0.1, and 0.175 to 0.42 C/m2, 0.16 C/m2, and 0.282 MV/m, respectively, with increasing sample size, highlighting enhanced polarization responses due to a greater volume of ferroelectric material. Larger barium titanate (BaTiO3) crystals can have better polarization due to more domains aligning, but they may not deform as much (lower strain) because the walls among those domains can't move freely. While improved domain alignment contributed to higher polarization, the increased stress can restrict the mobility of the domain walls. These findings provided valuable insights into the size-dependent behavior of BaTiO3 ceramics, essential for optimizing their applications in electronic devices and sensors. The study underscored the importance of understanding microstructural effects on material properties for future advancements in ferroelectric technology.

Evaluation of flavor characteristics in Chinese wheat flour paste using electronic-nose, electronic-tongue, and headspace-gas chromatography-ion mobility spectrometry at different fermentation stages.

Wheat flour paste is a typical Chinese fermented food, valued for its distinct flavors and health benefits. However, evidence regarding volatile organic compounds (VOCs) in Chinese wheat flour paste is limited. This study aims to examine the effect of fermentation on the VOCs and their physicochemical properties. Chinese wheat flour paste fermented at different stages was characterized using headspace gas chromatography ion-mobility spectrometry (HS-GC-IMS) with an electronic nose (E-nose) and an electronic tongue (E-tongue). The results revealed that around 76 VOCs were found in Chinese wheat flour paste from all stages of fermentation. These included esters, alcohols, aldehydes, ketones, acids, furans, and pyrazines. The E-tongue and E-nose analyses also showed high responses for saltiness, umami, WIW, and W5S. The fermentation process changed the color of the wheat flour paste, and the taste, and smell parameters. Principal component analysis (PCA) showed that taste parameters were positively associated with the volatile flavor profile detected in wheat flour paste. Partial least squares discriminant analysis also identified 28 VOCs as distinct flavor metabolites across fermentation stages. At the 'after ripening' (AR) and 'sterilization' (S) stages of wheat flour paste fermentation there were strong umami and salty flavors, with minimal sour and sweet notes in comparison with the other stages. These stages were characterized by elevated terpene concentrations, inorganic sulfides, and key flavor enhancers such as 2-hexanol and propyl sulfide. Headspace gas chromatography ion-mobility spectrometry and E-nose technologies are recommended for a more precise assessment of volatile changes during fermentation. The findings indicate that the 'sterilization' stage of wheat flour paste fermentation is optimal for achieving the required flavor profile. © 2024 Society of Chemical Industry.

Impact of Ion Migration on the Performance and Stability of Perovskite‐Based Tandem Solar Cells

AbstractThe stability of perovskite‐based tandem solar cells (TSCs) is the last major scientific/technical challenge to be overcome before commercialization. Understanding the impact of mobile ions on the TSC performance is key to minimizing degradation. Here, a comprehensive study that combines an experimental analysis of ionic losses in Si/perovskite and all‐perovskite TSCs using scan‐rate‐dependent current–voltage (J–V) measurements with drift‐diffusion simulations is presented. The findings demonstrate that mobile ions have a significant influence on the tandem cell performance lowering the ion‐freeze power conversion efficiency from >31% for Si/perovskite and >30% for all‐perovskite tandems to ≈28% in steady‐state. Moreover, the ions cause a substantial hysteresis in Si/perovskite TSCs at high scan speeds (400 s−1), and significantly influence the performance degradation of both devices through internal field screening. Additionally, for all‐perovskite tandems, subcell‐dominated J–V characterization reveals more pronounced ionic losses in the wide‐bandgap subcell during aging, which is attributed to its tendency for halide segregation. This work provides valuable insights into ionic losses in perovskite‐based TSCs which helps to separate ion migration‐related degradation modes from other degradation mechanisms and guides targeted interventions for enhanced subcell efficiency and stability.

On the Thermal Conductivity and Local Lattice Dynamical Properties of NASICON Solid Electrolytes.

