High Ion Mobility Research Articles

Molecular dynamics insights on temperature and pressure effects on electroporation

Electroporation is a cell-level phenomenon caused by an ionic imbalance in the membrane, being of great relevance in various fields of knowledge. A dependence of the pore formation kinetics on the environmental conditions (temperature and pressure) of the cell membrane has already been reported, but further clarification regarding how these variables affect the pore formation/resealing dynamics and the transport of molecules through the membrane is still lacking. The objective of the present study was to investigate the temperature (288–348 K) and pressure (1–5000 atm) effects on the electroporation kinetics using coarse-grained molecular dynamics simulations. Results shown that the time for pore formation and resealing increased with pressure and decreased with temperature, whereas the maximum pore radius increased with temperature and decreased with pressure. This behavior influenced the ion migration through the bilayer, and the higher ionic mobility was obtained in the 288 K/1000 atm simulations, i.e., a combination of low temperature and (not excessively) high pressure. These results were used to discuss some experimental observations regarding the extraction of intracellular compounds applying this technique. This study contributes to a better understanding of electroporation under different thermodynamic conditions and to an optimal selection of processing parameters in practical applications which exploit this phenomenon.

Highly ordered nanotubular niobium oxide obtained by self-organizing anodization: A study of capacitive behavior

Transition metal oxide nanotubes such as niobium have attracted wide scientific attention due to their unique properties such as high ionic mobility and large specific surface area. This study investigates the capacitive behavior of nanotubular niobium oxide obtained under extremely mild anodization conditions, aiming its application in supercapacitors. The nanotubular niobium oxide was obtained by potentiostatic anodization at 90 V at room temperature, in a glycerol electrolyte containing 0.4 M NH 4 F and 0.9% H 2 O. Field Emission Gun Scanning Electron Microscopy analysis (FEG-SEM) was employed to perform morphological characterization. The capacitive behavior of the obtained material was investigated by cyclic voltammetry and galvanostatic charge/discharge in a three-electrode system. The neutral aqueous electrolyte used was 1 M Na 2 SO 4 , in a potential window from −0.2 to −1.2 V vs. Ag/AgCl and 1 M H 2 SO 4 as an acid aqueous electrolyte in a potential window from −0.25 to −0.75 V vs Ag/AgCl. The FEG-SEM images revealed the presence of a self-organized highly ordered nanotubular niobium oxide layer on niobium substrate. Appreciable capacitance values of 20 mF cm −2 and 103 mF cm −2 were achieved in Na 2 SO 4 and H 2 SO 4 electrolytes, respectively. This great capacitive response can be associated with a large surface area achieved through the nanostructured oxide layer as well as the morphology of vertically aligned nanotubes that promote a directional ions transport, which, consequently, improves the capacitive performance. Besides, the results showed a superior performance, in terms of capacitance modulus and stability, for nanotubular niobium oxide in H 2 SO 4 electrolytes. The results obtained in this study highlight the great potential of the self-organized highly ordered nanotubular niobium oxide for application as a supercapacitor electrode.

Ru- and Cl-Codoped Li3 V2 (PO4 )3 with Enhanced Performance for Lithium-Ion Batteries in a Wide Temperature Range.

Li3 V2 (PO4 )3 (LVP) is a promising cathode material for lithium-ion batteries, especially when used in a wide temperature range, due to its high intrinsic ionic mobility and theoretical capacity. Herein, Ru- and Cl-codoped Li3 V2 (PO4 )3 (LVP-Rux -Cl3 x ) coated with/without a nitrogen-doped carbon (NC) layer are synthesized. Among them, the optimized sample (LVP-Ru0.05 -Cl0.15 @NC) delivers remarkable performances at both room temperature and extreme temperatures (-40, 25, and 60°C), indicating temperature adaptability. It achieves intriguing capacities (49 mAh g-1 at -40°C, 128 mAh g-1 at 25°C, and 123 mAh g-1 at 60°C, all at 0.5 C), long cycle life (94% capacity retention after 2000 cycles at 25°C and 5 C), and high-rate capabilities (up to 20 C). The structural evolution features and capacity loss mechanisms of LVP-Ru0.05 -Cl0.15 @NC are further investigated using in situ X-ray diffraction (XRD) at different temperatures (-10, 25, and 60°C) during redox reactions. Theoretical calculations elucidate that Ru- and Cl-codoping can greatly improve the intrinsic diffusion coefficient of LVP by reducing its bandgap energy and lowering the energy barrier of lithium-ion diffusion. In "all-weather" conditions, the dual-element co-doping strategy is critical for increasing electrochemical performance.

