Ion Association Research Articles

THE POSSIBILITY OF EFFECTIVE USE OF BASIC DYES OF THE "BAZAKRYL" TRADEMARK IN THE DETERMINATION OF ANIONIC SURFACTANTS

This study shows the prospects of using "Bazacryl" brand dyes in spectrophotometric analysis. On the basis of previous studies, their main spectrophotometric and protolytic characteristics have already been established, which made it possible to find out the optimal conditions for the formation of ionic associates of anionic surfactants with "Bazakrils". The studied dyes are characterized by a sufficiently high color intensity within a wide range of changes in the acidity of the medium, and in terms of these properties, they are not inferior to the majority of known basic dyes used in analytical practice. The kinetic factors of extraction were studied. As a result, the extraction equilibrium is established after 10-30 seconds of mixing the phases and practically does not depend on the used extractant, but 1-3 min. centrifugation is sufficient for complete phase separation. The optical density of the extracts of the formed IA does not change within 2 hours. It was established that such dyes show the ability to form IA from APAR and can serve as analytical reagents for their determination. The optimal conditions for the formation and extraction of IA APAR with new dyes have been established. A new, simple and rapid method for determining APAR in various samples of wastewater and natural waters, detergents, etc. is proposed.
 Keywords: dyes; spectrophotometry; ionic associate; protolytic properties; spectrophotometric properties.

Determination of the Ionic Association Constants of Na+ with CO32- and HCO3- Ions, in NaCl-NaHCO3-H2O Ternary Systems, at 25 °C.

The ionic association constants of sodium with carbonate ion (K1C') and acidic carbonate ions (K2C') were measured in NaCl-NaHCO3-H2O ternary systems to determine the distribution of sodium among the chemical species present in the growth medium of Chlorella homosphaera 424 algae. The mean activity coefficients of sodium chloride (in pure sodium chloride and in a mixture of electrolytes) were determined experimentally using two electrochemical cells, namely Ag, AgCl| KCl (3 M)|| NH4NO3 (1 M)| NaCl (mNaCl)| Na+-ISE and Ag, AgCl|KCl (3 M)|| NH4NO3 (1 M)| NaCl (mNaCl)| Cl--ISE. The studies carried out show that the values of the association constants of K1C' and K2C' do not depend on the composition of the medium, but only on the effective ionic strength. The experimentally obtained γNaCl0 values in the binary system are comparable to the mean activity coefficients values for NaCl, calculated using data from the literature, with -0.9 to 0.1% relative standard deviation. The obtained results show that the experimentally determined mean activity coefficient in the ternary system, γNaCl, is smaller than γNaCl0 in the binary system over the entire field of ionic strengths studied. The ternary system NaCl-NaHCO3-H2O obeys Harned's rule.

Modeling aqueous association constants and mineral solubilities at subcritical and supercritical temperatures

The need for sustainable power generation has increased interest in the use of hydrothermal fluids for industrial applications. New high-enthalpy geothermal systems and biowaste-to-fuel processes are two relevant examples that employ supercritical fluids which require an in-depth understanding of complex chemical reactions occurring near the supercritical temperature of water (374 °C). As these processes operate in thermodynamic regimes that are not currently covered by a standard molar Gibbs energy of formation model, only empirical fits for single reaction systems are available which limit the use of multi-component phase equilibria calculations that are standard practice for less extreme environments. Here, we advance a standard molar Gibbs energy of formation model able to operate in these otherwise inaccessible thermodynamic states to include species needed for key mineral solubility systems and ion association reactions. This work extends a model based on molecular statistical thermodynamics (MST) into four new systems (Na3PO4-H2O, LiOH-H2O, KOH-H2O, and BaSO4-H2O) by extending the model to cover 10 new species. For each of these systems, model predictions were consistently within the experimental uncertainties for the new systems covered. A breakdown of MST contributions to the model revealed that electrostatic and hard sphere contributions were key to reproducing density dependencies of standard molar Gibbs energy of formation values around the critical point of water.

Rapid Colorimetric Determination of Biologically Active Organic Analytes

Four types of reactions (azo coupling, protolytic and oxidative condensation, ion association), accompanied by the formation of hydrophobic colored analytical forms of corresponding organic analytes, are proposed on an example of biologically active substances (aromatic amines, α-amino acids, antibiotics of aminoglycoside and β-lactam series, anionic surfactants). It is shown that, in these systems, the hydrophobicity of both the initial reactants, e.g., tetrafluoroborates of diazonium salts, and analytical forms (azo compounds, Schiff bases, Ruemann’s purpura, ion associates with surfactants) can be increased. Possibilities of various methods for the derivatization of organic analytes with the formation of colored analytical forms with increased hydrophobicity for the best fixation on solid matrices and the development of test systems on their basis, which can be used to control the quality of various samples with rather good performance characteristics, are considered.

