Potassium Fluoride Solutions Research Articles

Pseudocapacitance of Bimetallic Solid‐Solution MXene for Supercapacitors with Enhanced Electrochemical Energy Storage

AbstractMXenes, a family of 2D transition metal carbides, are considered promising high‐rate pseudocapacitive materials because of their metallic‐like conductivity and transition metal oxide‐like surfaces. Currently, nearly 50 stoichiometric MXenes have been synthesized. However, only a few MXenes, such as Ti3C2, have shown stable pseudocapacitive charge storage so far. Further improving the inherent pseudocapacitance of MXenes without losing their cyclability remains a challenge. Herein, a mild method is reported to produce highly stable bimetallic solid‐solution MXene Ti2VC2 using a solution of potassium fluoride and hydrochloric acid. The electrochemical properties of resulting multilayered clay‐like and delaminated Ti2VC2 films are investigated, exceeding the performance of typical Ti3C2 in acidic electrolytes. These electrodes deliver up to 2000 F cm−3 and retain more than 90% of their initial capacitance after 20 000 cycles, surpassing most state‐of‐the‐art supercapacitor materials known. The pseudocapacitive charge storage of Ti2VC2 is deeply investigated through in situ and ex situ experimental studies, confirmed the pseudocapacitive mechanism is a combination of hydrated H+ intercalation and surface redox. This work provides a practical route toward future rational design on the atomic scale for high‐performance pseudocapacitive materials.

Postmortem reference concentrations of 68 elements in blood and urine.

Fatal intoxications, both accidental and intentional, are a global issue. In the Western world, intoxications with pharmaceuticals dominate, but in other parts of the world, other substances are more common. In a forensic setting, elemental intoxications are of great importance when investigating both accidental, suicidal, and homicidal deaths. The current study presents normal postmortem reference concentrations of 68 elements in femoral blood and urine. In addition, possible sources of error such as contamination from sample tubes, preservative potassium fluoride (KF) solution, and storage time are evaluated. Paired femoral blood and urine samples from 120 cases of death by suicidal hanging in Sweden were collected. Additionally, multiple batches of sample tubes and multiple batches of KF solution were also analyzed. Concentrations of elements were determined by double focusing sector field ICP-MS. Key descriptive statistics for 68 elements are provided in blood and urine. Contamination from sample tubes was minor compared to the overall mean elemental concentrations in both blood and urine. KF solution contained a large assortment of elements, but the overall contribution is relatively minor for most elements given the small amounts of solution added to samples. There were significant differences for 22 elements in blood and 17 elements in urine between samples with short and long storage time. The present study provides an important tool when evaluating postmortem elemental concentrations. It fills a needed gap between large antemortem population studies and postmortem case reports or small case series of elemental intoxications.

