Rearrangement Of Ions Research Articles

Oxygen Vacancies Altering the Trapping in the Proton Conduction Landscape of Doped Barium Zirconate

Acceptor-doped barium zirconate is one of the most promising proton conducting materials for stationary hydrogen fuel cells. Dopant-defect proton traps shape the proton conduction landscape. Inspired by findings that oxygen vacancies may decrease trapping near some dopant defects ( Chem. Mater. 2018, 30, 4919−4925), the effect of oxygen vacancies on the proton conduction landscape of barium zirconate is explored at 12.5% doping with aluminum, scandium, and yttrium dopant at the zirconium site. Density functional theory (DFT) with the PBE functional in the Vienna ab initio simulation package (VASP) was used to find the electronic energy for barium zirconate configurations. The conjugate-gradient minimization method is used to find the lowest energy structures and the climbing nudged elastic band (cNEB) method is used to find transition states. As the dopant (D) ion radius increases, the lattice size expands from 4.24 to 4.29 Å and increases DO6 octahedral tilting in barium zirconate. Inclusion of an oxygen vacancy broadens ZrOD and ZrOZr angle distributions. While there are three distinct minima for oxygen vacancy locations, relative energies of minima and transition states show that only the dopant nearest neighbor oxygen vacancy is significant for aluminum- and scandium-doped barium zirconate. In contrast, the yttrium-doped system shows 67% and 33% probabilities at 800 K for the dopant nearest and second nearest neighbor oxygen vacancies, respectively. The dopant nearest oxygen vacancy leaves the dopant polyhedral center charge exposed. The small size of the aluminum dopant allows oxygen ions to shift and partially screen the dopant charge. This coupled with strong hydrogen bonds increases proton trapping. For the larger scandium and yttrium ions, there is no significant oxygen ion rearrangement around the dopant with a nearest neighbor oxygen vacancy. Instead, the positive dopant charge exposed by the vacancy raises the energy of several dopant nearest neighbor proton sites decreasing trapping locally.

Unimolecular Fragmentation Properties of Thermometer Ions from Chemical Dynamics Simulations.

Thermometer ions are widely used to calibrate the internal energy of the ions produced by electrospray ionization in mass spectrometry. Typically, benzylpyridinium ions with different substituents are used. More recently, benzhydrylpyridinium ions were proposed for their lower bond dissociation energies. Direct dynamics simulations using M06-2X/6-31G(d), DFTB, and PM6-D3 are performed to characterize the activation energies of two representative systems: para-methylbenzylpyridinium ion (p-Me-BnPy+) and methyl,methylbenzhydrylpyridinium ion (Me,Me-BhPy+). Simulation results are used to calculate rate constants for the two systems. These rate constants and their uncertainties are used to find the Arrhenius activation energies and RRK fitted threshold energies which give reasonable agreement with calculated bond dissociation energies at the same level of theory. There is only one fragmentation mechanism observed for both systems, which involves C-N bond dissociation via a loose transition state, to generate either benzylium or benzhydrylium ion and a neutral pyridine molecule. For p-Me-BnPy+ using DFTB and PM6-D3 the formation of tropylium ion, from rearrangement of benzylium ion, was observed but only at higher excitation energies and for longer simulation times. These observations suggest that there is no competition between reaction pathways that could affect the reliability of internal energy calibrations. Finally, we suggest using DFTB with a modified-Arrhenius model in future studies.

Investigation of the Ionic Liquid Graphene Electric Double Layer in Supercapacitors Using Constant Potential Simulations

In this work, we investigate the effect of the cation structure on the structure and dynamics of the electrode–electrolyte interface using molecular dynamics simulations. A constant potential method is used to capture the behaviour of 1-ethyl-3-methylimidazolium bis (trifluoromethane)sulfonimide ([Cmim][NTf]) and butyltrimethylammonium bis(trifluoromethane) sulfonimide ([N][NTf]) ionic liquids at varying potential differences applied across the supercapacitor. We find that the details of the structure in the electric double layer and the dynamics differ significantly, yet the charge profile and capacitance do not vary greatly. For the systems considered, charging results in the rearrangement and reorientation of ions within ∼1 nm of the electrode rather than the diffusion of ions to/from the bulk region. This occurs on timescales of (10 ns) for the ionic liquids considered, and depends on the viscosity of the fluid.