Characterization of Divalent Metal Soaps of Cannabis Sativa Seed Oil

In this study, the structural characteristics and thermal degradation behaviour of barium, calcium and zinc soaps of hemp seed oil prepared using the metathesis method are reported. Scanning electron micrographs of the metal soaps showed similar plate-like microstructures and are indicative of an orderly packed particulate structure. The bands at 1509, 1539 and 1543 cm-1 in the FTIR spectra showed the association of the carboxylate ion with Ba, Ca and Zn ions respectively The thermal decomposition consisted of one single step on the weight loss – temperature curves located around 250 – 450 oC for all the divalent metal soaps at the various heating rates and the observed loss in weight which occurred before 200 oC was minimal (< 10%). The average values of the apparent activation energy for the thermal process were 18.73, 13.77 and 8.48 kJ/mol for Zn-HSO, Ca-HSO and Ba-HSO respectively.

Understanding the Catalytic Mechanism of Redox Mediators for Li-O2 Batteries Using Cyclic Voltammetry

Lithium-air batteries are appealing candidates for high-energy electric vehicle applications because they have a theoretical capacity 3 to 5 times higher than li-ion batteries. They are composed of a lithium anode and a porous conductive matrix (usually carbon-based), where oxygen is reduced during discharge and oxidized during charge. One of the major issues is the high overpotentials needed to recharge the battery due to the isolating nature of the solid discharge product, lithium peroxide.The use of redox mediators (RMs) for the discharge and charge reactions has gained popularity because it can increase energy efficiency and minimize electrolyte degradation. These molecules act as soluble catalysts: during the discharge, the RM molecule is reduced at the surface of the electrode; it then diffuses through the solution where it can react with solubilized oxygen to form big solid deposits of Li2O2. In the case of charge, the RM is oxidized at the free surface of the electrode that is not blocked by Li2O2, and then chemically reacts with it to release O2. Thus, RMs allow decoupling of the oxygen reduction reaction oxygen evolution reaction from the electron transfer (ET) reactions at the electrode, giving the charge transfer an alternative path to the electrically insulating Li2O2.1 Previous studies have mainly focused on the thermodynamic aspects governing the ability of a molecule to act as a successful RM. The principal parameter analysed is usually the standard potential of the electrochemical couple, although oftentimes it is poorly characterized using inadequate reference electrodes or assumed to be independent of the solvent, Li salt concentration and identity. Some attention has been given to the effect of solvation environments on the potential of iodide,2 but little has been said about other RMs.3 Since most ET reactions with RMs involve a significant change in the charge/size ratio of the molecule or ion, it is only natural that the driving force for this reaction will be dependent on the environment.The kinetics of the ET and of the reaction of RM with the target species (O2 in the case of discharge RM and Li2O2 in the case of charge) is another factor that has received almost no attention, and yet it is crucial for the operation of a Li-O2 battery. Some effort has been made to relate the kinetics of the catalysis to the standard potential of the RM or the ET kinetics,4 but there is no consensus regarding these effects. No rationalization of the effect of solvation environments such as ionic association or DN of the solvent on the kinetics has been established either.Cyclic voltammetry (CV) is a very useful tool to probe the kinetics both of electrochemical reactions and chemical reactions. It is possible to decouple the influence of these two types of processes by varying the scan rate. Furthermore, the effect of ionic association and solvation environment become easily identifiable in CVs. We show how these parameters affect simulated experiments, and how this can facilitate the understanding of the processes limiting the performance of a cell. Moreover, we can use this approach to extract semiquantitative information about the catalytic mechanism both for charge RM and discharge RM by comparing it with experimental data.To benchmark our simulations, the electrochemical behaviour of two typical RMs was studied. 2,5-di-tert-butyl-1,4-benzoquinone (DBBQ) and lithium iodide were used as discharge and charge redox mediator models, respectively. This way, we evidenced the effect of different solvents and of ionic association on CVs, and we showed that the effect of the chemical reaction between triiodide and Li₂O₂ becomes more important at slow scan rates (<1 mV/s). Using this approach, we were able to probe the timescales of the catalytic behaviour of triiodide and relate it to the performance of mediated lithium-oxygen batteries at different charge rates.The advantage of this approach is that it is easily generalizable to other kinds of RMs, without the need of following specific functional groups that depend on the structure of the molecule. This will allow for quantitative information to be obtained about the catalytic behaviour, and aid the understanding of catalytic mechanisms of Li-O2 batteries. Further implementation of this method will be aimed at establishing relationships between the catalytic and the thermodynamic parameters.