Postmortem reference concentrations of elements in blood and urine

To establish postmortem reference concentrations of elements. Fatal intoxications, both accidental and intentional, are a global issue. In the western world intoxications with pharmaceuticals dominate, but in other parts of the world other substances are more common. Intoxication with elemental compounds is generally considered to be uncommon. In a forensic setting, elemental intoxications are of great importance when investigating both accidental, suicidal, and homicidal deaths. Arsenic, for example, is a classical poison which also has relevance in the modern era. Unlike for pharmaceuticals, postmortem reference concentrations for elements are scarce. For many elements it is therefore unknown if, and to what extent, they are affected by postmortem redistribution. The current study presents normal postmortem reference concentrations of 68 elements in femoral blood and urine. In addition, possible sources of error such as contamination from collection tubes, preservative potassium fluoride solution and storage time are evaluated. Paired blood and urine samples from 120 cases of death by suicidal hanging in Sweden were collected. 20 cases from each of the six local units of forensic medicine were used to account for possible regional differences. Additionally, the included cases reflected both short and long storage times. To account for possible elemental contamination from collection tubes and the added potassium fluoride solution, multiple batches of tubes and multiple samples of potassium fluoride solution were also analysed. Concentrations of elements were determined by double focusing sector field ICP-MS. Key descriptive statistics for all 68 elements are provided (including mean, median and percentiles) in blood and urine. Forensic highlights include blood concentrations of total arsenic (mean: 4.25 μg/g), thallium (mean: 0.14 μg/g) and antimony (mean: 14.82 μg/g). For several elements in blood and urine ( n = 24 and n = 25, respectively) a majority of elemental concentrations were below the limit of detection. The contribution of contamination from collection tubes were minor compared to the overall mean elemental concentrations in both blood and urine. Though the added solution of potassium fluoride contained a large assortment of elements, given the small amounts of this solution added to samples, the overall contribution is minor for most elements relative to the overall mean. However, there was a significant difference between samples with short and long storage time for 22 elements in blood and 17 elements in urine. These differences reflected both increases and decreases in concentration. Relative to antemortem elemental concentrations the postmortem concentrations show both increases and decreases. Of special note are markedly higher concentrations for several elements in blood (such as cadmium, chromium, manganese and antimony) compared to several antemortem populations. In general, it can be assumed the phenomenon of postmortem redistribution is as large for elements as it is for drugs and other substances. When evaluating individual concentrations, it is important to be aware of potential sources of contamination and the potential influence of storage time. Concentrations indicating overexposure must be evaluated together with autopsy findings and case circumstances to form a holistic view of the case as a whole. The present study provides an important tool when evaluating postmortem elemental concentrations. It fills a needed gap between large antemortem population studies and postmortem case reports or small case series of elemental intoxications. Together with the forensic autopsy and circumstantial information the present references will aid in diagnosing cases of potential elemental overexposure.

Synthesis of KZnF\(_{3}\) Phosphors by Co-Precipitation Method

Synthesis of KZnF\({}_{3}\) is rather tedious. Typical problems of fluoride synthesis are faced with more acuteness. Even in wet chemical preparations, use of hygroscopic starting materials like zinc chloride or nitrate presents considerable difficulties. A simple precipitation synthesis of KZnF\({}_{3}\) with aqueous solutions of zinc sulfate and potassium fluoride is described. Precipitation at the room temperature produces the compound profoundly contaminated with hydroxide phase. Phase pure compound is obtained when boiling solutions are mixed. Activators Cerium and europium could be incorporated by adding the corresponding sulfates to zinc sulfate solution during the precipitation. As prepared phosphor exhibited typical Ce\({}^{3+}\) luminescence. For obtaining Eu\({}^{2+}\) luminescence, the phosphor had to be given reducing treatment.

Fluoride effect indicators in Phaseolus vulgaris seeds and seedlings.

BackgroundFluoride (F) is one of the main environmental pollutants, and high concentrations are commonly detected in the air and in both surface and groundwater. However, the effects of this pollutant on seed germination and on the initial growth of crop seedlings are still poorly understood. In this context, the aim of this study was to assess morphoanatomical, physiological and biochemical fluoride effect indicators in Phaseolus vulgaris L. seeds and seedlings.MethodsP. vulgaris seeds were exposed to a liquid potassium fluoride solution (KF, pH 6.0) at concentrations of 0 (control), 10, 20, 30 mg L−1 for 7 days. A completely randomized experimental design was applied, consisting of four treatments with four replications each. During the experimental period, physiological (7 days) anatomical and histochemical (2 days), biochemical and chemical (4 days) assessments. An analysis of variance was performed followed by Dunnett’s test. to determine significant differences between the KF-exposed groups and control seeds; and a multivariate analysis was performed.ResultsThe germination parameters, and anatomical, morphological, physiological, biochemical and nutritional characteristics of the seedlings did not show negative effects from exposure to KF at the lowest doses evaluated. On the other hand, treatment with the highest dose of KF (30 mg L−1) resulted in a lower germination rate index and increase in abnormal seedlings, and higher electrical conductivity. A lower root length, magnesium content and photochemical efficiency were also observed. The exposure of P. vulgaris to KF, regardless the dose did not affect seeds anatomy and the accumulation of starch and proteins, in relation to the control group.ConclusionsOur findings demonstrated that P. vulgaris seedlings were tolerant to KF solutions up to 20 mg L−1, and sensitive when exposed to 30 mg KF L−1.

