Halide Solutions Research Articles

Systematic Analysis on Ionic Conductivity of LiBH4 Infiltrated into Mesoporous Scaffolds

It has been known that LiBH4 has a hexagonal crystal structure with a high ionic conductivity (~ 10-3 S/cm) above ~ 110 ℃, although it undergoes a reversible phase transformation to an orthorhombic crystal structure with a low ionic conductivity (~ 10-8 S/cm) below the phase transition temperature. So, many researchers attempted to extend the stability region of the high temperature phase up to room temperature by making a solid solution of LiBH4 and lithium halides. Another route to increase the ionic conductivity of LiBH4 is nanoconfinement. The confinement of LiBH4 in the mesoporous scaffolds amorphizes the structure raising the ionic conductivity as high as ~ 10-4 S/cm even at room temperature. However, it is still unclear which mechanism, i.e. nanoconfinement or generation of interface between LiBH4 and SiO2, governs the ionic conductivity enhancement of infiltrated LiBH4. We therefore systematically investigate the ionic conductivity of LiBH4 and a mesoporous silica (here MCM-41) composite system. In order to separate the effect coming from nanoconfinement and interface, as-purchased MCM-41 was hand-mixed with LiBH4 in one case while in the other case mesopores of MCM-41 was intentionally destroyed by high-energy ball-milling. Interestingly, ionic conductivity of ball milled LiBH4 – MCM-41 mixture turned out to be ~ 10-5 S/cm, which is smaller than that of LiBH4 infiltrated into MCM-41 but it is 1000 times higher than that of pure LiBH4. The result highlights the importance of interface effect and indicates that significant enhancement in ionic conductivity can be achieved through interface engineering. To further exploit the interface effect, volume fraction of LiBH4 was systematically varied, and other kinds of compounds were tested. We believe that such approach can be useful for designing a fast ionic conductor for lithium ion battery.

Skin Absorption of Anions: Part Two. Skin Absorption of Halide Ions.

The purpose of the study was to sort skin penetration of anions with respect to their properties and to assess their mechanisms of penetration. Aqueous solutions of halides at two concentrations were prepared and quantitative penetration studies were carried out for 24h using Franz diffusion cells. The iodide permeation was also measured after blocking of anion channels and transporters to investigate the role of this specific transport. Absorption of halide ions into skin revealed large differences of transport between these anions according to the Hofmeister series. Increasing steady-state fluxes and lag times in the order F(-) < Cl(-) < Br(-) < I(-) were observed in permeation experiments. The steady-state fluxes were proportional to the concentration for each halide ion. Longer lag times for iodide or bromide ions were explained by the ability of such sticky chaotropic anions to interact with apolar lipids especially in the stratum corneum. Inhibiting ion exchangers and channels decreased the flux of iodide ions by 75%, showing the high contribution of the facilitated transport over the passive pathway. Ions transport had contributions coming from passive diffusion through the skin layers and transport mediated by ion channels and binding to ion transporters.

Anion-directed self-assembly of a 2,6-bis(2-anilinoethynyl)pyridine bis(amide) scaffold

Bis(sulfonamide) receptors based on the 2,6-bis(2-anilinoethynyl)pyridine scaffold form persistent dimers with water and halides in solution and in the solid-state. The structurally related bis(amide) receptor derived from 3,5-dinitrobenzoyl chloride is a dimer in the solid-state with two HCl molecules directing the self-assembly. The 2+2 dimer, with a twisted ‘S’-shaped backbone, is held together by six hydrogen bonds. Dissolution of the (H2+√Cl − )2 adduct in CHCl3 results, however, in a monomeric structure. DOSY and 1H NMR experiments were used to identify the dominance of monomer in solution for both 2 and H2+√Cl − . The ‘OFF–ON’ fluorescence response of 2,6-bis(2-anilinoethynyl)pyridine is retained with amide arms.

Mass spectrometry of oligopeptides in the presence of large amounts of alkali halides using desorption/ionization induced by neutral cluster impact.

Oligopeptides in the presence of large amounts of salt were desorbed and ionized using desorption/ionization induced by neutral clusters (DINeC) for further analysis by means of mass spectrometry (MS). Using oligopeptides in alkali halide solutions as a model system, DINeC was shown to yield clear and fragmentation free mass spectra of the biomolecules even from environments with a large excess of salt. The results were traced back to a phase separation between salt and biomolecules during sample preparation. The ratio between alkali metal complexes [M+A](+) and bare biomolecules [M+H](+) was controlled using different preparation schemes. DINeC was applied to the products of a tryptic digest of bovine serum albumin in the presence of sodium chloride; the results of a mass fingerprint analysis did not show a major difference for the spectra with and without salt in the original solution. The metal-ion/peptide interaction was further investigated by means of tandem-MS.