The recent development of solid-state batteries brings them closer to commercialization and raises the need for heat management. The NASICON material class (Na1+xZr2PxSi3-xO12 with 0 ≤ x ≤ 3) is one of the most promising families of solid electrolytes for sodium solid-state batteries. While extensive research has been conducted to improve the ionic conductivity of this material class, knowledge of thermal conductivity is scarce. At the same time, the material's ability to dissipate heat is expected to play a pivotal role in determining efficiency and safety, both on a battery pack and local component level. Dissipation of heat, which was, for instance, generated during battery operation, is important to keep the battery at its optimal operating temperature and avoid accelerated degradation of battery materials at interfaces. In this study, the thermal conductivity of NaZr2P3O12 and Na4Zr2Si3O12 is investigated in a wide temperature range from 2 to 773 K accompanied by in-depth lattice dynamical characterizations to understand underlying mechanisms and the striking difference in their low-temperature thermal conductivity. Consistently low thermal conductivities are observed, which can be explained by the strong suppression of propagating phonon transport through the structural complexity and the intrinsic anharmonicity of NASICONs. The associated low-frequency sodium ion vibrations lead to the emergence of local random-walk heat transport contributions via so-called diffusons. In addition, the importance of lattice dynamics in the discussion of ionic transport as well as the relevance of bonding characteristics typical for mobile ions on thermal transport, is highlighted.

Prospects of Improving Efficiency and Stability of Hybrid Perovskite Solar Cells by Alumina Ultrathin Films.

Over the last few years, the influence of low temperature (≤80 °C) and, in particular, of room temperature, atomic layer deposited alumina (ALD-Al2O3) on the properties of the underlying hybrid perovskites of different compositions and on the efficiency and stability of the corresponding perovskite solar cells (PSCs) is extensively investigated. The main conclusion is that most probably thanks to the presence of intrinsic defect states in the ALD-Al2O3 and in the perovskite layers, charge transfer and neutralization are possible and the entire lifetime of the PSCs is thus improved. Moreover, the migration of mobile ions between the layers is blocked by the ALD-Al2O3 layer and thus the occurrence of hysteresis in the current density-voltage characteristics of the PSCs is suppressed. Considering the uniform and nondestructive surface coverage, low thermal budget, small amount of material required, and short duration of the established ALD-Al2O3 deposition on top of hybrid perovskites, this additional, but fully solar cell technology-compatible, process step is most likely the most effective, cheapest, and fastest way to improve the efficiency and long-term stability of PSCs and thus increase their marketability.

Abstract 4131674: ADP-Ribosylation In a Mouse Model of Atherosclerosis: a Potential Novel Link Between Dyslipidemia and Inflammation in Cardiovascular Disease

Background: Inflammation and lipid accumulation are major features of atherosclerosis, a leading cause of death and morbidity worldwide. Our previous study recognized ADP-ribosylation, a post-translational modification, as a novel regulator of macrophage activation. We also have established mass spectrometry-based ADP-ribosylation proteomics. Using this technology, we evaluated the completely uncharacterized role of ADP-ribosylation in atherogenesis. We hypothesized that ADP-ribosylated proteins circulate from liver, accumulate in aorta and promote atherogenesis. Methods and Results: We harvested the aorta, liver, and plasma of LDL receptor-deficient ( Ldlr -/- ) mice that were on a regular chow or high-fat diet for 3 or 6 months (n=40/condition). To increase ADP-ribosyl peptide signals in the aorta, we applied our novel recently optimized ion mobility mass spectrometry strategy to generate ADP-ribosylation proteomics data. We analyzed 160 mice aortas and identified 3 APOA1 and 3 APOE ADP-ribosylated peptides in both the aorta and the liver (Fig. A). In addition, these peptides were differentially abundant in the aorta of HFD-fed mice, compared to controls (i.e, APOA1 ARPALEDLR peptide relative abundance (Fig. B)). Using the same mouse plasma, we then validated the presence of ADP-ribosylated APOA1 and ADP-ribosylated APOE in HDL and chylomicron/VLDL/LDL fractions (Western blot), respectively. This finding indicates that classical apolipoproteins circulate as ADP-ribosylated forms, representing a completely novel class of modified apolipoproteins. Immunohistochemistry confirmed the enrichment of aortic lesions in macrophages and ADP-ribosylation signal (5-fold increase, p=0.0006). Conclusions: This work provides the first in vivo evidence that ADP-ribosylation occurs in atherosclerotic lesions, which may originate from the liver via circulating blood (Fig. C). Future studies will examine whether ADP-ribosylation of apolipoproteins, specifically APOA1, alters anti-atherogenic functions of HDL.

