Ion Solvation Research Articles

Kinetics and Mechanism of Electrochemical Reactions Occurring during the Chromium Electrodeposition from Electrolytes Based on Cr(III) Compounds: A Literature Review

A literature review was conducted to examine the current understanding of the kinetics and mechanism of electrochemical reactions occurring during the electrodeposition of chromium coatings from electrolytes based on trivalent chromium compounds. The research in this scientific field is crucial, as it addresses the pressing need for an alternative to chromium plating processes that rely on solutions containing highly toxic and harmful hexavalent chromium compounds. Numerous literature data on the kinetics and mechanism of the stepwise reduction process of Cr(III) complex ions were analyzed. The influence of various additives and surfactants on the reaction kinetics of the stepwise reduction of trivalent chromium ions was considered. Special attention was given to the kinetics of the stepwise discharge of trivalent chromium ions in ionic liquids and deep eutectic solvents.

Synergistic co-embedding of metal ions and hydrogen protons for high stability double salt aqueous aluminum battery

As a favorable competitor of the next generation for large-scale energy storage components, aluminum batteries (ABs) have received attention from all walks of life. However, the air sensitivity and corrosiveness of non-aqueous electrolytes seriously hinder the further development of aluminum ion batteries (AIBs). ABs meet the needs of green development and become a key research object. An excellent performance is reflected in the energy storage system of Al/4 M Al(OTF)3+1M Ca(OTF)2(4Al+Ca)/AlxMnO2·nH2O. It has an excellent discharge platform of 1.5 V, and can still maintain a high specific capacity of 233 mAh/g after 100 cycles. The co-intercalation of metal ions and protons has been demonstrated by EELS and SSNMR. What is most interesting is that during discharging, Ca2+ has the dual function of balancing charge and supporting material. MnO undergoes in-situ electrochemical conversion during charging and combines with Al3+ to form AlxMnO2·nH2O. In addition, the elaboration of the ion diffusion and solvation strategies inside the double-salt electrolyte is also an important exploration for the further development of aqueous aluminum batteries (AABs).

Unravelling Ultrafast Li Ion Transport in Functionalized Metal-Organic Framework-Based Battery Electrolytes.

Nonaqueous fluidic transport and ion solvation properties under nanoscale confinement are poorly understood, especially in ion conduction for energy storage and conversion systems. Herein, metal-organic frameworks (MOFs) and aprotic electrolytes are studied as a robust platform for molecular-level insights into electrolyte behaviors in confined spaces. By employing computer simulations, along with spectroscopic and electrochemical measurements, we demonstrate several phenomena that deviate from the bulk, including modulated solvent molecular configurations, aggregated solvation structures, and tunable transport mechanisms from quasi-solid to quasi-liquid in functionalized MOFs. Technologically, taking advantage of confinement effects may prove useful for addressing stability concerns associated with volatile organic electrolytes while simultaneously endowing ultrafast transport of solvates, resulting in improved battery performance, even at extreme temperatures. The molecular-level insights presented here further our understanding of structure-property relationships of complex fluids at the nanoscale, information that can be exploited for the predictive design of more efficient electrochemical systems.

Observing ion diffusion and reciprocating hopping motion in water.

When an ionic crystal dissolves in solvent, the positive and negative ions associated with solvent molecules release from the crystal. However, the existing form, interaction, and dynamics of ions in real solution are poorly understood because of the substantial experimental challenge. We observed the diffusion and aggregation of polyoxometalate (POM) ions in water by using liquid phase transmission electron microscopy. Real-time observation reveals an unexpected local reciprocating hopping motion of the ions in water, which may be caused by the short-range polymerized bridge of water molecules. We find that ion oligomers, existing as highly active clusters, undergo frequent splitting, aggregation, and rearrangement in dilute solution. The formation and dissociation of ion oligomers indicate a weak counterion-mediated interaction. Furthermore, POM ions with tetrahedral geometry show directional interaction compared with spherical ions, which presents structure-dependent dynamics.

What do far-infrared spectra of solitary water in "water-in-solvent" systems reveal about water's solvation and dynamics?