Transformation of calcite CaCO3 to fluorite CaF2 by action of KF solution

Conversion of microcrystalline calcium carbonate powder to fluorite by reacting it with potassium fluoride solution is studied. The reaction occurs at room temperature and yields a white flowing powder. Rhombohedral CaCO3 microcrystals are replaced by an ensemble of CaF2 nanoparticles sized ca. 20 nm, which in part fill in the volume of the precursor microcrystals. The product calcium fluoride contains about 2 mol% KF. KCaF3 is not produced by the reaction, and KCaF3 is a high-temperature compound stable above 500 оС.

Transformation of Calcite CaCO3 to Fluorite CaF2 by Action of KF Solution

Conversion of microcrystalline calcium carbonate powder to fluorite by reacting it with potassium fluoride solution is studied. The reaction occurs at room temperature and yields a white flowing powder. Rhombohedral CaCO 3 microcrystals are replaced by an ensemble of CaF 2 nanoparticles sized ca. 20 nm, which in part fill in the volume of the precursor microcrystals. The product calcium fluoride contains about 2 mol % KF. KCaF 3 is not produced by the reaction, and KCaF 3 is a high-temperature compound stable above 500 о С.

Potassium-induced partial inhibition of lactoperoxidase: structure of the complex of lactoperoxidase with potassium ion at 2.20Å resolution.

Lactoperoxidase, a heme-containing glycoprotein, catalyzes the oxidation of thiocyanate by hydrogen peroxide into hypothiocyanite which acts as an antibacterial agent. The prosthetic heme moiety is attached to the protein through two ester linkages via Glu258 and Asp108. In lactoperoxidase, the substrate-binding site is formed on the distal heme side. To study the effect of physiologically important potassium ion on the structure and function of lactoperoxidase, the fresh protein samples were isolated from yak (Bos grunniens) colostrum and purified to homogeneity. The biochemical studies with potassium fluoride showed a significant reduction in the catalytic activity. Lactoperoxidase was crystallized using 200mM ammonium nitrate and 20% PEG-3350 at pH 6.0. The crystals of LPO were soaked in the solution of potassium fluoride and used for the X-ray intensity data collection. Structure determination at 2.20Å resolution revealed the presence of a potassium ion in the distal heme cavity. Structure determination further revealed that the propionic chain attached to pyrrole ring C of the heme moiety, was disordered into two components each having an occupancy of 0.5. One component occupied a position similar to the normally observed position of propionic chain while the second component was found in the distal heme cavity. The potassium ion in the distal heme cavity formed five coordinate bonds with two oxygen atoms of propionic moiety, Nε2 atom of His109 and two oxygen atoms of water molecules. The presence of potassium ion in the distal heme cavity hampered the catalytic activity of lactoperoxidase.

Polyimide nanohybrid films with electrochemically functionalized graphene

AbstractGraphite was functionalized electrochemically in a potassium fluoride solution and used to prepare polyimide (PI)/graphene nanohybrid films. The as‐made electrochemically fluorinated graphene (EFG) was used to prepare nanohybrid films with colorless PI, which was synthesized from 4,4′‐(hexafluoroisopropylidene) diphthalic anhydride and bis(trifluoromethyl) benzidine by in situ polymerization. The surface functionalization of graphite was characterized by powder XRD, TEM with energy dispersive X‐ray spectroscopy elemental mapping, X‐ray photoelectron spectroscopy, Raman spectroscopy, and TGA. The microstructure of the films was characterized by Fourier transform IR spectroscopy, XRD and SEM. The film properties were measured using a universal testing machine, TGA, dynamic mechanical analysis, four‐point probe, UV–visible spectroscopy and water contact angle analysis. EFG improved the tensile strength and modulus of the nanohybrid films by 20% and 50%, respectively. The glass transition temperature and electrical conductivity of the nanohybrid films were 12 °C and nine orders of magnitude higher than those of the neat PI film, respectively. The nanohybrid film maintained 80% optical transmittance even after the addition of 0.1 wt% EFG. © 2019 Society of Chemical Industry