Real-Time Estimation of CO2 Absorption Capacity Using Ionic Conductivity of Protonated Di-Methyl-Ethanolamine (DMEA) and Electrical Conductivity in Low-Concentration DMEA Aqueous Solutions

The present study investigates the real-time estimation of CO2 absorption capacity (CAC) based on the electrical conductivity (EC) of low-concentration di-methyl-ethanolamine (DMEA) solutions (0.1–0.5 M). CO2 absorption experiments are conducted to measure the variation in CAC and EC during CO2 absorption, revealing a strong correlation between the two properties. The ionic conductivity of DMEAH+ formed during absorption is calculated to be 53.1 S·cm2/(mol·z), which is found to be larger than that of TEAH+ and MDEAH+. This can be attributed to the smaller molar mass and higher ionic mobility of DMEAH+. A significant finding is that the measured EC (ECM) of the DMEA solutions consistently demonstrates a lower value than the theoretically predicted value. This discrepancy is due to the larger ionic size of DMEAH+, which results in a reduction in the real mean ionic activity coefficient. This effect becomes more pronounced with increasing DMEA concentration. Consequently, a higher CAC is required to produce the same change in EC at higher amine concentrations. Based on these findings, an empirical equation is devised to estimate CAC from ECM in solutions of constant DMEA concentration. This equation will be employed as a practical approach for the in situ monitoring of CO2 absorption using DMEA aqueous solution.

Formation of Sodium Chloride on the Surface of Sulfate-Rich Gobi Desert Salt in Response to Water Adsorption.

Dust storms in arid regions transport desert salts and dust, affecting geochemical processes, atmospheric chemistry, climate, and human health. This study examines how the gas-salt interface composition of desert salt changes with varying relative humidity (RH), using ambient pressure X-ray photoelectron spectroscopy (APXPS), near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, and molecular dynamics (MD) simulations. Ion chromatography analysis of desert salt indicates it is predominantly composed of sulfate, sodium, and magnesium ions, with traces of calcium, chloride, nitrate, and potassium ions. APXPS and NEXAFS surface analyses show that, at 0% RH, the gas-salt interface primarily features Na2SO4, with smaller amounts of MgSO4 and a trace of NaCl on the top layers. As humidity increases, the composition at the gas-salt interface changes, notably with Mg2+ binding to SO4 2- ions and a dominant NaCl formation throughout the studied surface depth. This shift indicates a transition from a sulfate- to a chloride-rich surface as humidity increases, contradicting MD simulations that predicted that on salt crystals covered by a submonolayer of water with electrolytes, chloride ions migrate toward the liquid-solid interface. This discrepancy indicates that other factors, like enhanced ionic mobility at grain boundaries, might drive the accumulation of chloride ions at the gas interface. The study emphasizes the crucial role of adsorbed water in ion migration and surface composition transformation of desert salts, affecting geochemical processes in arid regions.

PH-controlled-ion-mobility of Laponite-phosphate dispersion for physical hydrogel with improved mechanical properties and sensitivity to CO2

Self-assembled physical nanocomposite hydrogels based on bio-based poly(itaconic acid) and Laponite® nanoclays were prepared and tested as possible CO2 sensors in smart food packaging. The structure and mechanical properties of the fabricated hydrogels were controlled by changing the initial pH of the aqueous Laponite® dispersions stabilised by tetrasodium pyrophosphate. The dispersions were studied by SAXS and analysed using circular disc and fractal model to determine clay agglomeration tendency. Sodium and pyrophosphate ions mobility was investigated by 23Na and 31P 1D as well as spin-spin relaxation times T2 NMR measurements. The rheological behaviour of the produced hydrogels was studied by oscillatory shear measurements. It was found that decreasing the pH of the Laponite® nanodispersions up to 8 increases the strength of the physical interactions between the nanoclays, dispersant, and polyelectrolyte chains, which enables production of dimensionally stable and mechanically robust hydrogels. Their potential application as the CO2-sensitive matrix for construction of environmentally friendly colorimetric sensors was demonstrated showing the CO2 sorption capacity of 0.07 mmol CO2/g. A prototype device of hydrogel sensor was built and tested in a food packaging application to monitor the plum fruit respiration processes.