Classical molecular dynamics simulations of water in ionic and dipolar solvents were used to interpret the far-infrared (FIR) rotation/libration spectra of "solitary water" in terms of water's rotational dynamics and interactions with solvents. Seven solvents represented by nonpolarizable all-atom force fields and a series of idealized variable-charge solvents were used to span the range of solvent polarities (hydrogen bonding) studied experimentally. Simulated spectra capture the solvent dependence observed, as well as the relationship between the frequencies of water libration (νL) and OH stretching bands (νOH). In more strongly interacting solvents, simulated νL are ∼20% higher than those of experiment. In all solvents, the simulated spectra are composites of rotational motions about the two axes perpendicular to water's dipole moment, and the different frequencies of these two motions are responsible for the breadth of the libration band and the bimodal shape observed in halide ionic liquids. Simulations overestimate the separation of these two components in most solvents. The character of water rotational motions changes markedly with solvent polarity, from quasi-free rotation in nonpolar and weakly polar solvents to highly constrained libration in strongly hydrogen bonding environments. The changeover to librational motions dominating the spectrum occurs between solvents such as benzene (νL ∼ 250cm-1) and acetonitrile (νL ∼ 400cm-1). For solvents in the latter category, the mean frequency of the experimental FIR band provides a direct measure of mean-squared torques and, therefore, force constants associated with interactions constraining water's librational motion.

A Review of Opportunities and Methods for Recovery of Rhodium from Spent Nuclear Fuel during Reprocessing

Rhodium is one of the scarcest, most valuable, and useful platinum group metals, a strategically important material relied on heavily by automotive and electronics industries. The limited finite natural sources of Rh and exponentially increasing demands on these supplies mean that new sources are being sought to stabilise supplies and prices. Spent nuclear fuel (SNF) contains a significant quantity of Rh, though methods to recover this are purely conceptual at this point, due to the differing chemistry between SNF reprocessing and the methods used to recycle natural Rh. During SNF reprocessing, Rh partitions between aqueous nitric acid streams, where its speciation is complex, and insoluble fission product waste streams. Various techniques have been investigated for Rh recovery during SNF reprocessing for over 50 years, including solvent extraction, ion exchange, precipitation, and electrochemical methods, with tuneable approaches such as impregnated composites and ionic liquids receiving the most attention recently, assisted by more the comprehensive understanding of Rh speciation in nitric acid developed recently. The quantitative recovery of Rh within the SNF reprocessing ecosystem has remained elusive thus far, and as such, this review discusses the recent developments within the field, and strategies that could be applied to maximise the recovery of Rh from SNF.

A Comparative Study on Recent Developments for Individual Rare Earth Elements Separation

Facilitating the demands of modern society, namely, smartphones, televisions, electric vehicles, and high-stability aircraft structures, requires low-cost and high-performance materials and a corresponding change in the approach needed to design them. Rare earth elements (REEs) play a significant role in achieving these objectives by adding small amounts of these elements to alloys, thereby enhancing material properties. Despite being more abundant than precious metals, the 17 REEs exhibit subtle variations in their chemical and physical characteristics. Thus, their separation is still crucial for industrial applications. There is a corresponding need to develop more effective and efficient separation methods. Adding to the separation challenge is the complexity of the sources of REEs and related materials. Thus, large-scale production of REE materials is difficult. Current REE processing techniques can be categorized into pre-treatment, beneficiation, separation, and refining. Researchers have developed various technologies encompassing chemical, physical, and biological methods, focusing on economic and environmental considerations. However, not all these approaches can be scaled up for mass production. This article focuses on feasible strategies such as precipitation and crystallization, oxidation and reduction, ion exchange, adsorption, solvent extraction, and membrane separation. Further research into these traditional and modern methods can potentially revolutionize the separation dynamics of REEs.

Fluorinated Solvent Molecule Tuning Enables Fast‐Charging and Low‐Temperature Lithium‐Ion Batteries