Photoinduced Processes in Molecular and Supramolecular Arrays Based on Porphyrins and Acridinium Units

Multichromophoric arrays based on porphyrins are of high interest for their mimicry of naturally occurring photoinduced energy and electron transfer processes leading to energy collection and conversion. [1] Moreover, the rich photophysics and electrochemistry of porphyrins make them suitable components of molecular wires, switches or chemical sensors. [2] In this perspective, it is interesting to pursue the combination of porphyrins with units that can act as multiresponsive components by modifying their chemical and electronic structure upon chemical or redox stimuli. N-acridinium ions have been recently explored as a new class of switches that respond to various orthogonal stimulations (pH or electrochemical/photochemical inputs) that trigger their reversible conversion into the non-aromatic acridane form. [3] Few examples reporting the association of acridinium units and porphyrins indicate that these systems are characterized by fast photoinduced electron transfer reactions between the porphyrin donor and the acridinium acceptor. [4,5]We recently investigated the photophysical properties of molecular and supramolecular arrays based on porphyrins and acridinium units, where the type of porphyrin (free-base or metallated) and/or the form of the switchable component (acridinium or acridane) has been varied (Figure 1). We found that the association of porphyrins and acridinium ions always leads to ultrafast electron transfer processes, and that these reactions can be altered by changing the temperature or by converting the acridinium electron acceptor into an acridane energy donor. Moreover, the combination of two Zn-porphyrins with two acridinium/acridane units results in switchable molecular receptors able to coordinate suitable hosts. The photophysics of the arrays and of the complexes, analyzed by means of steady-state and time-resolved luminescence techniques and ultrafast transient absorption spectroscopy, will be herein presented and discussed.The work is supported by the H2020-MSCA-ITN-2017-765297 project “NOAH” and by the H2020-LC-SC3-2020-RES-RIA-101006839 project “CONDOR”.[1] M. Beyler, L. Flamigni, V. Heitz, J.-P. Sauvage, B. Ventura, Photochem. Photobiol. 2014, 90, 275-286.[2] Beletskaya I, Tyurin VS, Tsivadze AY, Guilard R, Stern C. Chem. Rev. 2009, 109, 1659-1713.[3] H.-P. J. de Rouville, J. Hu, V. Heitz, ChemPlusChem, 2021, 86, 110-129.[4] A. Edo-Osagie, D. Sánchez-Resa, D. Serillon, E. Bandini, C. Gourlaouen, H.-P. Jacquot de Rouville, B. Ventura, V. Heitz, C. R. Chim. 2021, 24, 1-9.[5] H. Kotani, K. Ohkubo, M. J. Crossley, S. Fukuzumi, J. Am. Chem. Soc., 2011, 133, 11092-11095.Figure 1. Structures of the studied arrays and schemes of the occurring photoinduced processes: a) bisacridinium-Zn(II) porphyrin conjugate, b) bisacridinium-diphenylporphyrin conjugate, c) bis(acridinium/acridane)-Zn(II) porphyrin receptors. Figure 1

In Silico Simulations Reveal Molecular Mechanism of Uranyl Ion Toxicity towards DNA-Binding Domain of PARP-1 Protein.