Solvation structure around ruthenium(II) tris(bipyridine) in lithium halide solutions.

The solvation of the ruthenium(II) tris(bipyridine) ion ([Ru(bpy)3]2+) is investigated with molecular dynamics simulations of lithium halide solutions in polar solvents. The anion distribution around the [Ru(bpy)3]2+ complex exhibits a strong solvent dependence. In aqueous solution, the iodide ion forms a solvent shared complex with [Ru(bpy)3]2+, but not in the other solvents. Between Cl– and [Ru(bpy)3]2+, the strong hydration of the chloride ion results in a solvent separated complex where more than one solvent molecule separates the anion from the metal center. Hence, tailored solvation properties in electrolytes is a route to influence ion-ion interactions and related electron transfer processes.

Direct synthesis of hydrogen peroxide with no ionic halides in solution

We efficiently obtain 10 wt% H2O2 solutions by direct synthesis without using ionic bromide promoters.

Investigating the light stability of solid-solution-based AgCl-AgBr and AgBr-TlI crystals

For the development of mid-infrared fiber-optical elements, one needs light-stable, flexible materials that are transparent within this spectral band. Solid solutions of silver and monadic thallium halides prove to be the most suitable crystalline media for these needs. We study the light stability variation of high-purity AgCl1?xBrx (0≤x≤1) and Ag1?xTlxBr1?xIx (0≤x≤0.05) crystals by measuring the optical transmission change as functions of the composition and UV exposure time. The former is executed in a broad spectral range from 6500?350 cm?1, within which we choose three wavelengths to trace the transmission change. For thallium-monoiodide-containing samples, an effect is observed that we assumed to be translucence.

Electrolyte Jet Machining of Titanium Alloys Using Novel Electrolyte Solutions

Electrolyte Jet Machining (EJM) is a non-contact machining process whereby material is removed through highly localised electrochemical dissolution. Throughout the development of this technique, difficulties have been reported in the processing of titanium alloys due to the formation of an electrochemically inert non-conductive passivating layer. In this study, various electrolytes are investigated for the purpose of establishing more stable machining and controlled removal of the passivating layer. Surface finish, material removal rate and pit formations using solutions of sodium halides (bromide, chloride and fluoride respectively) are compared with those obtained using the more commonly used sodium nitrate solution. The concentration of electrolyte is varied in order to appraise the efficacy of each solution. Machined features produced are subject to typical characterisation methods. The removal mechanism for overcoming the passivating layer and the development of more stable machining regimes are explored. Sodium chloride machining is shown to increase mass removal rates by over 100% at concentrations less than 2.5M compared with that achievable using the commonly used sodium nitrate electrolyte. Doping sodium chloride electrolytes with sodium fluoride decreases the overcut effect in machined pits by half compared with the pits formed in chloride, bromide, and nitrate electrolytes.

Single-Step Synthesis of Halogenated Graphene through Electrochemical Exfoliation and Its Utilization as Electrodes for Zinc Bromine Redox Flow Battery

We have demonstrated a single step synthesis of halogen functionalized graphenes (HGs) through electrochemical exfoliation of graphite in aqueous potassium halide solutions. Few layers of as-synthesized HGs are characterized using powder X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Electron paramagnetic spectroscopy (EPR), Brunauer-Emmett-Teller (BET) surface area analysis, Field emission scanning electron microscopy (FESEM), and Transmission electron microscopy (TEM). The degree of halogenation is found to vary between 2.32 and 0.26 atomic % in fluorinated graphene (FG) and iodinated graphene (IG) respectively, which could be attributed to the difference in reactivity of the halogen species generated during the exfoliation process. A suitable mechanism is proposed in accordance with the exfoliation phenomena and functionalization of halogens on the graphene sheets based on the experimental observation. As synthesized HGs are utilized as electrode materials for zinc bromine flow batteries (ZBB) and the electrocatalytic effect of HGs electrodes for the 2Br−/Br2 redox couple has been investigated in detail. Cyclic voltammetry (CV), and charge-discharge studies were carried out to study the electrochemical performance of the HGs. Among all HGs, FG has shown the superior electrocatalytic behavior for 2Br−/Br2 redox reaction. The anodic (11.2 mA cm−2) and cathodic (10.7 mA cm−2) peak current densities are higher for FG than that of other halogenated graphenes. ZBB flow cell fabricated with FG as bromine electrode exhibits enhanced electrochemical performance in terms of efficiency (81% of voltaic efficiency and 72% energy efficiency) and durability up to 350 cycles.