Fabrication and device characterization of potassium fluoride solution treated CZTSSe solar cell

Post deposition treatment (PDT) for Cu2ZnSn(S,Se)4 (CZTSSe) was carried out by simply dipping the absorber into the KF solution at 80 °C. The dipping time of absorber in KF solution was found to be crucial to device parameters of CZTSSe solar cell. The K-doping improved the solar cell efficiency from 4.4% to 7.6% by 1 min dipping whereas the longer than 5 min dipping solar cells showed distorted kink J-V curves. The activation energy of CZTSSe solar cell was increased upto 1 min KF treatment from 0.83 eV to 0.92 eV which indicates interface recombination is reduced significantly. However, the activation energies of 5 min and 10 min dipping solar cells were found to be 0.81 eV and 0.63 eV where dominant recombination was interface recombination. Furthermore, trap energies of 49 meV and 298 meV of pristine CZTSSe solar cell were modified to 33 meV and 117 meV for 1 min treated CZTSSe solar cell. Trap energies of 5 min were calculated to be 112 meV and 147 meV. The proper KF doping passivated the shallow as well as deep defects of CZTSSe solar cell which is reflected in photovoltaic performances directly.

Simultaneous determination of selected eicosanoids by reversed-phase HPLC method using fluorescence detection and application to rat and human plasma, and rat heart and kidney samples

Eicosanoids are biologically active lipid-derived oxidative metabolites of arachidonic acid. We, herein, present an improved sensitive, selective and robust high performance liquid chromatography (HPLC)-fluorescence assay for simultaneous quantification of eicosanoids in human plasma and rat tissues. Aliquots of 200μL of plasma or 30mg of heart or kidney tissues were spiked with 16-hydroxydecanoic acid as internal standard, and extracted with anhydrous acetonitrile using solid phase cartridges. The eluted samples were dried, reconstituted in anhydrous acetonitrile and labeled with 2-(2,3-naphthalimino)ethyl-trifluoromethanesulphonate in the presence of saturated potassium fluoride solution in anhydrous acetonitrile and N,N-diiospropylethylamine as catalyst. The derivatized eicosanoids were extracted with anhydrous acetonitrile using solid phase cartridges. Chromatographic separation was achieved on a C18 reversed phase column using gradient mobile phase of 0.05% of formic acid:acetonitrile:water at 0.8mL/min flow rate. The analytes were detected at excitation and emission wavelength of 260 and 396nm, respectively. The assay was linear (r2≥0.98) in the concentration range of 0.01–2.5μg/mL. The intra-day and inter-day coefficients variation was less than 19.8%. Using this assay, we were able to quantify arachidonic acid metabolites simultaneously in human and rat biological samples.

Do ions affect the structure of water? The case of potassium halides

We study the structural properties of aqueous solutions of potassium chloride and fluoride at ambient conditions and upon supercooling with the use of molecular dynamics. We perform the calculations at increasing concentration in a range from 0.67mol/kg up to 3.96mol/kg. We investigate the modifications of the hydration shells and the changes in the water structure induced by the presence of the ions. The oxygen–oxygen structure is strongly dependent on the ionic concentration while the hydrogen bonding is well preserved. The results show that increasing the ion concentration is analogous to increase pressure on pure water. The KF salt has a stronger effect on water due to the fluoride anion. F− appears also more effective as substitutional of the oxygen in the water network with possible relevant consequences on the tendency of water to transform to the high density phase.

