Anion Size Research Articles

Precise Post‐Synthetic Modification of Heterometal‐Organic Capsules for Selectively Encapsulating Tetrahedral Anions

AbstractPost‐synthetic modification plays a crucial role in precisely adjusting the structure and functions of advanced materials. Herein, we report the self‐assembly of a tubular heterometallic Pd3Cu6L16 capsule that incorporates Pd(II) and CuL1 metalloligands. This capsule undergoes further modification with two tridentate anionic ligands (L2) to afford a bicapped Pd3Cu6L16L22 capsule with an Edshammer polyhedral structure. By employing transition metal ions, acid, and oxidation agents, the bicapped capsule can be converted into an uncapped one. This uncapped form can then revert back to the bicapped structure on the addition of Br− ions and a base. Interestingly, introducing Ag+ ions leads to the removal of one L2 ligand from the bicapped capsule, yielding a mono‐capped Pd3Cu6L16L2 structure. Furthermore, the size of the anions critically influences the precise control over the post‐synthetic modifications of the capsules. It was demonstrated that these capsules selectively encapsulate tetrahedral anions, offering a novel approach for the design of intelligent molecular delivery systems.

Precise Post-Synthetic Modification of Heterometal-Organic Capsules for Selectively Encapsulating Tetrahedral Anions.

Post-synthetic modification plays a crucial role in precisely adjusting the structure and functions of advanced materials. Herein, we report the self-assembly of a tubular heterometallic Pd3Cu6L16 capsule that incorporates Pd(II) and CuL1 metalloligands. This capsule undergoes further modification with two tridentate anionic ligands (L2) to afford a bicapped Pd3Cu6L16L22 capsule with an Edshammer polyhedral structure. By employing transition metal ions, acid, and oxidation agents, the bicapped capsule can be converted into an uncapped one. This uncapped form can then revert back to the bicapped structure on the addition of Br- ions and a base. Interestingly, introducing Ag+ ions leads to the removal of one L2 ligand from the bicapped capsule, yielding a mono-capped Pd3Cu6L16L2 structure. Furthermore, the size of the anions critically influences the precise control over the post-synthetic modifications of the capsules. It was demonstrated that these capsules selectively encapsulate tetrahedral anions, offering a novel approach for the design of intelligent molecular delivery systems.

A simple approach for improving the photovoltaic efficiency of organic solar cells through polymer modification via anion exchange as the interlayer

A simple anion exchange was used to synthesize polyelectrolytes based on naphthalene diimide (NDI), which were then applied as a cathode interlayer in organic solar cells (OSCs). These polyelectrolytes can be dissolved in alcohols and produce a beneficial interface dipole due to the ionic functionality in the side chain. The PCE of the OSC utilizing PFN-NDI-OH as the cathode interlayer showed an enhancement compared to the pristine ZnO-based device, increasing from 8.79 % to 8.91 %. This improvement can be attributed to the polar nature of PFN-NDI-OH, which facilitates a strong adhesion between the inorganic metal oxide and the organic active layer. The device with PFN-NDI-OTs exhibited an enhanced PCE of up to 9.41 % due to the size of the counteranion was found to be related to the PCE, as converting the hydroxide to a tosylate anion increased the PCE, with the larger size of the tosylate anion playing a role in enhancing the Jsc. These results indicate that these polyelectrolytes are a promising candidate for use as a cathode interlayer in OSCs, with the additional advantage of being able to improve interfacial properties through a simple anion exchange process without time-consuming purification steps.

Ion effects on minimally hydrated polymers: hydrogen bond populations and dynamics.