Carbon-Encapsulated Bimetallic Fe-W-Based Selenides with Abundant Heterogeneous Conductive Network for Superior Potassium Ion Storage.

Potassium-ion batteries (KIBs) are one of the most promising alternatives to lithium-ion batteries (LIBs) due to their high ion mobility, abundant resources, and low cost. However, the problems of low capacity and poor cycling stability of KIBs remain unsolved; therefore, it is crucial to explore alternative electrode materials suitable for reversible insertion and extraction of K+. Herein, carbon-encapsulated Fe3Se4/WSe2 microsphere material assembled from nanosheets with abundant heterogeneous interfaces and expanded interlayer spacing (denoted as FWSC) is designed as an anode material for superior potassium ion storage. The microspheres assembled from nanosheets, the outer carbon coating, and the expanded layer spacing can expose more active sites and improve the electronic conductivity and structural stability of the material. The abundant heterogeneous conductive network not only improves the conductivity of the material but also enhances the reversibility of the electrochemical reaction. As a result, the FWSC exhibits outstanding cycling stability, excellent rate performance (the capacity retention is 53% when the current density is from 0.5 to 1.0 A g-1), and stable long-term cycle performance (a capacity of 209 mAh g-1 at 1.0 A g-1 over 1000 cycles).

Modified Debye-Hückel-Onsager theory for electrical conductivity in aqueous electrolyte solutions: Account of ionic charge nonlocality.

This paper presents a mean field theory of electrolyte solutions, extending the classical Debye-Hückel-Onsager theory to provide a detailed description of the electrical conductivity in strong electrolyte solutions. The theory systematically incorporates the effects of ion specificity, such as steric interactions, hydration of ions, and their spatial charge distributions, into the mean-field framework. This allows for the calculation of ion mobility and electrical conductivity, while accounting for relaxation and hydrodynamic phenomena. At low concentrations, the model reproduces the well-known Kohlrausch's limiting law. Using the exponential (Slater-type) charge distribution function for solvated ions, we demonstrate that experimental data on the electrical conductivity of aqueous 1:1, 2:1, and 3:1 electrolyte solutions can be approximated over a broad concentration range by adjusting a single free parameter representing the spatial scale of the nonlocal ion charge distribution. Using the fitted value of this parameter at 298.15K, we obtain good agreement with the available experimental data when calculating electrical conductivity across different temperatures. We also analyze the effects of temperature and electrolyte concentration on the relaxation and electrophoretic contributions to total electrical conductivity, explaining the underlying physical mechanisms responsible for the observed behavior.

Compact Plasma Ionization for Ion Mobility Spectrometry Using a 4.3 MHz Miniature Tesla Coil.

In this study, a low-cost 4.3 MHz plasma ionization source for ion mobility spectrometry (IMS), utilizing a miniaturized Tesla coil, is presented. This compact design, combined with a 3D printed cyclic olefin copolymer (COC) housing, delivers a stable and directed plasma suitable for ionization in IMS applications. The 3D printed housing ensures chemical resistance and low off-gassing, which are crucial for maintaining sample integrity. The Tesla coil produces a consistent sine wave at 4.3 MHz, and when connected to stainless steel screw electrodes it generates a stable plasma capable of ionizing analytes such as limonene, MTBE, nicotine, 2-octanone, and propofol. Measurements were conducted in both positive and negative ion modes. The results demonstrate the Tesla coil's effectiveness as a low-cost and reliable ionization source for IMS, offering comparable performance to traditional Ni63 β-emitters. This advancement in plasma ionization technology could facilitate more accessible and flexible IMS systems for diverse analytical applications. The integration of 3D printing in the development of this ionization source underscores the potential for customized, low-cost analytical instrumentation, promoting innovation in laboratory environments and commercial applications.