AbstractPopularly‐used fluorination can effectively weaken Li+‐solvent interaction to facilitate the desolvation process at low temperature; however, high fluorination degree sacrifices salt dissociation and ionic conductivity. Herein, functional fluorinations are well tuned with different amounts of F atoms to balance Li+‐solvent binding energy and ion movement, which reveals the fluorination effect on the solvation behavior and low‐temperature performance. Noteworthily, the moderately‐fluorinated ethyl difluoroacetate (EDFA) successfully favors a lower binding energy than less‐fluorinated ethyl fluoroacetateand superior salt dissociation more than highly‐fluorinated ethyl trifluoroacetate, realizing the trade‐off between weak affinity and sufficient ionic conductivity. The well‐formulated EDFA‐based electrolyte exhibits a unique solvation sheath and generates inorganic‐rich solid electrolyte interphase with low resistance for smooth Li+ diffusion, which enables graphite anodes with excellent fast‐charging capability (196 mAh g−1 at 6 C) and impressive low‐temperature performance with a reversible capacity of 279 mAh g−1 under −40 °C. Subsequently, the wide electrochemical potential window of EDFA‐based electrolyte endows the 1.2 Ah LiNi0.8Co0.1Mn0.1O2 (NCM811)||graphite pouch cells with a high reversible capacity retention of 58.3% at −30 °C and discharge capacity of 790 mAh at −40 °C. Such solvent molecules with a moderately‐fluorinated strategy promise advanced electrolyte design for lithium‐ion batteries operating under harsh conditions.

Self‐Healing and ‐Repair of Nanomechanical Damages in Lead Halide Perovskites

AbstractRecovery from damage in materials helps extend their useful lifetime and of devices that contain them. Given that the photodamages in HaP materials and based devices are shown to recover, the question arises if this also applies to mechanical damages, especially those that can occur at the nanometer scale, relevant also in view of efforts to develop flexible HaP‐based devices. Here, this question is addressed by poking HaP single crystal surfaces with an atomic force microscope (AFM) tip under both ultra‐high vacuum (UHV) and variably controlled ambient water vapor pressure conditions. Sequential in situ AFM scanning allowed real‐time imaging of the morphological changes at the damaged sites. Using methylammonium (MA) and cesium (Cs) variants for A‐site cations in lead bromide perovskites, the experiments show that nanomechanical damages on methylammonium lead bromide (MAPbBr3) crystals heal an order of magnitude faster than Cs‐based ones in UHV. However, surprisingly, under ≥40% RH conditions, cesium lead bromide (CsPbBr3) shows MAPbBr3‐like fast healing kinetics. Direct evidence for ion solvation on CsPbBr3 is presented, leading to the formation of a surface hydration layer. The results imply that moisture improves the ionic mobility of degradation components and leads to water‐assisted improved healing, i.e., repair of nanomechanical damages in the HaPs.

An X-ray and Neutron Scattering Study of Aqueous MgCl2 Solution in the Gigapascal Pressure Range

The structure of electrolyte solutions under pressure at a molecular level is a crucial issue in the fundamental science of understanding the nature of ion solvation and association and application fields, such as geological processes on the Earth, pressure-induced protein denaturation, and supercritical water technology. We report the structure of an aqueous 2 m (=mol kg−1) MgCl2 solution at pressures from 0.1 MPa to 4 GPa and temperatures from 300 to 500 K revealed by X-ray- and neutron-scattering measurements. The scattering data are analyzed by empirical potential structure refinement (EPSR) modeling to derive the pair distribution functions, coordination number distributions, angle distributions, and spatial density functions (3D structure) as a function of pressure and temperature. Mg2+ forms rigid solvation shells extended to the third shell; the first solvation shell of six-fold octahedral coordination with about six water molecules at 0 GPa transforms into about five water molecules and one Cl− due to the formation of the contact ion pairs in the GPa pressure range. The Cl− solvation shows a substantial pressure dependence; the coordination number of a water oxygen atom around Cl− increases from 8 at 0.1 MPa/300 K to 10 at 4 GPa/500 K. The solvent water transforms the tetrahedral network structure at 0.1 MPa/300 K to a densely packed structure in the GPa pressure range; the number of water oxygen atoms around a central water molecule gradually increases from 4.6 at 0.1 MPa/298 K to 8.4 at 4 GPa/500 K.