Mass Spectrometry-Based Discovery of New Chemical Scaffold Rearrangement Ions: Aza-biphenylene as a Novel Potent Biradical Agent in Cancer Chemotherapy.

Discovery of a new drug is time-consuming, laborious, and expensive. Herein, a novel integrative strategy for discovering potential new lead compounds has been developed, which was based on the characteristics of mass spectrometry (MS). MS was used to predict the potential forced degradation products (DPs) and metabolites of drugs by electrospray ionization and collision-induced dissociation (CID). Special rearrangement ions representing unique predicted DPs and metabolites were identified. The consistency between the predicted and the measured results was proven by in vitro metabolism and forced degradation of a commercial drug, respectively. From this, new chemical scaffold rearrangement ions named (aza)-biphenylenes, as potent anticancer agents, were discovered. As a representative aza-biphenylene analogue, 2-azabiphenylene was proven in vitro to induce apoptosis and inhibit the growth of various human cancer cells in a dose-dependent manner. Surprisingly, 2-azabiphenylene exhibited the best comparable bioactivity with the positive control sorafenib, but showed significantly lower in vitro cytotoxicity than sorafenib (at least a 5-fold decrease in cytotoxicity) because it could be targeted to the tumor microenvironment at low pH. A biradical mechanism accompanied by a mitochondrion-dependent oxidative stress mechanism was proposed to explore its anticancer mechanism. The highly reactive intermediate aza-biphenylenediyl worked as an active pharmaceutical ingredient and induced apoptosis of cancer cells. This provided the basis for the potential applications of CID-induced special rearrangement ions in developing new lead compounds.

Ionic Liquids as Extractants for Nanoplastics.

Plastic waste in the ocean and on land in the form of nanoplastics is endangering food and drinking water supplies, raising the need for new strategies for the removal of plastic nanoparticles from complex media. In the present contribution we suggest considering ionic liquids as extractants, since they show several advantageous properties that may facilitate the design of efficient separation processes. Through varying the anion and the side chain at the cation, the interactions between the extractant and the polymer can be strengthened and tuned, and thereby the disintegration of the particle into separate polymer chains can be controlled. Oxidized moieties can also be efficiently solvated, given the amphiphilic nature of the considered ionic liquids, allowing also realistic particles to be extracted into these solvents. The phase transfer was found to be thermodynamically and kinetically possible, which is supported by the complicated structure of the ionic liquid‐water interface through the rearrangement of the interfacial ions, and the formation of a micelle around the plastic already at the edge of the aqueous phase.

Rearrangements of diferrocenylcyclopropenium ions in the reactions with bis-1,4-O,S-nucleophiles

Reactions of 3-R-1,2-diferrocenylcyclopropenium ions (R is 4-morpholino or SMe) with 2-mercaptophenol or 2-mercaptoethanol proceed via a ring opening and result in three types of products, namely, diferrocenyl-substituted 1,3-oxathiolanes, 1,4-oxathiepines and alkyl prop-2-enethioates.

Hydrodynamic dispersion by electroosmotic flow in soft microchannels: Consideration of different properties for electrolyte and polyelectrolyte layer

We theoretically study the hydrodynamic dispersion by fully developed electroosmotic flow in soft slit microchannels of dense polyelectrolyte layer (PEL). When the PEL is dense, the smallness of its permittivity with respect to the fluid leads to the rearrangement of ions, a phenomenon known as ion partitioning. Moreover, the fluid viscosity gets much higher within the PEL while the opposite happens to molecular diffusivity. Adopting the Debye-Hückel linearization, we obtain analytical solutions for electric potential and velocity distributions by considering different values of permittivity and viscosity inside and outside the PEL. The velocity profile is then used to derive expressions for long-term analyte concentration and dispersion coefficient. Full numerical simulations are also performed to track the broadening of an analyte band from the time of injection. The results indicate that ion partitioning gives rise to the amplification of fluid velocity and, hence, the hydrodynamic dispersion, whereas the opposite is true for the increase in the dynamic viscosity within the PEL. Moreover, even though the reduction of the molecular diffusivity inside the PEL leads to the increase of the dispersion coefficient, its influence is much weaker than those of the ion partitioning and the viscosity variations.

