Salts In Aqueous Media Research Articles

Sulfonylation of Pyridyl Phosphonium Salts with Sulfinate Salts in Aqueous Media for the Synthesis of 4-Pyridyl Sulfones via C-P Bond Cleavage.

A Na2S2O8-initiated sulfonylation of pyridyl phosphonium salts with sulfinate salts in aqueous media has been developed for facile access to 4-pyridyl sulfones. The reactions, which employed pyridyl phosphonium salts as efficient pyridylation agents via C-P bond activation, showed both broad substrate generality and good functional group compatibility. In addition, the scale-up synthesis and the late-stage modification of pharmaceutically active complex molecules (e.g., loratadine, bisacodyl) could also be successfully realized.

Fluorescence lifetime of pyrene butyric acid as a versatile sensing tool for monitoring self-assembled systems and microenvironment

Sensing applicability of the fluorescence lifetime of pyrene butyric acid (PBA) to understand the aggregation behaviour and microheterogeneity of different charged self-assembled surfactants i.e., anionic (sodium dodecyl sulfate, ∼ 8.5 mM), cationic (Cetyltrimethylammonium bromide, ∼ 0.95 mM), and non-ionic (Triton X100, ∼ 0.27 mM) in aqueous solution is explored in this study. Time domain fluorescence decay of PBA is introduced for the first time as a sensitive tool for characterizing the molecular microenvironment and for predicting the aggregation behaviour of surfactants, including the monitoring low to higher-order aggregates. A non-extensive distribution analysis on the fluorescence decay profiles yields the fluorescence lifetime and Full Width at Half Maxima (FWHM), with the latter serving as an indicator of the heterogeneity of the molecular microenvironment of the 'fluoroprobe'.The analytical strength of the fluorescence lifetime of PBA as a sensing tool has been validated using biosurfactants sodium cholate (NaC) and sodium deoxycholate (NaDC) with high fidelity. Careful analysis of the non-extensive distribution of the lifetime of PBA displays a substantial sensitivity towards microheterogeneity in its immediate vicinity and hence monitors the higher-order aggregation behaviour of bile salts in aqueous medium.

Tuning Pd-to-Ag Ratio to Enhance the Synergistic Activity of Fly Ash-Supported PdxAgy Bimetallic Nanoparticles.

Fly ash (FA)-supported bimetallic nanoparticles (PdxAgy/FA) with varying Pd:Ag ratios were prepared by coprecipitation of Pd and Ag involving in situ reduction of Pd(II) and Ag(I) salts in aqueous medium. All the supported nanoparticles were thoroughly characterized with the aid of powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), electron microscopy (field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM)), and elemental analyses, which include inductively coupled plasma-optical emission spectroscopy (ICP-OES) and energy-dispersive X-ray spectroscopy (EDS). A gradual broadening and shifting of PXRD peaks, ascribable to Ag, to higher angles with an increase in the Pd:Ag ratio affirms the alloying of interface between Pd and Ag nanoparticles. The coexistence of Pd and Ag was further confirmed by EDS elemental mapping as well as by the presence of bimetallic lattices on the FA surface, as evident from the high-resolution TEM analysis. The dependency of crystallite size and average size of bimetallic nanoparticles on Ag loading (mol %) was elucidated with the help of a combination of PXRD and TEM studies. Based on XPS analysis, the charge transfer phenomenon between contacting Pd-Ag sites could be evident from the shifting of 3d core electron binding energy for both Pd and Ag compared with monometallic Pd and Ag nanoparticles. Following a pseudo-first-order reaction kinetics, all the nanocatalysts were able to efficiently reduce 4-nitrophenol into 4-aminophenol in aqueous NaBH4. The superior catalytic performance of the bimetallic nanocatalysts (PdxAgy/FA) over their monometallic (Pd100/FA and Ag100/FA) analogues has been demonstrated. Moreover, the tunable synergistic effect of the bimetallic systems has been explored in detail by varying the Pd:Ag mol ratio in a systematic manner which in turn allowed us to achieve an optimum reaction rate (k = 1.050 min-1) for the nitrophenol reduction using a Pd25Ag75/FA system. Most importantly, all the bimetallic nanocatalysts explored here exhibited excellent normalized rate constants (K ≈ 6000-15,000 min-1 mmol-1) compared with other supported bimetallic Pd-Ag nanocatalysts reported in the literature.