POSS hybrid poly(ionic liquid) ionogel solid electrolyte for flexible lithium batteries

Traditional lithium-ion batteries based on liquid electrolytes cannot adapt to the increasing and various highly flexible requirements. In this work, a confinement-driven strategy has been developed to confine the ionic liquids in a polyhedral oligomeric silsesquioxanes (POSS) and poly(ethylene glycol) diacrylate (PEGDA) hybrid cross-linked poly(ionic liquid)s ionogel (POSS-CPIL-n), which endows this novel electrolyte superior flame retardancy and dramatically flexibility. The POSS-CPIL-n ionogel renders exceptional flexibility (bend, fold and twist) and desired mechanical properties (2.5 MPa). Advantageous for high dissociation of lithium salt, high ionic conductivity (2.5 mS cm−1 at 25 °C) and considerable lithium ion mobility (0.51) are provided. Thanks to the flexibility of ionogel electrolyte together with excellent thermal and electrochemical stability, the LiFePO4||Li cell based on POSS-CPIL-n exhibits significant rate performance and cycling stability, the capacity of the cell can reach to 100 mAh g−1 at 4 C and maintain a substantial discharge capacity of 160.5 mAh g−1 after 200 cycles at 0.2C. Furthermore, the soft-package assembled with POSS-CPIL-n can successfully charge a cell phone and continue to supply power stably even when the battery is exposed to the air, which indicates that POSS-CPIL-n has a promising potential application in high safety flexible electronic devices.

Layered iron dichalcogenides with high ion mobility and capacity as promising anode materials for alkali metal-ion batteries: A first-principles study

Developing high-performance anode materials remains a key challenge for alkali metal-ion batteries (AIBs). Benefiting from a high surface-to-bulk ratio, layered materials are promising candidates for anodes due to their potential high specific capacity and low ion transport resistance derived from the numerous ion storage sites and inherent open channels. In this work, we predict that the recently synthesized layered iron dichalcogenides, namely FeX2 (X = S, Se, Te), are suitable anode materials for AIBs through first-principles calculations. The results show that both the pristine and alkali-metalized FeX2 monolayers are structurally stable and present a metallic nature. In addition, the alkali metal-ions exhibit low diffusion barriers (0.15 eV for Li-ions, 0.08 eV for Na-ions, and 0.05 eV for K-ions) on FeX2 monolayers, which indicates that they possess a high ionic conductivity as well as an excellent rate capability and cycling performance. Besides, the calculated low open-circuit voltage values (0.39, 0.29, and 0.19 V vs. Na/Na+ for FeS2, FeSe2, and FeTe2, respectively) reveal that layered FeX2 materials are suitable to serve as anodes for sodium-ion batteries (SIBs). As a result, FeS2 and FeSe2 monolayers exhibit a high theoretical specific capacity (893.6 and 501.4 mAh g−1, respectively) for SIBs, while the theoretical volume-specific capacity of FeTe2 monolayer (2343.3 mAh cm−3) is around two times larger than that of standard commercial cells. Our findings suggest that these currently unexploited layered iron dichalcogenides could be potential high-performance anode materials for AIBs.

Exploiting Self-Association to Evaluate Enantiomeric Composition by Cyclic Ion Mobility-Mass Spectrometry.