Solubility of potassium fluoride in aqueous solution at different temperatures 298.15K–353.15K

In this investigation, the binary aqueous solutions of Potassium Fluoride have been studied using the hygrometric method at different temperatures 298.15K–353.15K. The water activities are measured at molalities from 0.10 mol kg −1 to saturation. The obtained data allow the deduction of osmotic coefficients. From these measurements, the ionic parameters are determined and used to predict the solute activity coefficients. Thermodynamic characteristics, solubility products K° sp and the standard molar Gibbs energy of dissolution ΔG° diss are given. The predicted solubility isotherms are compared with the literature data.

Thermodynamic Analysis of Homologous α-Amino Acids in Aqueous Potassium Fluoride Solutions at Different Temperatures

Partial molal volumes (\(V_{\phi} ^{0}\)) and partial molal compressibilities (\(K_{\phi} ^{0}\)) for glycine, L-alanine, L-valine and L-leucine in aqueous potassium fluoride solutions (0.1 to 0.5 mol⋅kg−1) have been measured at T=(303.15,308.15,313.15 and 318.15) K from precise density and ultrasonic speed measurements. Using these data, Hepler coefficients (\(\partial^{2}V_{\phi} ^{0}/\partial T^{2}\)), transfer volumes (\(\Delta V_{\phi} ^{0}\)), transfer compressibilities (\(\Delta K_{\phi} ^{0}\)) and hydration number (nH) have been calculated. Pair and triplet interaction coefficients have been obtained from the transfer parameters. The values of \(V_{\phi} ^{0}\) and \(K_{\phi} ^{0}\) vary linearly with increasing number of carbon atoms in the alkyl chain of the amino acids. The contributions of charged end groups (\(\mathrm{NH}_{3}^{+}\), COO−), CH2 group and other alkyl chains of the amino acids have also been estimated. The results are discussed in terms of the solute–cosolute interactions and the dehydration effect of potassium fluoride on the amino acids.

Reactions of Sodium Peroxide with Components of Legacy Plutonium Materials

Plutonium oxide (PuO2) calcined at >900 °C resists dissolution in nitric acid (HNO3)-potassium fluoride (KF) solutions commonly used for their dissolution. The Savannah River National Laboratory (SRNL) has developed an alternate method for large samples of PuO2-bearing materials using sodium peroxide (Na2O2) fusion as a pretreatment. The products of the reaction between Na2O2 and PuO2 have been reported in the literature. As part of the SRNL development effort, additional data about the reaction between Na2O2 and PuO2 were required. Also needed were data concerning the reaction of Na2O2 with other components that may be present in the feed materials. Sodium peroxide was reacted with aluminum metal (Al), beryllium metal (Be), graphite, potassium chloride (KCl), magnesium chloride (MgCl2), and calcium chloride (CaCl2). The paper reports and discusses the reaction products of these and related compounds with Na2O2.

EFFECT OF IONIC SIZES OF HALIDE ANIONS OF POTASSIUM SALTS ON SURFACE AND INTERFACIAL TENSIONS OF BENZENE AND WATER INTERFACES FOR MUTUAL MIXING

Surface tension (γ, mN/m) of potassium halide salts with water and interfacial tension (IFT) (±0.01 mN/m) of benzene interfaces with water are reported at 298.15 K temperature. The 0.1, 0.5 and 1.0 mol kg-1 potassium fluoride ( KF ), chloride ( KCl ), bromide ( KBr ) and potassium iodide ( KI ) solutions were studied. The KCl, KBr, KF and KI increased the surface tension by 5.2, 4.0, 3.1 and 3.0%, respectively, with salt–water interaction influence by anionic sizes. The surface tension of water from air–water to benzene–water interfaces is decreased by 51% due to the benzene–water mutual interaction with dipolar and π-conjugation. The KI, KF, KCl and KBr salts decrease the IFT by 63, 61, 61 and 56%, respectively, because of larger differences in sizes of the anions and the K + with individual salt. The KI developed stronger interactions with an induced potential of a large sized I - anion that held the water engaged and integrated the aqueous phase with higher interfacial tension. The dipolar and π-conjugation interaction model is proposed with biphasic systems.