A Comparison of the Impacts of Different Drying Methods on the Volatile Organic Compounds in Ginseng

Ginseng (Panax ginseng C. A. Meyer) is a valuable plant resource which has been used for centuries as both food and traditional Chinese medicine. It is popular in health research and markets globally. Fresh ginseng has a high moisture content and is prone to mold and rot, reducing its nutritional value without proper preservation. Drying treatments are effective for maintaining the beneficial properties of ginseng post-harvest. In this study, we investigated the effects of natural air drying (ND), hot-air drying (HAD), vacuum drying (VD), microwave vacuum drying (MVD), and vacuum freeze drying (VFD) on volatile organic compounds (VOCs) in ginseng. The results showed that the MVD time was the shortest, followed by the VFD, VD, and HAD times, whereas the ND time was the longest, but the VFD is the most beneficial to the appearance and color retention of ginseng. A total of 72 VOCs were obtained and 68 VOCs were identified using the five drying methods based on gas chromatography–ion mobility spectrometry (GC-IMS) technology, including 23 aldehydes, 19 alkenes, 10 alcohols, 10 ketones, 4 esters, 1 furan, and 1 pyrazine, and the ND method was the best for retaining VOCs. GC-IMS fingerprints, principal component analysis (PCA), Euclidean distance analysis, partial least squares discriminant analysis (PLS-DA), and cluster analysis (CA) can distinguish ginseng from different drying methods. A total of 29 VOCs can be used as the main characteristic markers of different drying methods in ginseng. Overall, our findings provide scientific theoretical guidance for optimizing ginseng’s drying methods, aromatic health effects, and flavor quality research.

2D Graphene‐Like Carbon Coated Solid Electrolyte for Reducing Inhomogeneous Reactions of All‐Solid‐State Batteries

AbstractRecent studies have identified an imbalance between the electronic and ionic conductivities as the drivers of inhomogeneous reactions in composite cathodes, which cause the rapid degradation of all‐solid‐state battery (ASSB). To mitigate localized overcharge and utilize isolated active materials, the study proposes the coating of an argyrodite‐type Li6PS5Cl solid electrolyte (SE) with graphene‐like carbon (GLC@LPSCl), a 2D conductive material, to offer a continuous three‐dimensionally connected electron pathway within the composite cathode to facilitate ion mobility and promote homogeneous reactions. Despite reducing the content of the conducting agent, it is observed that the GLC@LPSCl cell exhibits high initial Coulombic efficiency and discharge capacity, reducing the inhomogeneous reactivity after 200 cycles compared with when ordinary conductive agents are deployed. Additionally, the presence of GLC@LPSCI surface suppresses the interfacial reaction between SE–cathode material, thus imparting the cell with excellent capacity retention (≈90%) after 200 cycles. Furthermore, the cell performance improves even after a fourfold increase in the cathode loading amount, demonstrating the criticality of a well‐developed continuous electron pathway to cell performance and highlighting the key role of ensuring a balance between the electron and ion conductivities in the development of high‐energy‐density and high‐power ASSBs.

Analysis of the ion mobility spectra of chloroacetophenone, tris(2-chloroethyl)amine, and methanethiol