Remaining Li-Content Dependent Structural Evolution during High Temperature Re-Heat Treatment of Quantitatively Delithiated Li-Rich Cathode Materials with Surface Defect-Spinel Phase.

Pre-extracting Li+ from Li-rich layered oxides by chemical method is considered to be a targeted strategy for improving this class of cathode material. Understanding the structural evolution of the delithiated material is very important because this is directly related to the preparation of electrochemical performance enhanced Li-rich material. Herein, we perform a high temperature reheat treatment on the quantitatively delithiated Li-rich materials with different amounts of surface defect-spinel phase and carefully investigate the structural evolution of these delithiated materials. It is found that the high temperature reheat treatment could cause the decomposition of the unstable surface defect-spinel structure, followed by the rearrangement of transition metal ions to form the thermodynamically stable phases, More importantly, we find that this process has high correlation with the remaining Li-content in the delithiated material. When the amount of extracted Li+ is relatively small (corresponding to the higher remaining Li-content), the surface defect-spinel phase could be dominantly decomposed into the LiMO2 (M = Ni, Co, and Mn) layered phase along with the significant improvement of electrochemical performance, and continuing to decrease remaining Li-content could lead to the emergence of M3O4-type spinel impurity embedding in the final product. However, when the extracted Li+ further achieves a certain amount, after the high temperature heat-treatment the Mn-rich Li2MnO3 phase (C2/m) could be separated from Ni-rich phases (including R3m, Fd3m, and Fm3m), thus resulting in a sharp deterioration of initial capacity and voltage. These findings suggest that reheating the delithiated Li-rich material to high temperature may be a simple and effective way to improve the predelithiation modification method, but first the amount of extracted Li+ should be carefully optimized during the delithiation process.

Precipitation of silver nanoparticle within silicate glassy matrix via Nd:YAG laser for biomedical applications

Nanosecond Nd:YAG laser technique as a unique method was adopted for the precipitating of silver nanoparticles within a bulk glass material. Soda-lime silica glass of nominal composition 75SiO 2 .15Na 2 O.10CaO (mol %) and other samples containing 0.25, 0.50, 1.00 g per batch overweight silver nitrate were successfully synthesized via traditional melt quenching route. Synthesized samples were subjected to Nd:YAG laser irradiation. Upon laser irradiation, a noticeable shift of color was detected inside the regions of the silicate glasses which was due to the development of silver nanoparticles. XRD patterns indicate the decrease in the characteristics of two halos at about 27° and 44° with increasing the precipitated AgNPs content inside the silicate glassy matrix. FT-IR spectra show minor changes in the fingerprint region attributed to the rearrangement of silver ion within the glassy matrix. The optical absorption spectra confirm the formation of red shift in the band position at 420 nm which have been obtained with increasing the content of silver nanoparticle precipitated in the silicate glasses. The morphological investigation according to HR-TEM and FE-SEM micrographs confirms silver nanoparticles precipitated in the silicate glasses after laser irradiation. Studied antibacterial activity against pathogenic grams indicates great enhancement with increasing precipitated silver nanoparticles content within the silicate glasses and suggests their suitability for different biomedical applications. • AgNPs have been precipitated in silicate glasses via Nd:YAG Laser. • XRD and FT-IR results confirmed the formation of AgNPs participate in the silicate glass samples. • UV–Visible spectra confirm the formation of AgNPs through Surface Plasmon. • The morphological investigation confirm the precipitation of silver within the samples after laser irradiation. • In vitro antimicrobial, increasing of AgNPs content result in the increase of the diameter zone and activity index.