The molecular toxicity of the uranyl ion (UO22+) in living cells is primarily determined by its high affinity to both native and potential metal-binding sites that commonly occur in the structure of biomolecules. Recent advances in computational and experimental research have shed light on the structural properties and functional impacts of uranyl binding to proteins, organic ligands, nucleic acids, and their complexes. In the present work, we report the results of the computational investigation of the uranyl-mediated loss of DNA-binding activity of PARP-1, a eukaryotic enzyme that participates in DNA repair, cell differentiation, and the induction of inflammation. The latest experimental studies have shown that the uranyl ion directly interacts with its DNA-binding subdomains, zinc fingers Zn1 and Zn2, and alters their tertiary structure. Here, we propose an atomistic mechanism underlying this process and compute the free energy change along the suggested pathway. Our Quantum Mechanics/Molecular Mechanics (QM/MM) simulations of the Zn2-UO22+ complex indicate that the uranyl ion replaces zinc in its native binding site. However, the resulting state is destroyed due to the spontaneous internal hydrolysis of the U-Cys162 coordination bond. Despite the enthalpy of hydrolysis being +2.8 kcal/mol, the overall reaction free energy change is -0.6 kcal/mol, which is attributed to the loss of domain's native tertiary structure originally maintained by a zinc ion. The subsequent reorganization of the binding site includes the association of the uranyl ion with the Glu190/Asp191 acidic cluster and significant perturbations in the domain's tertiary structure driven by a further decrease in the free energy by 6.8 kcal/mol. The disruption of the DNA-binding interface revealed in our study is consistent with previous experimental findings and explains the loss of PARP-like zinc fingers' affinity for nucleic acids.

Complex extraction of sulfonate dyes from wastewater and the effect of dye structure on extraction performance

ABSTRACT In this study, the influences of sulfonate dye structure on the extraction rate, the reaction mechanism, and the complex ratio were studied. The parent structure and the number of sulfonic acid groups of sulfonate dyes have a great effect on extraction performance, whilst the molecular weight has a small effect on extraction performance. The results indicate that the extraction rate of azo dyes remains above 80% at the aqueous-organic phase ratio of 7:1, but the extraction rate of two anthraquinone dyes decreases to 54.9% and 34.9%, respectively; and the fewer the number of sulfonic acid groups of the dye, the better the extraction performance under the condition of insufficient extractant, the extraction rate of Direct Grey D and Acid Red M is over 82%. A complete set of methods for determining the ratio of the extractant and the dye was determined using the distribution coefficient method. The interaction between Telon Yellow 4 R and trioctylamine is ionic association and hydrogen bonding association, and the complex ratio between the dye and the extractant is about 2:1. In summary, dye structure has a big impact on the extraction performance, which should be taken into account in actual application.

Super-enrichment of ultra-low concentration rhenium via synergistic co-flocculation precipitation using CTAB and ferric salt hydrolysis micelles

Super-enrichment and recovery of associated Rhenium (Re) in sandstone-type uranium deposits is challenging due to its sparse distribution and ultra-low contents in raw ores. Conventional industrial processes are extremely difficult to achieve economic recovery of Re with a concentration below 0.1 mg/L from in-situ leaching solutions of sandstone-type uranium deposits. This study proposes a novel approach for achieving super-enrichment ultra-low concentration of Re using a synergistic co-flocculation precipitation system composed of cetyltrimethylammonium-bromide (CTAB) and ferric salt (FeCl3) hydrolysis micelles. Experimental results reveal that the enriched content of Re in the co-flocculation precipitates is as high as 503 g/t, nearly 3353 times higher than that in the in-situ leaching solutions. The synergistic precipitation percentage of Re can reach more than 60%, which is larger than the sum of using CTAB micellar flocculation (30.16%) and FeCl3 hydrolysis micellar flocculation (5.43%) separately. Furthermore, the synergistic co-flocculation and precipitation mechanism of Re is examined by SEM, turbidity, Fourier transform infrared spectroscopy, Zeta potential analysis, and DTF calculations. Results demonstrate that the ReO4- anions first form ion associations with CTA+ cations through electrostatic force, which are subsequently captured to forms insoluble co-flocculating precipitate via weak intermolecular hydrogen bond force between Fe(OH)3 and ReO4-, which promotes the super-enrichment of the ultra-low concentration Re. In summary, this process presents great potential for the efficient recovery Re from a large amounts of sandstone-type uranium deposits leaching solution, and provides new insights into the enhancement mechanism of synergistic co-flocculation precipitation.

Role of water structural properties in interaction of amino acids with metal ions of varying size and electrons in d-block or main group elements: Quantitative thermodynamic analysis

Interactions of a homologous series of amino acids (glycine, l-alanine, DL-α-amino-n-butyric acid, l-valine and l-leucine) with salts (LiCl, NaCl, KCl, CaCl2, MnCl2, CoCl2) having common anion, but cation having varying d-electronic configuration and alkaline earth metals have been studied in aqueous solutions employing ultrasensitive isothermal titration calorimetry. Standard molar enthalpies of amino acid-salt interactions have been interpreted in terms of predominant ionic association between charged centres and the corresponding desolvation penalty. Extra crystal field stabilization experienced by Mn2+(aq) and Ca2+(aq) due to d5 and d10 electronic configuration has been addressed based on results of standard molar enthalpies of interaction. The results indicate significant desolvation cost predominantly from hydration of the cations of the salts rather than from hydration of zwitter-ionic ends of the amino acids irrespective of their chain length. This is also indicated by stronger endothermic interaction of the amino acids with the bivalent cations than that with the monovalent ones. The results obtained in this work provide essential mechanistic insights into nature of amino acid interactions modulated by variation in cationic d-electronic configuration in terms of enthalpies of interaction.