Cellulose dissolution in mixtures of ionic liquids and molecular solvents: The fruitful synergism of experiment and theory

We investigated the dependence of dissolution of microcrystalline cellulose (MCC) in binary solvent mixtures of ionic liquids (ILs) and the molecular solvents (MSs) N,N-dimethylacetamide (DMAc) and dimethyl sulfoxide (DMSO). The ILs we used are based on 1-(n-butyl)-3-methylimidazolium cation, BuMeIm+, with acetate (AcO−) and chloride (Cl−) anions. As experimental variables, we changed the mole fraction of the MS (χDMAc or χDMSO) and the temperature (T). MCC dissolution was determined using an optical microscope and expressed on the mass fraction scale (m%). The order of maximum m% was BuMeImAcO-DMSO > BuMeImAcO-DMAc ≫ BuMeImCl-DMSO. To rationalize this dependence, we used molecular dynamics (MD) simulations employing, as a model for cellulose, a crystallite of eight chains, each containing ten anhydroglucose units (AGUs). We calculated the root-mean-square-deviation (RMSD) and the radial distribution function, g(r). Values of RMSD showed that the separation of decamer-chains follows the same order as the maximum m%; more chain separation was taken to indicate greater crystallite dissolution. Additionally, the maximum values and the sharpness of the g(r) peaks followed the same order of dissolution, due to a combination of hydrogen bonding between the hydroxyl groups of the AGU and ions of the IL. We also recorded the turbidity of MCC-IL-DMSO solutions and the conductance of cellobiose-IL-MS solutions; the results of both experiments corroborated our interpretations of the MD simulation results. Our study suggests that MD simulations can be fruitfully employed to predict the best candidates among a series of solvents, e.g., IL-MS. This screening saves labor and material in the search for optimal solvents for cellulose dissolution.

DFT Study of Cl− Ingress into Organic Self-Assembled Monolayers on Aluminum

We address the mechanism by which organic layers on aluminum substrate hinder the penetration of Cl− toward the metal substrate. Localized corrosion by chlorides on Al and its alloys is a major problem, and organic molecules that form self-assembled monolayers on metal substrates may provide efficient corrosion protection. In one of our previous works, we established experimentally that long-chain n-alkyl carboxylic acids form protective layers against Cl− corrosion on Al substrates. In a different work, we identified, using implicit models of the organic layer and metal substrate, two essential effects by which organic layers hinder the penetration of Cl− ions toward the metal substrate. The first effect is due to the inferior solvation of ions in the organic layer compared to that in an aqueous solvent. The second effect is due to the electric field at the electrochemical interface, and the extent to which it affects the penetration of Cl− depends on the electrode potential and the thickness of the organic layer. Both effects are related to a low dielectric constant of the self-assembled monolayer. In the present study, we continue our investigation and explicitly model the organic monolayer and Al substrate using density-functional-theory calculations. To this end, we consider organic monolayers consisting of either dodecanoic- or hexanoic-acid molecules. Current calculations confirm the findings of the simplified implicit models, i.e. the energy barrier for the Cl− penetration increases with the thickness of the organic monolayer and with Cl− concentration in the monolayer. Furthermore, we propose a new mechanism by which Cl− penetrates the organic monolayer. Due to the considerably inferior solvation of Cl− in the organic layer compared to that in water, calculations suggest that it is energetically easier to locally “open” the organic monolayer by creating a hole large enough to accommodate water molecules and Cl−. The presence of water molecules ensures a stronger Cl− solvation and a better electrostatic screening between anions. While the energy barrier for the Cl− penetration via the local “opening” mechanism is suggested to be smaller than for the penetration of Cl− into dense homogeneous organic monolayer, it is still significant enough to pose a considerable kinetic barrier for the penetration of Cl− from the aqueous solution into the organic monolayer at room temperature.

Influence of ball materials on the surface activation behavior of coal ash particles during a mechanochemical process

In this study, the surfaces of coal ash particles were activated via a planetary ball mill-assisted mechanochemical process by utilizing balls that were made from different materials such as zirconia, alumina, and iron. The influence of ball materials on particle morphology, crystallinity, chemical structure, and elution of Si and Al ions in alkali solvents were systematically investigated for the first time, during when the impact energy and friction force induced on the coal ash surface was also clarified in details via the assistance of a self-constructed system. It was found that the mechanochemical process performed with zirconia and iron balls featured a preferred “grinding effect” with decreasing particle size and increasing specific surface area. This was due to the efficiently impact energy induced. In contrast, alumina balls featured an “activation effect” by inducing crystal distortion on the surface and thereby, promoting the ion elution within the alkaline solvents.

Continuous Covalent Organic Frameworks Membranes: From Preparation Strategies to Applications.