Compared to bulk water, the effect of ions in confined environments or heterogeneous aqueous solutions is less understood. In this study, we characterize the influence of ions on hydrogen bond populations and dynamics within minimally hydrated polyethylene glycol diacrylate (PEGDA) solutions using Fourier-transform infrared (FTIR) and two-dimensional infrared (2D IR) spectroscopies. We demonstrate that hydrogen bond populations and lifetimes are directly related to ion size and hydration levels within the polymer matrix. Specifically, larger monovalent cation sizes (Li+, Na+, K+) as well as anion sizes (F-, Cl-, Br-) increase hydrogen bond populations and accelerate hydrogen bond dynamics, with anions having more pronounced effects compared to cations. These effects can be attributed to the complex interplay between ion hydration shells and the polymer matrix, where larger ions with diffuse charge distributions are less efficiently solvated, leading to a more pronounced disruption of the local hydrogen bonding network. Additionally, increased overall water content results in a significant slowdown of dynamics. Increased water content enhances the hydrogen bonding network, yet simultaneously provides greater ionic mobility, resulting in a delicate balance between stabilization and dynamic restructuring of hydrogen bonds. These results contribute to the understanding of ion-specific effects in complex partially-hydrated polymer systems, highlighting the complex interplay between ion concentration, water structuring, and polymer hydration state. The study provides a framework for designing polymer membrane compositions with ion-specific properties.

Counter-anion size engineering in polyfluorene-based cathode interlayers to enhance thickness independence

We synthesized a novel cathode interlayer material by replacing a Br anion with a TFSI anion. The increased anion size hindered the intermolecular interaction, allowing for the suppression of self-aggregation even on thick films.

Interionic bonding in aqueous phosphonium ionic liquid solutions exhibiting LCST behavior with high phase separation temperatures

Phosphonium-derived ionic liquids have emerged as a powerful class of thermoresponsive materials with sought after Lower Critical Solution Temperature (LCST) phase separation with applications across a broad range of fields. Herein, we report the spectroscopic examination of phosphonium salts bearing the general structure [X][P444n] wherein systematic structural variations were designed to gain a fundamental understanding behind the impact of alkyl chain length, anion size, and effective nuclear charge on their temperature-dependent phase separation behavior. Using variable temperature 1H, 31P, and 19F NMR, the bonding changes which drive LCST phase separation for the assembled thermoresponsive ILs were elucidated. For the first time, spectroscopic evidence revealed a delicate balance between the interdependence of alkyl chain length and anion size on phase separation that formed the basis of new LCST design principles.

Polyvalent anion-induced J-aggregation and its use in ratiometric fluorescence tracking of hypotonic in Arabidopsis

J-aggregate dyes have been widely used in biomedicine, chemical engineering, etc., due to their structure and photophysical properties. J-aggregation theory describes the nearest-neighbor molecules' transition dipole moments in a sliding stacking arrangement. However, we found that the intervention of polyvalent anions can induce the J-aggregation of dyes via the intermolecular van der Waals and electrostatic interactions, which is an essential way once overlooked. Experimental results and theoretical calculations revealed that the more negatively charged or large size of anions within a specific range, the more efficiently the dye will form J-aggregates. As an application, the content of polyvalent anion salts in a salt-stressed Arabidopsis model was evaluated based on the ratiometric fluorescence emission resulting from the polyvalent anion-induced dye J-aggregation.

Photocatalyst TiO2 assisted preparation by phosphonium ionic liquids enhancing degradation rate of VOCs

A series of TiO2 modified by phosphonium ionic liquids (PILs) and additives containing heteroatoms were synthesized. Among them, P, B, F and P, P, F doped catalysts effectively inhibited the crystal growth of TiO2, decreased the pore size and increased the surface area. What's more, PILs-TiO2 exhibited superior characteristics to those mentioned above. The characterization by FTIR, XPS and EPR demonstrated the generation of chemical bands and the introduction of oxygen vacancies and hydroxyl radicals in the samples. The photocatalytic degradation performance was evaluated and compared under simulated visible light for gaseous toluene. Compared with TiO2, degradation rate increased from 10.28 % to 28.42 %, 41.70 % and 46.23 % for [P4443][Br], [P4443][PF6] and [P4443][BF4] modified TiO2, respectively. In addition, the best photocatalytic degradation rate for T-P/Br, T-P/P/F and T-P/B/F increased to 13.54 %, 42.92 % and 43.78 %, respectively. Synergistic effect of elements in PILs resulted in beneficial photocatalytic degradation, which varied depending on the combination of different elements. Both heteroatoms in PILs and structure of PILs have significant effects on photocatalytic performance. The simulation showed that the presence of compactness of hydrogen bond network formed by PILs was beneficial, which was affected by the number of hydrogen bonds and the anion size.