Self-Discharge Characteristics of Vapor Deposited Polymer Electrodes in an All-Textile Supercapacitor

Despite the many efforts put toward developing flexible supercapacitors for wearable technology, few studies have focused on self-discharge, the spontaneous voltage decay of devices stored in their charged state. In this work, we study and seek to improve the self-discharge behavior of a high-loading, all-textile charge storage device comprised of two conducting polymer-coated prewoven fabrics as the active electrodes. The enabling pseudocapacitive polymer coating on these fabric electrodes is a persistently p-doped conducting polymer, poly(3,4-ethylenedioxythiophene)-chloride (PEDOT-Cl), that we vapor deposit onto untreated commercial textiles using a custom-built hot wall reactor, following a previously reported process.We find that a significant portion of apparent self-discharge in this vapor-deposited pseudocapacitive soft material is due to charge redistribution, a physical process involving the rearrangement of ions within the electrode material. Primarily observed for highly porous carbon materials, charge redistribution arises when, during charging, ions accumulate at high-low resistance interfaces (i.e., at pore mouths) and subsequently redistribute throughout the material. A higher density of charge yields a higher electrode surface potential that diminishes as the charges diffuse through higher resistance regions. A hold step used during charging pre-conditions our polymer electrodes, reducing self-discharge losses by uniformly diffusing charges throughout the film. Among the scarce studies on self-discharge of conducting polymers, none to our knowledge have identified charge redistribution as a mechanism for this behavior.The magnitude of the observed charge redistribution effects was modeled using a circuit model with two RC branches, representing the slowest and fastest responding regions. The resistance of the slow branch was found to be about three orders of magnitude higher than that of the fast branch. The ratio of these resistances was quite similar to those reported for porous carbon electrodes. However, since the polymer films contained essentially no micropores (BET surface area = 6.7 m2/g), an alternative explanation was needed for the observed charge redistribution effects.A distinguishing feature between electrochemical double-layer capacitors (EDLC’s) and pseudocapacitors is that charge storage is a surface phenomenon in the former and a bulk phenomenon in the latter. We propose, in analogy, that the charge redistribution we observed in PEDOT-Cl electrodes arose not due to pore characteristics, but to varying crystallinity (and the presence of crystal domain walls, in particular) across the bulk polymer film. During a redox cycle, chloride ions must travel through these crystal interstices with dimensions comparable to their hydrated diameter. We anticipate dramatically higher resistance to transport in these crystalline regions than in the free-volume-rich disordered regions of the polymer. Such morphology-dependent ion effects have been observed for other conjugated polymers. At short charge times, we expect that ions build up at the interface of ordered and disordered regions before uniformly redistributing throughout. Judicious control of polymer morphology, namely the degree of crystallinity and orientation of crystallites, may be used to facilitate ion transport and minimize the ion accumulation associated with charge redistribution. Indeed, the variation of crystallite orientation in vapor-deposited PEDOT-Cl films has previously been shown to influence resulting electrochemical properties via ion transport effects.The remainder of self-discharge losses are found to be associated with a diffusion-limited process, likely involving a low-concentration impurity. Iron oxidant residues (a reagent used in the polymer deposition) were ruled out as a potential contribution, while oxygen reduction remains a likely possibility.As a matter of practical importance for integrating flexible energy storage devices into functional systems, self-discharge of conjugated polymer-based electrodes was investigated, and crystallinity-dependent ion dynamics were proposed to be responsible for a portion of the observed voltage decay. Future work directed at charge redistribution in polymers might focus on control of morphology to provide amorphous networks for ions to more efficiently percolate through. Figure 1

Observation of Ion Electrosorption in Metal–Organic Framework Micropores with In Operando Small‐Angle Neutron Scattering

AbstractA molecular‐level understanding of transport and adsorption mechanisms of electrolyte ions in nanoporous electrodes under applied potentials is essential to control the performance of double‐layer capacitors. Here, in operando small‐angle neutron scattering (SANS) is used to directly detect ion movements into the nanopores of a conductive metal–organic framework (MOF) electrode under operating conditions. Neutron‐scattering data reveals that most of the void space within the MOF is accessible to the solvent. Upon the addition of the electrolyte sodium triflate (NaOTf), the ions are adsorbed on the outer surface of the protrusions to form a 30 Å layer instead of entering the ionophobic pores in the absence of an applied charging potential. The changes in scattering intensity when potentials are applied suggests the ion rearrangement in the micropores following different mechanisms depending on the electrode polarization. These observations shed insights on ion electrosorption in electrode materials.