Covalent organic frameworks (COFs) are porous crystalline polymeric materials formed by the covalent bonding of organic units. The abundant organic units library gives the COFs species diversity, easily tuned pore channels, and pore sizes. In addition, the periodic arrangement of organic units endows COFs regular and highly connected pore channels, which has led to the rapid development of COFs in membrane separations. Continuous defect-free and high crystallinity of COF membranes is the key to their application in separations, which is the most important issue to be addressed in the research. This review article describes the linkage types of covalent bonds, synthesis methods, and pore size regulation strategies of COFs materials. Further, the preparation strategies of continuous COFs membranes are highlighted, including layer-by-layer (LBL) stacking, in situ growth, interfacial polymerization (IP), and solvent casting. The applications in separation fields of continuous COFs membranes are also discussed, including gas separation, water treatment, organic solvent nanofiltration, ion conduction, and energy battery membranes. Finally, the research results are summarized and the future prospect for the development of COFs membranes are outlined. More attention may be paid to the large-scale preparation of COFs membranes and the development of conductive COFs membranes in future research.

Recent advances in nanomedicine preparative methods and their therapeutic potential for colorectal cancer: a critical review.

Colorectal cancer (CRC) is a prevalent malignancy that affects a large percentage of the global population. The conventional treatments for CRC have a number of limitations. Nanoparticles have emerged as a promising cancer treatment method due to their ability to directly target cancer cells and regulate drug release, thereby enhancing therapeutic efficacy and minimizing side effects. This compilationexamines the use of nanoparticles as drug delivery systems for CRC treatment. Different nanomaterials can be used to administer anticancer drugs, including polymeric nanoparticles, gold nanoparticles, liposomes, and solid lipid nanoparticles. In addition, we discuss recent developments in nanoparticle preparation techniques, such as solvent evaporation, salting-out, ion gelation, and nanoprecipitation. These methods have demonstrated high efficacy in penetrating epithelial cells, a prerequisite for effective drug delivery. This article focuses on the various targeting mechanisms utilized by CRC-targeted nanoparticles and their recent advancements in this field. In addition, the review offers descriptive information regarding numerous nano-preparative procedures for colorectal cancer treatments. We also discuss the outlook for innovative therapeutic techniques in the management of CRC, including the potential application of nanoparticles for targeted drug delivery. The review concludes with a discussion of current nanotechnology patents and clinical studies used to target and diagnose CRC. The results of this investigation suggest that nanoparticles have great potential as a method of drug delivery for the treatment of colorectal cancer.

Simultaneous measurement and ODE-modeling of ion- and water permeability through ion exchange membranes

The determination of diffusion coefficients in solid materials as a measure of particle mobility is of great scientific interest. This applies both to desired diffusion, such as in fuel cell- and dialysis membranes, and to undesired diffusion in insulating materials. In any case, diffusion is a measure of performance. Especially for solvated ions, the permeability of the solvent must also be considered.In this work, a measurement method for the simultaneous determination of coupled ion diffusion and water permeability in polymer membranes is presented. For this purpose, measurement methods for the determination of concentration-, volume- and membrane-potential changes are integrated into a single, miniaturized concentration cell.A system of ordinary differential equations is developed for the general description of the coupled transport processes. This makes it possible to model the interdependent solute concentration and solvent volume changes. The coefficients of interest are defined by fitting the model parameters to the measured data.To evaluate the new combined measurement setup, a freestanding ion exchange membrane with largely known properties is used. The membrane of choice is a Nafion® NR211 membrane, since Nafion® is one of the most investigated PEM in literature and allows a comparison of computational and experimental results with existing data.

RCS reduction using embedded meta-structure absorber in X-band

One approach for lowering radar cross section (RCS) is by reducing reflection, which can be achieved by use of absorbers. Embedded meta-structure absorbers (MSAs) are void of metallic resonating structures, which minimize out-of-band reflections thus reducing the chance of detection by radar systems. Here, an X-band MSA is developed by embedding ionic deep eutectic solvent gel as subwavelength cuboidal resonant structures in flexible silicone rubber. The material properties and structural geometry of the gel combines to enhance the dB absorption bandwidth to more than . The fabricated Gel-Si MSA is sufficiently flexible with an overall thickness of . dB RCS reduction is evaluated in the range over the X-band. The RCS properties are insensitive to polarization angles up to and incident angle up to .