Clouding of TX-100 and promethazine hydrochloride mixture: Impacts of Na salts on the physicochemical parameters and interaction forces linked with studied components

Interest in the phase separation behaviors and interactions between non-ionic surfactants and various drug species in aqueous salt solutions have grown significantly in recent years due to their extensive applications in industry and medicine. This study explored the clouding characteristics of a triton X-100 (TX-100) and promethazine hydrochloride (PMH) mixture in various aqueous sodium salt (such as NaOAc, NaOxal, Na2CO3, NaHCO3, and NaNO3) solutions. The physicochemical variables and interaction forces between TX-100 and PMH species in different sodium salt media were successfully determined by measuring the cloud point (CP). Different electrolyte solutions have been found to alter the clouding behavior of TX-100 + PMH. The CP magnitudes for TX-100 + PMH combinations decreased as the Na salt concentrations were increased, and the respective CPs decreased in the order: Na2CO3 > NaOxal > NaHCO3 > NaOAc > NaNO3. The salting-out effect played a significant role in decreased CP, possibly due to the reduction in water solubility of solutes in the presence of other soluble ions within the mixtures. The ΔGc0 of TX-100 and the employed drug mixture in aqueous salt media was positive, demonstrating the non-spontaneous nature of the clouding process. However, the non-spontaneity of phase separation in the corresponding mixtures decreased as the electrolyte content of the solution increased. The ΔHc0 and ΔSc0 were negative, suggesting that the clouding progression in the studied mixtures was exothermic and driven by enthalpy change. The evaluation of the intrinsic enthalpy gain (ΔHco,∗) and the compensation temperature (Tc) provided evidence of the interactions between TX-100 and PMH species. This research is significant and may be useful in different industries, including for formulating various drugs in the pharmaceutical industry.

Size-Dependent Protein Adsorption on a Nanoparticle.

This study presents the mechanism of adsorption of a model protein within an electrical double layer (EDL) of a charged silica NP in an aqueous salt medium. In contrast to previous works, the charge regulation model analyzes the surface chemistry and electrostatic charge within the EDL by considering polarization, morphology, topography, and protonation/deprotonation. This model is coupled with the three protein adsorption models, such as Classical Langmuir (CLM), Extended Langmuir (ELM), and Two-State (TSM). By this means, surface curvature, conformational changes, and size- and pH-dependent characteristics of protein adsorption are allowed to be observed together in the present numerical model. For a parametric investigation, ionic concentration and pH of the solution, surface charge density, initial protein concentration, electrostatic charge of the protein, and the diameter of the NP are varied systematically. The validation studies with the experimental data agree well with the literature. The size-dependent protein adsorption is simulated and revealed with the current numerical model. Space charge density, chemistry, and morphology of NP's surface profoundly influence adsorption characteristics.

Deoxyfluorination of Electron-Deficient Phenols.

In this study, we report a facile synthesis of 2-chloro-1,3-bis(2,6-diisopropylphenyl)imidazolium salts in aqueous media under ambient conditions using hypochlorite as a chlorinating agent. In addition, an air-stable and moisture-insensitive deoxyfluorination reagent based on poly[hydrogen fluoride] salt is presented, which is capable of converting electron-deficient phenols or aryl silyl ethers into the corresponding aryl fluorides in the presence of DBU as a base, with good to excellent yields and high tolerance to functional groups.

Metal-supported cathodically activated graphite via self-reduction as electrocatalysts for efficient hydrogen evolution reaction

Surface modification is a promising approach to modulate the electrocatalyst properties for their further use in energy storage and conversion. In this work, electrochemical-based approach was proposed to generate metallic particles-supported graphite rod (GR). The approach is based on the cathodic activation of GR in the presence of alkali metal salts in dry organic solvent. The activated GR possess a high reducing power that was successfully employed to spontaneously reduce metallic salts in aqueous media. The surface analyses confirm the formation of metallic nanoparticles supported GR. Interestingly, the metallic nanoparticles were found to be generated onto and intercalated into the GR. Next, the generated materials were used as electrocatalyst to drive the hydrogen evolution reaction. Our results demonstrate that the electrocatalytic performances depend on various parameters including the radius of the alkali metal cation and the injected charge during the electrochemical activation. The as-prepared Pt/Li-GR exhibits the best electrochemical activity and stability toward the hydrogen evolution reaction. The necessary overpotential value to reach a current density of 10 mA cm−2 is 40 mV for the Pt/Li-GR, and almost negligible overpotential change is observed during the stability tests. In addition, the proposed approach was successfully used to generate Pd/Li-GR catalyst. More impressively, the latter displays higher HER performances when compared to other reported Pd-based catalysts and comparable performance with commercial Pt/C catalyst.

Toward a Selective Analysis of Heavy Metal Salts in Aqueous Media with a Fluorescent Probe Array.