Enthalpic pairwise self-association of l-carnitine in aqueous solutions of some alkali halides at T = 298.15 K

Knowledge of the influence of ions of various nature on intermolecular hydrophilic and hydrophobic interactions in solutions is required in many research fields. In this paper, dilution enthalpies of zwitterion l-carnitine in aqueous NaCl, KCl and NaBr solutions of various molalities (b=0 to 3.0mol·kg−1) have been determined respectively at T=(298.15±0.01)K and p=(0.100±0.005)MPa by isothermal titration calorimetry (ITC). In light of the MacMillan–Mayer theory, the 2nd virial enthalpic coefficients (h2) have been calculated. The h2 coefficients increase gradually with increasing molality (b) of the three aqueous alkali halides solutions, from small negative values in pure water to relatively larger positive values in solution. The trends of h2 coefficients are ascribed to the salt effects on the balance between hydrophilic and hydrophobic interactions in pairwise self-associations. It is considered that the size of cations and anions exert influences on h2 coefficients through their surface charge densities and hydration (or dehydration) abilities.

Antimony porphyrins as red-light powered photocatalysts for solar fuel production from halide solutions in the presence of air.

Halide ions (X(-)) as cheap and abundant electron donors are oxidized with simulated sunlight in a photocatalytic reaction based on robust antimony porphyrins acting as red-light harvesting multielectron transfer sensitizers. Besides halogen formation (X2/X3(-)) this solar energy storing process under certain conditions also accumulates hydrogen peroxide (H2O2) as a second energy-rich compound.

Electrocatalytic Activation of Silver Nanowires‐modified Pt Electrode by Cyclic Voltammetry in Comparison with Differential Pulse Voltammetry in Halide Determination

AbstractCyclic voltammetric (CV) and differential pulse voltammetric (DPV) measurements were carried out to assess the changes in electrode reactivity in halide determination with a silver nanowire‐modified platinum electrode. With DPV, successive voltammograms of the halide solution revealed progressive deterioration of the oxidation currents corresponding to Br− and Cl−, while those of I− increased largely. Comparatively, CV is stable and effective to remove precipitates due to the reduction process, in which, the concentrated effect alleviated and the amount of AgI decreased. CV was consequently suggested to be favorable for halide determination, while playing a role in electrocatalytic activation of the electrode.

ChemInform Abstract: Three‐Component Coupling Reaction of Benzylic Halides, Carbon Dioxide, and N,N‐Dimethylformamide by Using Paired Electrolysis: Sacrificial Anode‐Free Efficient Electrochemical Carboxylation of Benzylic Halides.

Abstract Sacrificial anode-free efficient electrochemical carboxylation of benzylic halides was successfully performed by using a paired electrolysis protocol. Constant-current electrolysis of a DMF solution of benzylic halides in the presence of carbon dioxide using a one-compartment cell equipped with a Pt plate cathode and a Pt wire anode (quasi-divided cell) resulted in efficient three-component coupling reaction of benzylic halides, carbon dioxide and DMF to yield N-methyl-N-(phenylacetoxy)methylformamides, as carboxylated coupling products, in good yields.

“Anion-chromic” interactions of emeraldine base with hydroxide and halide anions in the solid polymer matrix

A behavior of polyaniline (PANI) composites with common polymers under different conditions is often a result of a synergetic combination of properties of their components. In this work we consider specificity of such a combination in terms of both hydrogen bonding of PANI with a matrix polymer poly(ethylene terephthalate) (PET) and its influence on interactions of the composite PANI–HCl/PET films or dedoped PANI/PET films with alkaline and alkali metal halide aqueous solutions. In particular, it is found that PANI in emeraldine base (EB) state forms a EB complex with hydroxide anions, which is confirmed not only by a strong blue shift of the exciton band in UV–vis spectra of both the dedoped PANI/PET (up to 529nm) and pure EB film (up to 579nm) but also by reversibility of this shift and its independence on the alkali cation nature. Additional confirmations of existence of this complex were obtained by quenching of the PL emission of EB by OH− anions in the dedoped PANI/PET and IR spectra of EB film after its interaction with the alkali solution. Formation of this EB–OH− complex is shown to be due to hydrogen bonding of hydroxide anions with amine groups of the dedoped PANI (EB) backbone. The EB–OH− complex is much more stable in the dedoped PANI/PET composite film than in the pure EB film probably due to additional hydrogen bonding of OH− anions with carbonyl oxygen atoms of the matrix. However, this complex in the PANI/PET film can be destroyed by dissolving in NMP or by contact with the solutions of alkali metal halides. Specifically, the complex instability in these solutions is enhanced in the halide anions range F−<Cl−<Br− that results in restoring the EB exciton band position and IR absorption bands of the pure EB.