Active pharmaceutical ingredient ionic liquid in natural deep eutectic solvents – Influence of solvent composition

In this work, the mixture of the active pharmaceutical ingredient ionic liquid (API-IL) benzocainium ibuprofenate and natural deep eutectic solvents (NADESs) of menthol:decanoic acid with the molar ratios 1:2, 1:1 and 2:1 were prepared, and nature of interactions in these systems was investigated for the first time. These systems of hydrophobic API-IL-NADES are mixtures that are compatible and offer an opportunity for the topical application of ionic liquids, which are in a liquid state above room temperature and do not dissolve in water well. Ionic liquid and NADESs with different molar ratios were synthesized and characterized using infrared and nuclear magnetic resonance spectroscopy and differential scanning calorimetry. The densities, speeds of sound, and viscosities of the studied mixtures were measured in the temperature range from T = (293.15 to 318.15) K at different API-IL molalities. From obtained thermodynamic properties, it was discussed how the mole fraction of the NADES components influences the molecular and solvent performance.

Tuning functional ionic deep eutectic solvents as green sorbents and catalysts for highly efficient capture and transformation of CO2 to quinazoline-2,4(1H,3H)-dione and its derivatives

A series of functional ionic deep eutectic solvents (iDESs) containing pyridinolate anions were reported as green sorbents, solvents, and catalysts for highly efficient capture and transformation of CO2 to quinazoline-2,4(1H,3H)-dione and its derivatives at mild conditions via tuning the structures of iDESs. Physical properties, such as density and viscosity, as well as flow activation energy and thermal expansion coefficient, were systematically investigated. Effects of the partial pressure of CO2 and the absorption temperature on the CO2 absorption capacity using these functional iDESs as sorbents were studied, and the different absorption mechanisms, including carbamate and carbonate pathways, were analyzed by FT-IR and 13C NMR spectroscopy. Additionally, thermodynamics analysis of CO2 absorption was performed according to the chemical reaction mechanism, and Kθ,ΔrGθm), ΔrHθm, and ΔrSθm were calculated. Furthermore, the effects of cations, anions, HBDs, reaction temperature, and the molar ratio of catalyst to substrate (nCat./nSub.) on CO2 conversion were systematically studied, and excellent isolated yield of up to 97.1% at mild conditions could be obtained with only 0.25 equiv. DES as the solvent as well as the sorbent and the catalyst. Plausible “simultaneous CO2 activation and substrate activation” reaction mechanism of capture and transformation of CO2 to quinazoline-2,4(1H,3H)-diones by [N2222][4-PyO]/DMSO (1:4) was verified by the spectra of FT-IR and based on previous reports. To the best of our knowledge, these are the first examples of tuning functional iDESs for the capture and transformation of CO2 to quinazoline-2,4-(1H,3H)-dione and its derivatives with only 0.25 equiv. DES. The method may also open a door to obtain the high efficiency of capture and transformation of such gases as NOx, SO2, CO, H2S, and CO2 by functional DESs.

Recent Applications and Prospects of Nanowire-Based Biosensors

High-sensitivity biomedical sensors could make it possible to detect and classify chemical and biological species in a variety of applications, from disease diagnosis to medication discovery, thus, boosting the likelihood of life-saving intervention. Synthesized nanowires have already produced advancements in a variety of sectors, including biological sensors over the last decade. When compared to macro-sized materials, the nanowires’ large surface area-to-volume ratio increased sensitivity. Their applications for biomarker, viral, and DNA detection, as well as drug discovery, are also discussed. Self-powering, reusability, sensitivity in high ionic strength solvents, and long-term stability are all examples of recent developments. Shortly, the nanowire is likely to lead to major improvements in biomedical sensors. This review provides a full overview of the nanowire sensor’s working principle and production procedure. We have discussed how to produce nanowires that can be utilized as biosensors for different bacteria and pathogens, protease, DNA and RNA, neurotransmitters, and chemical compounds. Biosensing technology has dramatically improved because of the introduction of nanowires in biosensors. This is a result of the application of new biorecognition components and transducers, improvements in the manufacture, design, and miniaturization of nanostructured devices at the micron scale, and unique approaches for the synthesis of nanowires. The versatility, robustness, and dynamic nature of sensing technologies have all improved thanks to the usage of nanowires.