Observation of Ion Electrosorption in Metal-Organic Framework Micropores with In Operando Small-Angle Neutron Scattering.

A molecular-level understanding of transport and adsorption mechanisms of electrolyte ions in nanoporous electrodes under applied potentials is essential to control the performance of double-layer capacitors. Here, in operando small-angle neutron scattering (SANS) is used to directly detect ion movements into the nanopores of a conductive metal-organic framework (MOF) electrode under operating conditions. Neutron-scattering data reveals that most of the void space within the MOF is accessible to the solvent. Upon the addition of the electrolyte sodium triflate (NaOTf), the ions are adsorbed on the outer surface of the protrusions to form a 30 Å layer instead of entering the ionophobic pores in the absence of an applied charging potential. The changes in scattering intensity when potentials are applied suggests the ion rearrangement in the micropores following different mechanisms depending on the electrode polarization. These observations shed insights on ion electrosorption in electrode materials.

Determining phase transitions of layered oxides via electrochemical and crystallographic analysis

ABSTRACT The chemical diffusion coefficient in LiNi1/3Mn1/3Co1/3O2 was determined via the galvanostatic intermittent titration technique in the voltage range 3 to 4.2 V. Calculated diffusion coefficients in these layered oxide cathodes during charging and discharging reach a minimum at the open-circuit voltage of 3.8 V and 3.7 V vs. Li/Li+, respectively. The observed minima of the chemical diffusion coefficients indicate a phase transition in this voltage range. The unit cell parameters of LiNi1/3Mn1/3Co1/3O2 cathodes were determined at different lithiation states using ex situ crystallographic analysis. It was shown that the unit cell parameter variation correlates well with the observed values for chemical diffusion in NMC cathodes; with a notable change in absolute values in the same voltage range. We relate the observed variation in unit cell parameters to the nickel conversion into the trivalent state, which is Jahn-Teller active, and to the re-arrangement of lithium ions and vacancies.

Generation of 1-azabicyclo[3.2.1]octane and 5-azatricyclo[3.2.1.02,7]octane systems by carbenium ion rearrangements during production of the antihistamine drug Quifenadine

Dehydration of ethyl 3-hydroxyquinuclidine-3-carboxylate is one of the key steps during production of the antihistamine drug Quifenadine (Phencarol). The side products of this process were isolated and their structures proved using NMR spectroscopy. Carbenium ion rearrangements of quinuclidine-3-carboxylate gave rise to 1-azabicyclo[3.2.1]octane and 5-azatricyclo[3.2.1.02,7]octane systems, which serve as impurity standards for the manufacturing process of Quifenadine and are also interesting building blocks for medicinal chemistry.

Towards Real-Time Ion-Specific Structural Sensitivity in Nanoporous Carbon Electrodes Using In Situ Anomalous Small-Angle X-ray Scattering.

Current in situ techniques to study ion charge storage and electrical double-layer formation in nanoporous electrodes are either chemically sensitive to element-specific concentration changes or structurally sensitive to rearrangements of ions and solvent molecules; but rarely can they cover both. Here we introduce in situ anomalous small-angle X-ray scattering (ASAXS) as a unique method to extract both real-time structural and ion-specific chemical information from one single experiment. Using a 1 M RbBr aqueous electrolyte and a hierarchical micro- and mesoporous carbon electrode, we identify different charging mechanisms for positive and negative applied potentials. We are able not only to track the global concentration change of each ion species individually, but also to observe their individual local rearrangement within the pore space.

Dynamical Magnetic Field Accompanying the Motion of Ferroelectric Domain Walls.

The recently proposed dynamical multiferroic effect describes the generation of magnetization from temporally varying electric polarization. Here, we show that the effect can lead to a magnetic field at moving ferroelectric domain walls, where the rearrangement of ions corresponds to a rotation of ferroelectric polarization in time. We develop an expression for the dynamical magnetic field, and calculate the relevant parameters for the example of 90° and 180° domain walls, as well as for polar skyrmions, in BaTiO_{3}, using a combination of density functional theory and phenomenological modeling. We find that the magnetic field reaches the order of several μT at the center of the wall, and we propose two experiments to measure the effect with nitrogen-vacancy center magnetometry.