The characterization of enantiomers is an important analytical challenge in the chemical and life sciences. Thorough evaluation of the purity of chiral molecules is particularly required in the pharmaceutical industry where safety concerns are paramount. Assessment of the enantiomeric composition is still challenging and time-consuming, meaning that alternative approaches are required. In this study, we exploit the formation of dimers as diastereomeric pairs of enantiomers to affect separation by high resolution cyclic ion mobility–mass spectrometry. Using the example of (R/S)-thalidomide, we show that even though this is not an enantiomer separation, we can determine which enantiomer is in excess and obtain quantitative information on the enantiomer composition without the need for a chiral modifier. Further examples of the approach are presented, including d/l-tryptophan and (R/S)-propanolol, and demonstrate the need for mobility resolving power in excess of 400 (CCS/ΔCCS).

Unravelling Charge Carrier Mobility in d0‐Metal‐based Spinels

AbstractEnabling high Mg ion mobility, spinel‐type materials are promising candidates for cathode or solid electrolyte applications. To elucidate the factors governing the observed high mobility of multivalent ions, periodic DFT calculations of various charge carriers (A=Li, Na, K, Mg, Ca, Zn and Al) in the ASc2S4 and ASc2Se4 spinel compounds were performed, resulting in the identification of a Brønsted‐Evans‐Polanyi‐type scaling relation for the migration barriers of the various charge carriers. Combining this scaling relation with the derivation of a descriptor, solely based on easily accessible observables, constitutes a conceptual framework to investigate ion mobility in d0‐metal‐based spinel chalcogenides with significantly reduced computational effort. This approach was exemplarily verified for various d0‐metal‐based spinel chalcogenide compounds AB2X4 (B=Sc, Y, Ga, In, Er and Tm; X=O, S and Se) and led to the identification of d0‐metal‐based CaB2O4 spinels as promising compounds possibly enabling high Ca ion mobility.

Influence of Sample Gas Humidity on Product Ion Formation in High Kinetic Energy Ion Mobility Spectrometry (HiKE-IMS).

High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) chemically ionize gaseous samples via reactant ions and separate the generated ions by their motion in a neutral gas under the influence of an electric field. Operation at reduced pressures of 10-40 mbar allows for reaching high reduced electric field strengths (E/N) of up to 120 Td. At these high E/N, the generated ions gain the namesake high kinetic energies, leading to a decrease in cluster size of the reactant ions by increasing the reaction rate of collision-induced cluster dissociation of hydrates. In positive ion polarity and in purified air, H3O+(H2O)n, NO+(H2O)n, and O2+•(H2O)p are the most abundant reactant ions. In this work, we investigate the effect of varying sample gas humidity on product ion formation for several model substances. Results show that increasing the sample gas humidity at high E/N of 120 Td shifts product ion formation from a charge transfer dominated reaction system to a proton transfer dominated reaction system. For HiKE-IMS operated at high E/N, the reduction in cluster size of reactant ions allows ionization of analytes with low proton affinity even at high relative humidity in the sample gas of RH = 75% at 303.15 K and 1013.25 hPa. In contrast to conventional IMS, where increasing the sample gas humidity inhibits ionization for various analytes, increasing sample gas humidity in HiKE-IMS operated at 120 Td is actually beneficial for ionization yield of most analytes investigated in this work as it increases the number of H3O+(H2O)n.

Unravelling the comparative metabolite fingerprints and therapeutic effects of diverse teas

The comparative metabolite fingerprinting and bioactivity of different teas viz. green tea, oolong tea, white tea, orthodox black tea, and Cut/crush, Tear and Curl (CTC) black tea as compared to unprocessed tea leaves (GTL) were elucidated. The fresh tender tea shoots collected from single location were processed into different tea forms and brewed homogenously. The mass fingerprinting analysis using ultra high performance liquid chromatography ion mobility quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-IMS) revealed substantial variability of key metabolites among different tea brews. Statistical analysis (Venn-diagram, Heatmap and PCA) has revealed significant variation in metabolites content among different teas. Catechins and caffeine were identified and quantified in all infusions using high-pressure liquid chromatography analysis. 2,2-diphenyl-1- picrylhydrazyl (DPPH) free radical scavenging assay, 2,2′-azino-bis (3 ethylbenzothiazoline-6-sulphonic acid (ABTS) radical cation decolourisation assay and ferric-reducing antioxidant power (FRAP) assay unveiled significant antioxidant potential by all the infusions. The results of α-glucosidase inhibition by different teas showed positive effects in management of postprandial hyperglycemia. The tea samples also unveiled significant results for nitric oxide inhibition in lipopolysaccharide-stimulated RAW 264.7 macrophages and cytotoxicity against A-549 and CT26.CL25 cancer cells. Hence, it has established that tea processing has substantial role on key metabolite composition and therapeutic potential of different tea infusions.