Perturbation of Na-ion distribution for enhancement of ionic conductivity to a practical level of over 1 mS·cm−1 in Na3ZnGaS4

Na-ion conducting solid-state electrolytes (SSEs) are increasingly garnering attention as potential alternatives to Li-ion conducting SSEs in all-solid-state batteries. In this study, we demonstrate that replacing a small fraction of S2− with I− in Na3ZnGaS4 perturbs Na ion distributions, leading to an increase in vacancy concentration and a decrease in Na-Na distance along the conduction channel. This dual effect of I-substitution results in a remarkable increase in the ionic conductivity (σion) of Na3-xZnGaS4-xIx, from ca. 10−3 mS·cm−1 in pristine Na3ZnGaS4 to 1.12 mS·cm−1 in Na2.9ZnGaS3.9I0.1. Importantly, this enhancement cannot be achieved through simple vacancy incorporation via aliovalent doping. The incorporation of less I− (x = 0.05) or more I− (x = 0.15 and 0.2) also leads to significant improvements in σion, highlighting the effectiveness of disturbing the Na site. Cl- or Br-doped Na3ZnGaS4 similarly enhances σion, but to a more limited extent, underscoring the pivotal role of dopant anion sizes in inducing Na disturbance. We provide evidence for the presence of iodides in a specific sulfur site (S3 site) and the consequential dispersion of Na ions to Na2 and Na3 sites through a combination of theoretical, crystallographic, and spectroscopic studies. Additionally, we demonstrate the electrochemical and moisture stability of Na2.9ZnGaS3.9I0.1. Finally, due to its electrochemical stability and high σion, we exemplify the practicality of Na2.9ZnGaS3.9I0.1 in all-solid-state batteries using Na2Sn ‖ TiS2 full cells.

Molecular dynamic study on the transport properties of ionic liquids in ZTC porous carbon materials

The adsorption and diffusion behavior of ions within electrodes have a significant impact on the energy density and charging/discharging speed of supercapacitors. Zeolite-Templated Carbon (ZTC) material, a type of porous carbon material characterized by well-defined pore shape and spatial structure, is recognized as a promising electrode material owing to its numerous advantages. This study employs molecular dynamics simulations to investigate the diffusion and adsorption profiles of ionic liquids [EMI][BF4] in different types of ZTC materials as electrodes. Additionally, the effect of ion size, pore dimension, pore shape, and the properties of the adsorbed ions are discussed. The degree of confinement (DOC) and ion diffusivity are thoroughly analyzed to elucidate the transport behavior of ions within the ZTC pores. The results demonstrate that the diffusion coefficient and degree of confinement of ionic liquids predominantly depend on the anion size and the pore size of the porous carbon. Surprisingly, in certain cases, larger anions exhibit enhanced diffusion ability and adsorption effect. These findings unravel the underlying transport mechanism of ions in ZTC materials and provide valuable theoretical insights for the application of ZTC materials as electrodes in the field of supercapacitors.

Performance of ethanolamine-based ionic liquids as novel green electrolytes for the electrochemical energy storage applications