Corrosion Behavior of ZK60 Magnesium Alloy in Sodium Halide Solutions

The corrosion behavior of ZK60 magnesium alloy in 3.5% sodium halides NaX (X =F, Cl, Br and I) solutions was studied by means of static immersion methods, potentiodynamic polar- ization measurement and SEM observation. The results showed that, the open circuit potential (OCP) of ZK60 alloy in 3.5% sodium halides solutions increased first and then became flat to a steady state. The corrosion behavior of ZK60 alloy was related to the halogen ions in the solutions: i.e. it was passivated in 3.5%NaF solution, while it was corroded in 3.5%NaCl, 3.5%NaBr and 3.5%NaI solutions and its corrosion rate decreased with immersion time, which may be ascribed to the formed protective corrosion products with the increasing pH value of the solutions.

Physico-chemical studies of a biologically active molecule (L-valine) predominant in aqueous alkali halide solutions with the manifestation of solvation consequences

The apparent molar volume (ϕV), viscosity B-coefficient and molar refraction (RM) have been determined of L-valine in aqueous solution of LiCl, NaCl and KCl at 298 K, 303 K and 308 K from density (ρ), viscosity (η) and refractive index (nD) measurements, respectively. The limiting apparent molar volumes (ϕV0) and experimental slopes (SV*) derived from the Masson equation have been interpreted in terms of solute–solvent and solute–solute interactions, respectively. The viscosity data were analysed using the Jones–Dole equation and the derived parameter B has also been interpreted in terms of solute–solvent interactions in the solutions. Molar refraction (RM) has been calculated using the Lorentz–Lorenz equation.

Cation Depth-Distribution at Alkali Halide Aqueous Solution Surfaces

Using synchrotron radiation Near-Ambient Pressure X-ray photoemission spectroscopy (NAP-XPS) in surface and bulk sensitive conditions, we specifically explored the depth distribution of Na+ ions near the vapor/liquid interface of saturated solutions of sodium halides (NaCl, NaBr, and NaI) kept at 278 K under a pressure of 8 mbar. By varying the photoelectron kinetic energy, and hence the probing depth, we show that the Na+ depth distribution near the surface is highly sensitive to the size and polarizability of the anion. The large polarizable anions, Br– and I– that segregate at the surface, tend to drag the Na+ ions closer to the liquid–water surface. However, this situation is not observed for the NaCl solution, in line with recent theoretical results.

Three-component coupling reaction of benzylic halides, carbon dioxide, and N,N-dimethylformamide by using paired electrolysis: sacrificial anode-free efficient electrochemical carboxylation of benzylic halides

Sacrificial anode-free efficient electrochemical carboxylation of benzylic halides was successfully performed by using a paired electrolysis protocol. Constant-current electrolysis of a DMF solution of benzylic halides in the presence of carbon dioxide using a one-compartment cell equipped with a Pt plate cathode and a Pt wire anode (quasi-divided cell) resulted in efficient three-component coupling reaction of benzylic halides, carbon dioxide and DMF to yield N-methyl-N-(phenylacetoxy)methylformamides, as carboxylated coupling products, in good yields.

Development and application of in situ/operando soft X-ray transmission cells to aqueous solutions and catalytic and electrochemical reactions

In this review, we have demonstrated several applications of newly-developed in situ/operando liquid flow cells for the transmission XAS (X-ray absorption spectroscopy) measurement in the soft X-ray undulator beamline BL3U dedicated to the chemical application of UVSOR-III Synchrotron. The liquid layer is sandwiched between two thin membranes and its thickness is easily controllable to optimize the absorbance. Liquid samples are exchangeable in situ. Molecular spectra in liquid and gas phases are simultaneously measureable and it makes the energy calibration rather easy. By using a standard version of the liquid cells, we have investigated local structures of several aqueous solutions of alkali halides, methanol, pyridine, and acetonitrile. To observe catalytic and electrochemical reactions under realistic conditions, we have developed in situ/operando versions of the liquid cells. We have investigated local structures of the catalytic hydration reaction of cyanopyrazine under the temperature control and the electrochemical reaction of aqueous iron sulfate solutions using the built-in electrodes under the same scan rate as in cyclic voltammetry. We have discussed future perspectives of our in situ/operando liquid flow cells applied to XAS in the soft X-ray region.

Transforming Hybrid Organic Inorganic Perovskites by Rapid Halide Exchange

We report on rapid halide exchange in metal halide perovskite of the general formula MAPbX3 (X = Cl, Br, or I). We find that when the perovskite is infiltrated in a mesoscopic scaffold, halide substitution on the perovskite lattice is strikingly fast, being completed within seconds or minutes after contact with the halide solution. An exception is the exchange of bromide by iodide, which is slower and incomplete. Halide substitution occurs rapidly even for planar perovskite films which are several tens of nanometers thick. However, with thicker films the reaction requires hours, showing that the mesoscale greatly accelerates the halide exchange process. The time course of the substitution reactions has been monitored by in situ photoluminescence, absorption spectroscopy, and X-ray diffraction measurements. We show that the halide exchange can be a powerful tool to effect perovskite transformations.