Development and application of a fast ultra-high performance liquid chromatography-trapped ion mobility mass spectrometry method for untargeted lipidomics

The alteration of lipid profile in biological specimens, such as plasma, mirrors abnormalities in their homeostasis and offers pivotal information for disease comprehension. Fast analytical methods are needed to highlight changes in plasma lipid profile and deliver rapid results. In this study we developed a fast reversed phase ultra high performance liquid chromatography-trapped ion mobility mass spectrometry (RP-UHPLC-TIMS-MS) method for untargeted lipidomics. A short, narrow-bore fully porous particle CSH column (50 mm × 2.1 mm, 1.7 µm) was used, and by selecting appropriate flow rate, temperature and gradient conditions, the total analysis time was reduced from 20 to 4 min. TIMS was operated in parallel accumulation serial fragmentation mode (PASEF) which allowed to select multiple precursors for MS/MS and separate co-eluting lipids based on their different mobility. Lipid annotation was performed by rule-based approach, comparison with LipidBlast spectral library and manual data curation, by taking into account class-specific fragmentation pattern, accurate mass, adduct form, retention behavior in RP and comparison of their collision cross-section (CCS) values for increased confidence. 306 unique lipids from 21 subclasses were annotated from 20 µL of plasma, while their concentration was estimated by class-specific deuterated internal standards. The analytical method was validated and finally applied to elucidate the alteration of plasma lipid profiles in a small cohort of amyotrophic lateral sclerosis (ALS) patients. Univariate and multivariate statistics evidenced significant differences with respect to control patients, particularly in the levels of ether linked lipids (PC-O, PE-O, PE-P and LPC-O), sphingolipids (Ceramides), and triacylglycerols, showing the usefulness of this fast approach in providing accurate and rapid results with respect to longer (≥15 min) untargeted UHPLC-HRMS methods.

Mass Spectrometry Based Identification of Novel HLA Class I Restricted Peptides in Merkel Cell Carcinoma

Highly polymorphic class I human leukocyte antigen (HLA‐I) molecules present endogenous peptides to CD8+ T cells, an essential part of immune regulation. This mechanism allows for the presentation of thousands of epitopes per allele and individual. Liquid chromatography‐mass spectrometry (LC‐MS/MS) is a high throughput method that can be utilized to identify endogenously processed and presented peptides. Merkel cell carcinoma (MCC) is a rare and aggressive form of neuroendocrine skin cancer. A major subtype of this cancer is caused by the Merkel cell Polyomavirus (MCPyV), so MCPyV+ MCC is an informative model system to explore virally derived cancer‐specific epitopes. MCC, however, often downregulates or eliminates HLA‐I antigen presentation to evade recognition by the immune system. We hypothesized that reversing the mechanisms of immune evasion will allow us to detect novel epitopes. Here, we used optimized LC‐MS/MS methods to characterize the immunopeptidome of MCC in a native and perturbed state. First, we compared the immunopeptidome of primary tumor samples and tumor‐derived MCC cell lines. Peptide identities presented on primary tumors and tumor‐derived cell lines overlapped by 50% or more, indicating that the tumor‐derived cell lines retain their innate tumor properties and are a useful model to study immune presentation in MCC. Next, we investigated mechanisms to restore HLA‐I presentation in MCC, such as IFNγ treatment and knockout or inhibition of components of the Polycomb repressive complex (PRC1.1). We found that IFNγ treatment increased peptide yield up to 8‐fold across seven cell lines while also increasing presentation on HLA‐B alleles. Using tandem mass tag labeling, we observed relative quantitative changes in the immunopeptidome of an MCPyV+ cell line when PRC1.1 components were knocked down. We discovered increased HLA‐I presentation upon USP7 inhibitor treatment in comparison to the control. In contrast to IFNγ treatment, USP7 inhibition did not alter the fraction of observed peptides assigned to alleles. Finally, use of High Field Asymmetric Ion Mobility Spectrometry (FAIMS) to analyze samples with reinstated HLA presentation enabled identification of a number of novel antigens, including three MCPyV viral epitopes. The immunogenicity of these viral peptides was determined by ELISpot assays with peripheral blood mononuclear cells (PBMCs). These findings can be translated into medical treatments for patients diagnosed with this cancer.