Supercapacitors are promising technologies for extremely effective energy storage and power management, which is a critical and major area of worldwide technological advancement. Ionic liquids (ILs) are an environmentally benign promising emerging class of versatile solvent systems. In this paper, for the first time, a new approach to the application of monoethanolamine-based ILs with anions formate, acetate, and propionate ([HEA]F, [HEA]A, and [HEA]P) as eco-friendly, affordable, and easy synthesis electrolytes are proposed for activated carbon (AC)-based supercapacitors. The ionic conductivity and the electrochemical stable potential window (ESPW) of ionic liquids were assessed. The electrochemical performance of synthesized ILs as an electrolyte in AC-based supercapacitors was compared. Electrochemical properties were performed by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), linear sweep voltammetry (LSV), and galvanostatic charge-discharge (GCD) methods to evaluate the electrolytic performance of ionic liquids in supercapacitors. The charge transfer resistance (Rct) and solution resistance (Rs) decreased with decreasing anion size of ILs. At a scan rate of 10 mVs−1, the prepared supercapacitors using [HEA]F, [HEA]A, and [HEA]P ionic liquids deliver specific capacitance of 114, 95, and 73 F g−1, respectively. The maximum power density 2941 W kg−1 and maximum energy density 70 Wh kg−1 were obtained for the prepared supercapacitor using [HEA]F ionic liquid. The supercapacitors prepared with [HEA]F, [HEA]A and [HEA]P electrolytes show capacitance retention of 96%, 91% and 87% after 5000 charge-discharge cycles, respectively.

Effect of anion size and salt concentration on ion transport in PEO-based solid polymer electrolytes at high temperatures

Effect of anion size and salt concentration on ion transport in PEO-based solid polymer electrolytes at high temperatures

Evolution of the resonances of small water cluster anions (H2O) n ⩽19 − in helium droplets upon attachment of electrons

Using a high-resolution electron monochromator, we studied the formation of (H2O) n ⩽19 − cluster ions upon collisions of free low-energy electrons with water clusters embedded in helium droplets. The anion efficiency curves as a function of the initial electron energy were measured for the cluster sizes n = 2–8, 10, 13, 16, and 19. The present experimental results show that the shape of the resonance yields is dependent on the size of the water cluster anion. The results are discussed in terms of the different electron states available for the excess electron from a linear cluster structure to three-dimensional cluster structures as the number of water molecules within the cluster increases.

Prediction of PP2A Holoenzymes Guided By the Structural Characterization of Methylation Independent PP2A Assembly

Introduction: The dysregulation of phosphorylation-dependent signaling is a hallmark of leukemogenesis. Kinase inhibitors have revolutionized the outcomes of patients with chronic myeloid leukemia. An orthogonal, but less explored way to target phosphorylation pathways is to activate phosphatases, such as the ubiquitously expressed protein- phosphatase 2A (PP2A). PP2A is an essential serine/threonine phosphatase that regulates various cellular processes, including cell growth, division, and differentiation. Dysregulation of PP2A has been linked to leukemia. PP2A is a modular multi-subunit enzyme: One scaffold subunit (A) binds to a catalytic subunit (C) to form a core AC heterodimer, which together with one of many regulatory (B) subunits forms the active enzyme. The regulatory (B) subunits are classified into 4 distinct subfamilies without significant homology. The combinatorial assembly of these subunits generates a wide range of PP2A complexes, resulting in diverse substrate specificity and subcellular localization. The detailed mechanism of PP2A regulation remains elusive and reports about a governing role of methylation of the carboxy-terminal Leucin of PP2A C are conflicting. Understanding the underlying molecular regulation of PP2A activity is of significant interest for future therapeutic development for acute myeloid leukemia. Methods: Recombinant PP2A was expressed in insect cells, and purified by affinity purification, anion exchange chromatography and size exclusion chromatography (SEC). Extensive quality control, including liquid chromatography-mass spectrometry, SDS-PAGE gel and fast protein liquid chromatography was performed. The degree of methylation of PP2A C Leucine 309 was confirmed by mass spectrometry. We validated protein stability with differential scanning fluorimetry. Pull-down assays and size exclusion chromatography characterized complex formation. A calorimetric assay using p-nitrophenyl phosphate as a substrate functionally assessed PP2A in vitro. Structural information was obtained by X-ray crystallography and AlphaFold Multimer. Results: Using in vitro biochemistry, including pull down and size exclusion chromatography, we demonstrate that methylation of the carboxy terminus of the PP2A C subunit is dispensable for PP2A assembly in vitro. Absence of methylation of Leucine 309 was confirmed by mass-spectrometry. We show by SEC that instead PP2A complex formation is dependent on B subunit concentration. Carboxy-terminal methylation of the PP2A C subunit was also not required for functional activity in a calorimetric assay using p-nitrophenyl phosphate as a substrate. PP2A formed spontaneously in vitro and was enzymatically active independent of methylation of Leucine 309. To corroborate these findings, we determined the X-ray crystal structure of the PP2A:PPP2B56E:PPP2C complex to 2.7 Å resolution with the unmethylated Leucine 309. Interestingly our experimental structure superimposed with an AlphaFold Multimer model of the PP2A trimer. Building on this finding, we predicted the models of all 64 possible PP2A complexes providing a framework for further study and structural analysis of PP2A complexes and their activation. These studies provide key information for the structural design and development of novel drugs for hematologic malignancies by targeting of selected PP2A complexes and clarified the role of Leucine 309 methylation in PP2A activation. Conclusion: Methylation of the carboxy-terminal Leucine 309 of the PP2A C subunitis dispensable for PP2A activity in vitro. Integrative structural biology studies, combining biochemistry, X-ray crystallography and AlphaFold Multimer provide a comprehensive map of PP2A complexes. These studies have the potential to accelerate the drug discovery process and unlock PP2A activation as a new therapeutic modality for leukemia.