Atomic insights into the heterogeneity and the interface interactions of nanoconfined aqueous electrolyte solution

The structure and properties of nanoconfined electrolyte (nano electrolyte) solutions are important subjects in biochemistry, electrochemistry, separation science, etc. In the present work, neutron scattering and data driven reverse Monte Carlo were employed to quantitatively reveal the microstructure of aqueous CaCl2 solution in mesoporous silica MCM-41 at the atomic level. The electrolyte solution distributes in-homogeneously in the pores of mesoporous silica along the radial direction, which can be divided into the core, the transition, and the interface regions. The hydrogen bond structure of water in nano electrolytes is strengthened in the core region, analogous to that of nano water confined in nanochannels, and the ion association was enhanced in the transition region. The structure of the solution in the interface region was analogous to the bulk electrolyte solution under high pressure because of the confinement and interface effects. When the package ratio of nano electrolyte solution is insufficient, small amount of solution quasi-monolayer adsorb on the internal surface of mesoporous silica, the majority solution preferentially forms clusters with different sizes to adhere to the wetted interface. The anomalous hydrogen-bonding structure and ion association found in the present work improve our understanding of nanoconfined electrolyte solutions.

Optimizing Li-ion Solvation in Gel Polymer Electrolytes to Stabilize Li-Metal Anode.

Gel polymer electrolytes (GPEs) have potential as substitutes for liquid electrolytes in lithium-metal batteries (LMBs). Their semi-solid state also makes GPEs suitable for various applications, including wearables and flexible electronics. Here, we report the initiation of ring-opening polymerization of 1,3-dioxolane (DOL) by Lewis acid and the introduction of diluent 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE) to regulate electrolyte structure for a more stable interface. This diluent-blended GPE exhibits enhanced electrochemical stability and ion transport properties compared to a blank version without it. FTIR and NMR proved the effectiveness of monomer polymerization and further determined the molecular weight distribution of polymerization by gel permeation chromatography (GPC). Experimental and simulation results show that the addition of TTE enhances ion association and tends to distribute on the anode surface to construct a robust and low-impedance SEI. Thus, the polymer battery achieves 5 C charge-discharge at room temperature and 200 cycles at low temperature -20 °C. The study presents an effective approach for regulating solvation structures in GPEs, promoting advancements in the future design of GPE-based LMBs.

New insights into the nucleation of portlandite and the effects of polymeric additives

The crystallization of calcium hydroxide (Ca(OH)2, CH, portlandite) is a key process during the early stages of cement hydration. In the present work, we have revisited the formation of this mineral through nucleation and growth from supersaturated aqueous solutions, in the light of the currently emerging picture of multistage “non-classical” crystallization. To that end, we developed a titration-based assay, in which stock solutions of both relevant ions are added simultaneously into a reservoir, where supersaturation increases slowly at constant stoichiometry until nucleation occurs. This procedure allows both pre- and early post-nucleation phenomena to be analyzed quantitatively. Complementarily, the early stages of portlandite mineralization were probed by various advanced characterization techniques, including cryo-transmission electron microscopy (cryo-TEM), in-situ small-angle X-ray scattering (SAXS), pair distribution function (PDF) analysis of high-energy X-ray scattering (HEXS) data, and analytical ultracentrifugation (AUC). The experimental data show that the formation of calcium hydroxide starts with the association of ions into complexes and clusters, which subsequently coalesce to form amorphous nanoparticles – much like what has been observed in the case of calcium carbonate and other prominent minerals. Subsequently, these particles aggregate and build networks, which eventually transform into hexagonal Ca(OH)2 crystals. The presence of a soluble polycarboxylate – as a known inhibitor of portlandite crystallization – does not change the main characteristics of this multistep nucleation pathway, but it proved capable of significantly extending the lifetime of the amorphous intermediate phase and thus delaying the transition to the final crystalline phase. Our observations confirm the notion that “non-classical” crystallization is a much more common phenomenon than initially believed – and that, for minerals forming in aqueous environments, it may actually be the rule rather than the exception.