Considering the Role of Ion Transport in Diffuson‐Dominated Thermal Conductivity

AbstractNext‐generation thermal management requires the development of low lattice thermal conductivity materials, as observed in ionic conductors. For example, thermoelectric efficiency is increased when thermal conductivity is decreased. Detrimentally, high ionic conductivity leads to thermoelectric device degradation. Battery safety and design also require an understanding of thermal transport in ionic conductors. Ion mobility, structural complexity, and anharmonicity have been used to explain the thermal transport properties of ionic conductors. However, thermal and ionic transport are rarely discussed in direct comparison. Herein, the ionic conductivity of Ag+ argyrodites is found to change by orders of magnitude without altering the thermal conductivity. Thermal conductivity measurements and two‐channel lattice dynamics modeling reveal that the majority of Ag+ vibrations have a non‐propagating diffuson‐like character, similar to amorphous materials. It is found that high ionic mobility is not a requirement for diffuson‐mediated transport. Instead, the same bonding and structural traits that can lead to fast ionic conduction also lead to diffuson‐mediated transport. Bridging the fields of solid‐state ionics and thermal transport, it is proposed that a vibrational perspective can lead to new design strategies for functional ionic conducting materials. As a first step, the authors relate the so‐called Meyer–Neldel behavior in ionic conductors to phonon occupations.

Lithium‐Ion Battery Technology for Voltage Control of Perpendicular Magnetization

AbstractThe voltage control of magnetism is a promising path to the development of low‐power spintronic devices. Magneto‐ionics—exploiting voltage‐driven ion migration to control magnetism—has attracted interest because it can generate large magnetoelectric effects at low voltage. Here, the use of the solid‐state lithium‐ion battery technology for reversible voltage‐controlled switching between perpendicular and in‐plane magnetization states in a Co–Pt bilayer is demonstrated. Due to the small size and high mobility of lithium ions, small voltages produce an exceptionally high magnetoelectric coupling efficiency of at least 7700 fJ V–1 m–1 at room temperature. The magnetic switching effect is attributed to the modulation of spin‐orbit coupling at the Co–Pt interface when lithium ions migrate between a lithium storage layer (LiCoO2) and the magnetic interface across a lithium phosphorous oxynitride (LiPON) solid‐state electrolyte, which is corroborated by density functional theory calculations. Voltage control of magnetism in the battery structure does not show degradation over more than 500 voltage cycles, demonstrating promise for solid‐state lithium‐based magneto‐ionic devices.

Boosting the Ion Mobility in Solid Polymer Electrolytes Using Hollow Polymer Nanospheres as an Additive.