2D Germanane‐MXene Heterostructures for Cations Intercalation in Energy Storage Applications

AbstractHeterostructures offer an exceptional possibility of combining individual 2D materials into a new material having altered properties compared to the parent materials. Germanane (GeH) is a 2D material with many favorable properties for energy storage and catalysis, however, its performance is hindered by its low electrical conductivity. To address the low electrochemical performance of GeH, a heterostructure of GeH and Ti3C2Tx is fabricated. The Ti3C2TX is a layered material belonging to the family of MXenes. The resulting heterostructure (GeMXene) at a defined mass ratio of GeH and Ti3C2Tx shows superior capacitive performance that surpasses that of both pristine materials. The effect of the size of cations and anions for intercalation into GeMXene in different aqueous salt solutions is studied. GeMXene allows only cation intercalation, which is evidenced by the gravimetric electrochemical quartz crystal microbalance (EQCM) technique. The capacitive performance of the GeMXene is compared in neutral, acidic, and alkaline electrolytes to determine the best electrochemical performance. This unleashes the potential use of GeMXene heterostructure in different electrolytes for supercapacitors and batteries. This work will pave the way to explore the heterostructures of other 2D materials such as novel MXenes and functionalized germanane for highly energy‐storage efficient systems, and beyond.

Thermodynamic study of imidazolium halide ionic liquid–water binary systems using excess Gibbs free energy models

In this work, the excess Gibbs free energy models, i.e., non-random two-liquid (NRTL) model and electrolyte NRTL model, including the original one and those with new strategies (association or hydration), were used to describe the macroscopic properties and interpret the microstructure of ionic liquid (IL) - H2O binary systems, clarifying the role of IL association and ion hydration in model development. To provide systematic data for model development, the enthalpy of mixing of three imidazolium-based IL-H2O systems containing the same cation but different sizes of anions, i.e., Cl−, Br−, and I−, were measured. The models were developed and evaluated based on the newly measured data and the osmotic coefficient from the literature. The results reveal that the model reflecting the intrinsic mechanism of dissociation and hydration gives the best modeling results; and the ionic strength and the degree of IL dissociation as a function of water content can be predicted using the newly established model. The study clarifies the significance of IL association and anion hydration in model development and quantitatively demonstrates how water content influences the microstructure and real species in IL-H2O systems.

Anions and Cations Affect Amino Acid Dissociation Equilibria via Distinct Mechanisms.