Objectives. To determine the ion mobilities of chloroacetophenone, tris(2-chloroethyl)amine, and methanethiol; the structure of ions corresponding to characteristic signals; the detection limits of chloroacetophenone, tris(2-chloroethyl)amine, and methanethiol with the Kerber-T ion drift detector and the Segment automatic stationary gas detector.Methods. Ion mobility spectrometry was used in order to determine the ion mobilities and detect analytes. The enthalpies of reactions of ion formation were calculated using the ORCA 4.1.1 software by means of the B3LYP density functional method with the 6-31G(d,p) basis set.Results. The ion mobilities of chloroacetophenone, tris(2-chloroethyl)amine, and methanethiol were determined. A method for recording ion mobility spectra and their mathematical processing was developed. The dependencies of the change in ion mobility spectra on the analyte concentration were also studied. Possible mechanisms were proposed for the formation of the ion mobility spectra observed, in accordance with the ionization features of chloroacetophenone, tris(2-chloroethyl)amine, and methanethiol. The enthalpies of ion formation were calculated. The ionization schemes of the compounds were shown. The generalized results of experimental studies were presented, as were the features of compound identification taking into account the structure of the spectra, the concentrations of substances, and the detection conditions.Conclusions. Characteristic signals of chloroacetophenone, tris(2-chloroethyl)amine, and methanethiol were identified. All studied hazardous substances can be detected with an ion mobility spectrometer at concentrations at the ppm level. The following detection limits of the substances were determined with the Segment gas detector: chloroacetophenone, 245 mg/m3; tris(2-chloroethyl)amine, 0.01 mg/m3; and methanethiol, 0.8 mg/m3.

Ion Mobility QTOF-MS Untargeted Lipidomics of Human Serum Reveals a Metabolic Fingerprint for GNE Myopathy.

GNE myopathy, also known as hereditary inclusion body myopathy (HIBM), is a rare genetic muscle disorder marked by a gradual onset of muscle weakness in young adults. GNE myopathy (GNEM) is caused by bi-allelic variants in the UDP-N-acetylglucosamine 2-epimerase (UDP-GlcNAc 2-epimerase)/N-acetylmannosamine kinase (ManNAc kinase) gene (GNE), clinically resulting in the loss of ambulation within 10-20 years from the onset of the initial symptoms. The disease's mechanism is poorly understood and non-invasive biomarkers are lacking, hindering effective therapy development. Based on the available evidence, we employed a lipidomic approach to study the serum lipid profile of GNE patients. The multivariate statistical analysis revealed a downregulation of carnitines, as well as of lysophosphatidylcholines, in sera samples derived from GNEM patients. Furthermore, we identified lower levels of sphingomyelins and, concomitantly, high levels of ceramides in serum samples from GNEM patients when compared to control samples derived from healthy donors. Moreover, the GNEM serum samples showed the upregulation of Krebs cycle intermediates, in addition to a decrease in oxaloacetic acid. The correlated data gathered in this study can offer a promising diagnostic panel of complex lipids and polar metabolites that can be used in clinic for GNEM in terms of a metabolic fingerprint measurable in a minimally invasive manner.

ProtonationDriven Polarization Retention Failure in Nano-Columnar Lead-Free Ferroelectric Thin Films.

Understanding microscopic mechanisms of polarization retention characteristics in ferroelectric thin films is of great significance for exploring unusual physical phenomena inaccessible in the bulk counterparts and for realizing thin-film-based functional electronic devices. Perovskite (K,Na)NbO3 is an excellent class of lead-free ferroelectric oxides attracting tremendous interest thanks to its potential applications to nonvolatile memory and eco-friendly energy harvester/storage. Nonetheless, in-depth investigation of ferroelectric properties of (K,Na)NbO3 films and the following developments of nano-devices are limited due to challenging thin-film fabrication associated with nonstoichiometry by volatile K and Na atoms. Herein, ferroelectric (K,Na)NbO3 films of which the atomic-level geometrical structures strongly depend on thickness-dependent strain relaxation are epitaxially grown. Nanopillar crystal structures are identified in fully relaxed (K,Na)NbO3 films to the bulk states representing a continuous reduction of switchable polarization under air environments, that is, polarization retention failures. Protonation by water dissociation is responsible for the humidity-induced retention loss in nano-columnar (K,Na)NbO3 films. The protonation-driven polarization retention failure originates from domain wall pinning by the accumulation of mobile hydrogen ions at charged domain walls for effective screening of polarization-bound charges. Conceptually, the results will be utilized for rational design to advanced energy materials such as photo-catalysts enabling ferroelectric tuning of water splitting.

Impact of Ionene Architecture on Ion Mobility

Impact of Ionene Architecture on Ion Mobility