Relation between Surface Tension and Ion Adsorption at the Air−Water Interface: A Molecular Dynamics Simulation Study

Classical molecular dynamics simulations of aqueous solutions of sodium chloride and potassium fluoride at two different concentrations have been carried out using polarizable force fields and standard additive force fields (not including polarizability explicitly). We show that the presence of chloride ions at the air-solution interface, as predicted from the polarizable simulations of NaCl solutions, is reconcilable with the classical thermodynamics results of Gibbs absorption theory. We discuss the role of system size in the establishment of a bulklike region in which the ion densities have converged to the same value. We compare the results for NaCl solutions with those obtained for KF at two concentrations. We find that the computed surface tension and the surface excess follow the experimental trend for each salt solution. We have characterized the extent of adsorption by calculating the fraction of the solution surface area that is occupied by each ion. The analysis reveals that, as expected, in the KF solution neither the cation nor the anion is present on the surface, regardless of whether or not a polarizable force field is employed. On the other hand, in the NaCl solutions, chloride anions occupy the surface to an extent that is roughly proportional to their bulk concentration, but only when a polarizable model is used.

Kinetics and mechanism of gallium discharge and ionization in an alkaline solution of potassium fluoride

Mechanism of gallium discharge and ionization on a liquid gallium electrode in a fluoride-alkaline electrolyte was studied. The exchange currents, transfer coefficients in the cathodic and anodic processes, and the activation energy of the electrode process were determined. The conditions in which gallium(I) ion-intermediates are formed were analyzed. The coordination numbers of the gallium complexes formed in alkaline fluoride solutions were calculated.

Fluoride released from glass-ionomer cement is responsible to inhibit the acid production of caries-related oral streptococci

Objectives Glass-ionomer cements (GICs) are known to have inhibitory effects on bacterial growth, but the biochemical mechanism of this property has not been fully understood. This study aimed to evaluate inhibitory effects of GIC on the acid production of caries-related oral streptococci, and to identify the components responsible for the inhibition. Methods An eluate was prepared by immersing set GIC in phosphate-buffered saline at 37 °C for 24 h. Fluoride and other elements in the eluate were quantified by fluoride ion electrode and atomic absorption photometry, respectively. Streptococcus mutans NCTC 10449 and Streptococcus sanguinis NCTC 10556 were used to evaluate the pH fall and the rate of acid production after the addition of glucose in the presence or absence of the eluate. Acidic end products from glucose were also assayed by carboxylic acid analyzer. Results The eluate contained silicon (1.24 ± 0.26 mM), fluoride (0.49 ± 0.02 mM) and aluminum (0.06 ± 0.00 mM), and inhibited the pH fall and the acid production rate of both streptococci at acidic pH, with a concomitant decrease in lactic acid production. These effects were comparable to those of a potassium fluoride solution containing the same concentration of fluoride as the eluate. Significance These results indicate that the GIC eluate inhibits the acid production of caries-related oral streptococci at acidic pH and that the effect is due to fluoride derived from the GIC. Thus, adjacent to GIC fillings, bacterial acid production and the subsequent bacterial growth may decrease, establishing a cariostatic environment.

Zinc oxide hollow microstructures and nanostructures formed under hydrothermal conditions

Zinc oxide low-dimensional hollow structures in the form of hexagonal plates with holes at the center of the {0001} facets are synthesized in the course of the low-temperature interaction of ZnO precursors with aqueous solutions of potassium fluoride under hydrothermal conditions. Crystals have the shape of single-walled or multiwalled “nuts.” The high optical quality of the structures is confirmed by cathodoluminescence data at room temperature. The mechanism of the formation of ZnO “nanonuts” and products of the interaction of the ZnO precursors with KF is proposed.