Solid polymer electrolytes (SPEs) possess improved thermal and mechanical stability as safe energy storage devices. However, their low ion mobilities and poor electrochemical stabilities still hinder the wide industrial application of SPEs. Herein, we introduce an SPE design that provides an enormous number of electrochemically stable pathways and space for lithium-ion transport, blending polymer (polydopamine) hollow nanospheres with an inactive inorganic template into a poly(ethylene oxide) (PEO) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) based SPE. Hollow silica acts as a template for polydopamine processing a large contact area with the polymer electrolyte, and the interface between the polymer electrolyte and hollow composite fillers provides amounts of ion transport channels. In addition, theoretical calculations reveal a strong adsorption between polydopamine and TFSI-, which suppresses the TFSI- motion and meanwhile facilitates the selective Li+ transport. The hollow polydopamine can serve as a versatile platform for anion trapping and has large compatible and stable depression for a well-defined ion transfer interface layer, forming a three-in-one nanocomposite for the enhancement of ionic conductivity with no sacrifice of the mechanical properties. Experimental data confirmed the high mobility of ions within the composite electrolyte with an ionic conductivity of 0.189 mS cm-1 in comparison to the SPE without additives (0.105 mS cm-1) at 60 °C. The mobility of the Li+ increases after adding the polymer-coated inorganic additives, associated with a noticeable enlargement of the electrochemical window. Furthermore, an all-solid-state Li/LiFePO4 battery with a hollow polydopamine nanoparticle-polymer composite electrolyte shows long life, high reversible capacity (134.9 mAh g-1), and high capacity retention (97.2%) after 205 cycles at 0.2 C.

Separation of disaccharide epimers, anomers and connectivity isomers by high resolution differential ion mobility mass spectrometry

Glycans are ubiquitous, structurally diverse molecules that have specific and general roles involving metabolism, structure, and cell-to-cell signaling. Functional specificity depends strongly on the complexity of structures that polysaccharides can adopt based on their subunit composition, length, extent of branching, glycosidic bond connectivity and anomeric configuration. However, a rapid and comprehensive characterization of glycan isomers can be challenging owing to limitations associated with their separation. Here, ten composition, anomeric and connectivity disaccharide isomers were separated and detected using high-resolution differential ion mobility-mass spectrometry (DMS-MS, also known as FAIMS). Focus was primarily directed to compositional isomers corresponding to epimers that differ by the axial or equatorial position of a single hydroxyl group. DMS resolving power was enhanced 14-fold primarily by increasing the fraction of helium in the ion carrier gas and lowering the flow rate. At relatively high disaccharide concentrations, DMS-MS of each disaccharide resulted in complex and unique multi-peak spectra with up to ten fully and partially resolved peaks for β-1,4-mannobiose (Man-1,4β-Man), which can be attributed to the DMS separation and subsequent dissociation of ionic non-covalently bound oligomers into monomer ions. Each DMS spectrum has at least one differentiating peak that is not in the other spectra, indicating that DMS can be used to fully or partially resolve composition, configuration and connectivity isomers. At relatively low disaccharide concentrations, mixtures of disaccharide epimers can also be readily separated by DMS. The integration of high-resolution, ambient pressure DMS with complementary reduced-pressure ion mobility and MS-based glycomics and glycoproteomics workflows may be useful for improving the characterization of glycans and glycosylated biomolecules.

Three-dimensional feature matching improves coverage for single-cell proteomics based on ion mobility filtering.

SUMMARYSingle-cell proteomics (scProteomics) promises to advance our understanding of cell functions within complex biological systems. However, a major challenge of current methods is their inability to identify and provide accurate quantitative information for low-abundance proteins. Herein, we describe an ion-mobility-enhanced mass spectrometry acquisition and peptide identification method, transferring identification based on FAIMS filtering (TIFF), to improve the sensitivity and accuracy of label-free scProteomics. TIFF extends the ion accumulation times for peptide ions by filtering out singly charged ions. The peptide identities are assigned by a three-dimensional MS1 feature matching approach (retention time, accurate mass, and FAIMS compensation voltage). The TIFF method enabled unbiased proteome analysis to a depth of >1,700 proteins in single HeLa cells, with >1,100 proteins consistently identified. As a demonstration, we applied the TIFF method to obtain temporal proteome profiles of >150 single murine macrophage cells during lipopolysaccharide stimulation and identified time-dependent proteome changes. A record of this paper’s transparent peer review process is included in the supplemental information.