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.

Electrical Conductivity and Ionic Association in Tetraalkylammonium Ionic Liquids in Acetonitrile Solutions

A study is performed of the electrical conductivity (EC) of ionic liquids based on quaternary triethylalkylammonium salts with tetrafluoroborate and hexafluorophosphate anions in acetonitrile. Conductometric data on these compounds are analyzed. Constants Ka of the ionic association of the limiting molar electrical conductivity (λ0) and the standard Gibbs energy of association (ΔG0) in solutions are calculated using the Lee–Wheaton formula. The Stokes radii, limiting mobility, and limiting coefficients of diffusion are found for tetraalkylammonium cations.

Ion pair and larger ion cluster formation in water interfacial regions: An atomic force microscopy study

Interfacial regions attached to hydrophobic and hydrophilic surfaces have very low relative permittivities (ε ∼ 3–5), and these low values induce the formation of ion pairs. A detailed description of ion pairing will be possible only after the development of adequate experimental probing methods. The scheme described in this work detects the ion pair (or multistage ion association) formation in water solutions in the interfacial region. Forces acting on the tip when immersed in the interfacial region attached to hydrophilic substrates, such as mica where ε &amp;lt; 7, are attractive (AFM tip dielectric constant = 7). These attractive force steps with extensions equal or smaller than the Bjerrum length at hydrophilic substrates are associated with ion pair formation in interfacial regions. Measurements show that the interfacial water molecular arrangement and ion pairs form an ordered structure (ε &amp;lt; 7) induced by mica interfacial charges. The interfacial region attached to hydrophobic substrates, however, form separated arrangements of ion pairs and water molecular structures as observed by the repulsive steps (ε &amp;gt; 7) intercalated in between attractive regions (ε &amp;lt; 7).

Analysis of Activity Coefficients in Aqueous Solutions of Alkali Metal Bromides Based on Dielectric Properties

Extended Debye–Hückel (EDH) theory was used to calculate activity coefficients in aqueous solutions of alkali-metal bromides at 298 K from experimentally determined values of their static permittivities. Calculations with non-optimized model parameters fit the nonmonotonic concentration-dependent trend of the activity coefficients and the cation radius–dependent trend of the activity coefficients. The latter is explained by hydration weakening and ion association strengthening in response to increasing cation radius in the salt series.

A multifunctional and sustainable poly(ionic liquid)-quaternized chitosan hydrogel with thermal-triggered reversible adhesion

A quaternized chitosan (QCS)@poly(ionic liquid) (PIL) hydrogel adhesive was prepared by in-situ ultraviolet (UV)-induced copolymerization of 1-vinyl-3-butyl imidazolium bromide ([BVIm][Br]) and methacryloyloxyethyl trimethylammonium chloride (DMC) in QCS aqueous solution without using any crosslinkers, which was stably crosslinked by reversible hydrogen bonding together with ion association and exhibited excellent adhesion, plasticity, conductivity and recyclability properties. Moreover, its thermal/pH-responsive behaviors and intermolecular interaction mechanism of thermal-triggered reversible adhesion were discovered, meanwhile good biocompatibility, antibacterial properties, repeated stickiness and degradability were also proved. The results showed that the newly developed hydrogel could make various tissues, organic, inorganic or metal materials adhered tightly within 1 min; after 10 binding-peeling cycles, the adhesive strength to glass, plastic, aluminum and porcine skin still remained beyond 96 %, 98 %, 92 % and 71 % of the original, respectively. The adhesion mechanism involves ion dipole interaction, electrostatic interaction, hydrophobic interaction, coordination, cation-π interaction, H-bonding and van der Waals force. For above merits, the new tricomponent hydrogel is expected to be applied in biomedical field to achieve adjustable adhesion and on-demand peeling.

Structure of the Nearest Environment of Ions in Aqueous Solutions of Cadmium Chloride and Nitrate According to the Data of X-ray Diffraction Analysis

Quantitative characteristics of the nearest environment of ions in aqueous solutions of cadmium chloride and nitrate are determined by X-ray diffraction analysis in a wide range of concentrations under standard conditions. It is found that, in the studied systems, the coordination number of the cation increases with dilution from 4 to 6. The structure of solutions in the entire studied range of concentrations is determined by ionic associates of the contact type. In solutions of cadmium nitrate, the nitrate ion is monodentately coordinated to the cation.