Spontaneous Interface Ion Exchange: Passivating Surface Defects of Perovskite Solar Cells with Enhanced Photovoltage

AbstractInterface engineering is of great concern in photovoltaic devices. For the solution‐processed perovskite solar cells, the modification of the bottom surface of the perovskite layer is a challenge due to solvent incompatibility. Herein, a Cl‐containing tin‐based electron transport layer; SnOx‐Cl, is designed to realize an in situ, spontaneous ion‐exchange reaction at the interface of SnOx‐Cl/MAPbI3. The interfacial ion rearrangement not only effectively passivates the physical contact defects, but, at the same time, the diffusion of Cl ions in the perovskite film also causes longitudinal grain growth and further reduces the grain boundary density. As a result, an efficiency of 20.32% is achieved with an extremely high open‐circuit voltage of 1.19 V. This versatile design of the underlying carrier transport layer provides a new way to improve the performance of perovskite solar cells and other optoelectronic devices.

Water-Induced Breaking of the Coulombic Ordering in a Room-Temperature Ionic Liquid Metal Complex.

Control of ion arrangements in ionic liquids represents a major challenge owing to the presence of the predominant coulombic interactions between cationic and anionic ion species that forms the coulombic ordering. Here, water-induced ion rearrangement in a room-temperature ionic liquid (RT-IL) metal complex, (1-ethyl-3-methylimidazolium)2 [MnN(CN)4 ], is demonstrated through coordinative interactions between anions. Solidification occurred, which was associated with the formation of a "separated" structure consisting of cation columns and anionic cyanide-bridged one-dimensional coordination polymers. The energy diagram is in accord with the resultant RT-IL incorporating mononuclear [MnN(CN)4 ]2- molecules being a kinetic phase stabilized by inter-ion repulsions of the anionic divalent metal complex moieties. Water acts to decrease the coulombic interactions, including repulsion, giving rise to breaking of the coulombic ordering arising from coordination bond formation in the IL phase.

Schmidt Reaction of ω-Azido Valeryl Chlorides Followed by Intermolecular Trapping of the Rearrangement Ions: Synthesis of Assoanine and Related Pyrrolophenanthridine Alkaloids.

The Schmidt reaction of ω-azido valeryl chlorides in the presence of an additional nucleophile was explored. The arenes, alcohols, and amines were demonstrated as the intermolecular trapping reagents for isocyanate ion and N-acyliminium ion from the Schmidt rearrangement, affording the corresponding products with moderate to excellent yields. Two 2-oxoindoles from the reaction were successfully converted into four natural alkaloids, namely, assoanine, anhydrolycorine, oxoassoanine, and anhydrolycorinone.

Unveiling New Isomers and Rearrangement Routes on the C7H8+ Potential Energy Surface

The unimolecular reactions of C7H8+ radical cations are among those most studied by mass spectrometry, especially the rearrangement of toluene and cycloheptatriene molecular ions, which are directly connected to the formation of benzylium and tropylium cations. This study reveals important new isomers and isomerization pathways on the C7H8+ potential energy surface, through the application of gas-phase electronic photodissociation spectroscopy in conjunction with ab initio calculations. Presented are the first gas-phase vibrationally resolved electronic spectra of the o-isotoluene, norcaradiene, bicyclo[3.2.0]hepta-2,6-diene radical cations, and ring-opened products from cyclic C7H8+ species. The isomerization route from the norbornadiene radical cation to the toluene radical cation, which competes with isomerization to the bicyclo[2.2.1]hepta-2-ene-5-yl-7-ylium radical cation, is identified. Further, this work expands understanding of the C7H8+ potential energy surface by connecting spiro[2.4]hepta-4,6-diene and acyclic 1,2,4,6-heptatetraene radical cations, and confirms the important role of the o-isotoluene radical cation in the interconversion pathways of C7H8+ species.