Semi-metallic PC5 monolayer as a superior anode material for potassium ion batteries: A first principles study

Potassium ion batteries (PIBs) have been widely considered as appealing alternatives to lithium ion batteries (LIBs) because of their low-cost, good safety and high energy density; however, it is still challenging to search an outstanding anode material for PIBs owing to the big-size of potassium and sluggish reaction dynamics. Herein, using first principles computations, we identified an emerging phosphorous carbide (PC5) monolayer as a promising anode candidate of PIBs. The PC5 monolayer exhibits high electrical conductivity, which ensures rapid electronic transport during cycling. Moreover, the potassium diffusion barrier of PC5 is 0.18 eV, implying a high ionic mobility. On the whole intercalation process, the PC5 monolayer has strong affinity toward potassium and small volume expansion (0.57%), which could avoid the metallic dendrite formation and improve the cycle life. Remarkably, the specific capacity of PC5 is as high as 835.18 mA h/g, superior to many reported 2D materials. All the encouraging results reveal that PC5 is a high-performance anode of PIBs.

Electrochemical Properties of Trimethylammonium Tetrafluoroborate in Electrochemical Double-Layer Capacitors

Trimethylammonium tetrafluoroborate (TriMA BF4), consisting of the smallest trialkylammonium ion, was investigated for use in electrochemical double-layer capacitors. Despite the presence of a proton in TriMA+, cycle life tests in acetonitrile (AN) and -butyrolactone (GBL) showed a good capacity retention with a 1.8 V cut-off voltage. The rate of electrolysis of TriMA BF4 in GBL was lower than that in AN because of the lower conductivity in GBL. As a consequence, the cells based on GBL achieved a higher capacitance and longer life than those with AN. TriMA BF4 had a higher conductivity and lower viscosity than the quaternary salt tetraethylammonium tetrafluoroborate in GBL, as well as higher ionic mobility, these factors resulted in a higher rate capability.

Mapping Protein Structural Evolution upon Unfolding.

In the past, many intensive attempts failed to capture or underestimated the copopulated intermediate conformers from the protein folding/unfolding reaction. We report a promising approach to kinetically trap, resolve, and quantify protein conformers that evolve during unfolding in solution. We conducted acid-induced unfolding of three model proteins (cytochrome c, myoglobin, and lysozyme), and the corresponding reaction aliquots upon decreasing the pH were electrosprayed for high field asymmetric waveform ion mobility spectrometry (FAIMS) measurements. The copopulated conformers were resolved, visualized, and quantified by a two-dimensional mapping of the FAIMS output. Contrary to expectations, all the above proteins appeared metamorphic (multiple-folded conformations) at the physiological pH, and cytochrome c exhibited an unusual "conformational shuttling" before forming the molten globule state. Thus, in contrast to many previous studies, a wide variety of thermodynamically stable intermediate conformers, including compact, molten globule, and partially unfolded forms, was trapped from solution, probing the unfolding mechanism in detail.

Ionic Control over Ferroelectricity in 2D Layered van der Waals Capacitors.

The van der Waals layered material CuInP2S6 features interesting functional behavior, including the existence of four uniaxial polarization states, polarization reversal against the electric field through Cu ion migration, a negative-capacitance regime, and reversible extraction of Cu ions. At the heart of these characteristics lies the high mobility of Cu ions, which also determines the spontaneous polarization. Therefore, Cu migration across the lattice results in unusual ferroelectric behavior. Here, we demonstrate how the interplay of polar and ionic properties provides a path to ionically controlled ferroelectric behavior, achieved by applying selected DC voltage pulses and subsequently probing ferroelectric switching during fast triangular voltage sweeps. Using current measurements and theoretical calculations, we observe that increasing DC pulse duration results in higher ionic currents, the buildup of an internal electric field that shifts polarization loops, and an increase in total switchable polarization by ∼50% due to the existence of a high polarization phase which is stabilized by the internal electric field. Apart from tuning ferroelectric behavior by selected square pulses, hysteretic polarization switching can even be entirely deactivated and reactivated, resulting in three-state systems where polarization switching is either inhibited or can be performed in two different directions.