Salts reduce the pKa of weak acids by a mechanism sensitive to ion identity and concentration via charge screening of the deprotonated state. In this study, we utilize constant pH molecular dynamics simulations to understand the molecular mechanism behind the salt-dependent dissociation of aspartic acid (Asp). We calculate the pKa of Asp in the presence of a monovalent salt and investigate Hofmeister ion effects by systematically varying the ionic radii. We observe that increasing the anion size leads to a monotonic decrease in Asp pKa. Conversely, the cation size affects the pKa nonmonotonically, interpretable in the context of the law of matching water affinity. The net effect of salt on Asp acidity is governed by an interplay of solvation and competing ion interactions. The proposed mechanism is rather general and can be applicable to several problems in Hofmeister ion chemistry, such as pH effects on protein stability and soft matter interfaces.

Sodium-ion electrolytes based on poly-ethylene oxide oligomers in dual-carbon cells: Anion size drives the charging behavior

Sodium-ion dual-carbon electrochemical cells are an environmentally friendly technology for energy storage purposes. In such systems, the migration of mutual ions in both electrodes is crucial for performance and determines the cell’s behavior. To investigate this effect, we have performed force-field molecular dynamics simulations of dual-carbon sodium-ion systems containing poly-ethylene oxide (PEO6) as the solvent and two different anions, bis(trifluoromethanesulfonyl)imide (TFSI−) and bis(fluorosulfonyl)imide (FSI−). We used a constant potential model that allows simulating the charging behavior of these cells at the potential differences, ΔΨ=1, 2, 3, and 5 volt (V). Our results showed that considering the neat solution, NaTFSIPEO6 exhibited the best transport properties. However, NaFSIPEO6 is a better choice of electrolyte to be employed in dual-carbon cells since it provides higher and faster charge accumulation. Structural analysis also confirmed that the system containing NaFSIPEO6 stored more ions inside their respective electrodes with Na+ cations having fewer molecules composing their first solvation shell. Overall, our findings suggest that the smaller molecular volume of the FSI− anion is the key factor to properly fill the positive electrode, and the NaFSIPEO6 combination is the best choice for electrolytes of dual-carbon cells.

Anion exchange strategies in radical doped hole transporting material for high-efficiency perovskite solar cells

Perovskite solar cells (PSCs) have received significant attention due to their superior photovoltaic conversion capability. To date, most efficient PSCs use p-doped organic semiconductors as hole-transporting layers (HTL). Many evidences show that the generally used p-doping system, i.e. lithium bis(trifluoromethane)sulfonimide and air exposure threaten the reproducibility and stability of PSCs. Recently, free radicals doped HTL have been used to fabricate efficient PSCs without using anying harmful dopants. Herein, we found that the low doping efficiency of radials is due to a weak Madelung potential. We developed a spontaneous anion exchange to stabilize the radical doped HTL via introducing an additional anion into the host-guest system. Conductivity and interfacial charge transfer are significantly enhanced by regulating the size of anions. We found that the conductivity and device performance is increased when the size of the anion increases. As a result, a champion efficiency of 20.7% under AM 1.5G 1-sun irradiation is achieved, which is comparable with the conventionally doped HTL. Moreover, the solar cells showed significantly enhanced stability against the humidity stress, which we attribute to the use of HTLs devoid of environmental sensitive additives.

Self-assembling Gn head ferritin nanoparticle vaccine provides full protection from lethal challenge of Dabie bandavirus in aged ferrets.

Dabie bandavirus (DBV) is an emerging tick-borne virus that causes severe fever with thrombocytopenia syndrome (SFTS) in infected patients. Human SFTS symptoms progress from fever, fatigue, and muscle pain to the depletion of white blood cells and platelets with fatality rates up to 30%. The recent spread of its vector tick to over 20 states in the United States increases the potential for outbreaks of the SFTS beyond the East Asia. Thus, the development of vaccine to control this rapidly emerging virus is a high priority. In this study, we applied self-assembling ferritin (FT) nanoparticle to enhance the immunogenicity of DBV Gn head domain (GnH) as a vaccine target. Mice immunized with the GnH-FT nanoparticle vaccine induced potent antibody responses and cellular immunity. Immunized aged ferrets were fully protected from the lethal challenge of DBV. Our study describes the GnH-FT nanoparticle vaccine candidate that provides protective immunity against the emerging DBV infection.