Detection of heavy meals in aqueous media challenges worldwide research in developing particularly fast and affordable methods. Fluorescent sensors look to be an appropriate instrument for such a task, as recently they have been found to have made large progress in the detection of chemical analytes, primarily in the environment, along with biological fluids, which still suffer from not enough selectivity. In this work, we propose a new fluorescent method to selectively recognize heavy metals in an aqueous solution via employing an array of several fluorescent probes: acridine yellow, eosin, and methylene blue, which were taken as examples, being sensitive to a microsurrounding of the probe molecules. The exemplary sensor array generated six channels of spectral information through the use of various combinations of excitation and detection wavelengths. Following the known multisensor approach, we applied a linear discriminant analysis to selectively distinguish the vector signals from the sensor array from salts of heavy metals—Cu, Pb, Zn, Cd, and Cz—at the concentration ranges of 2.41 × 10−6–1.07 × 10−5 M, 2.8 × 10−5–5.87 × 10−4 M, 1.46 × 10−6–6.46 × 10−6 M, 1.17 × 10−8–5.2 × 10−8 M, and 2.11 × 10−6–9.33 × 10−6 M, respectively. The suggested approach was found to be promising due to it employing only one cuvette containing the test solution, simplifying a sample preparation when compared to preparing a variety of solutions in tests with single fluorescence probes.

Effect of ionic liquid on the micellization behavior of bile salts in aqueous medium

Interfacial and aggregation behavior of sodium cholate (NaC) and sodium deoxycholate (NaDC) in aqueous ionic liquid (IL, 1-butyl-3-methylimidazolium tetrafluoroborate) medium were investigated. Studies were also carried out in the presence of NaBF4. Both IL and NaBF4 reduce the critical micelle concentration (CMC) of bile salts, determined by surface tension, conductance, and fluorescence spectroscopic techniques; effect of NaBF4 is more prominent than IL. CMC of NaC was higher than NaDC because of its higher hydrophilicity. IL, in addition to its salt-like behavior, results in associative interaction with the bile salts. Surface excess (Гmax), surface pressure at the CMC (πCMC) were evaluated from surface tension data. Гmax and πCMC values gradually decreased with increasing the IL and NaBF4 concentration. Negative Gibbs free energy change for micellization (ΔG 0 mic) and interfacial adsorption (ΔG 0 ads) indicate spontaneity of micellization and interfacial adsorption, however to different magnitude. Fraction of counter ion dissociation, evaluated from conductance data, systematically decreased with increasing IL and NaBF4 concentration. Aggregation number, determined by fluorescence quenching method, increased with increasing IL and NaBF4 concentration that are in consonance with the size of the aggregates, determined by dynamic light scattering study. IL induced the formation of larger facial aggregates by bile salts; the effect was more imperative in case of NaDC than NaC. In case of NaBF4 the opposite trend was recorded. Such systems are considered to have potential application where the dual benefit of both a surfactant and an IL are warranted.

Isolation, characterization and semi-synthesis of natural products dimeric amide alkaloids

Isolation, characterization and semi-synthesis of natural products dimeric amide alkaloids

Mesoporous additive-free vaterite CaCO3 crystals of untypical sizes: From submicron to Giant

Mesoporous CaCO3 crystals of sizes in the range 3–15 μm have attracted significant scientific attention as fully decomposable biocompatible drug delivery vectors. They are also used as sacrificial templates to produce polymer-based microcarriers (capsules, beads) and polymer scaffolds for tissue engineering at biologically friendly conditions. However, fabrication of CaCO3 crystals with the sizes beyond the conventional range without additives is still a challenge. There is a desperate need of sub-micrometre and sub-millimetre biocompatible and easily decomposable vectors for intracellular delivery and design of tailor-made polymer scaffolds, respectively. In this study, additive-free one-step fabrication of vaterite mesoporous crystals with sizes in the range from submicron (0.72 μm) up to tens of microns (55 μm) sizes is proposed. Crystals are grown by mixing of Ca2+ and CO32− salts in aqueous media. Internal structure and morphology of the crystals have been investigated. Encapsulation of lysozyme by means of co-synthesis shows an enhanced entrapment into submicron crystals. Besides, the approach to grow CaCO3 crystals on the surface of microcellulose ьш is demonstrated opening broad avenues for the development of vaterite coatings technologies.

A Bio‐Inspired Magnetically Recoverable Palladium Nanocatalyst for the Ullmann Coupling reaction of Aryl halides and Arylboronic acids In Aqueous Media

AbstractPalladium nanoparticles supported on polydopamine‐coated iron oxide nanoparticles (Pd/Fe3O4@PDA) were found to catalyze the Ullmann homocoupling of a wide variety of aryl halides, arylboronic acids and aryldiazonium salts in aqueous media in the presence of randomly methylated β‐cyclodextrin (RM‐β‐CD). The synthesized nanoparticles were characterized by techniques such as TEM, SEM, EDX, XPS, ICP‐AES and XRD. The synthesized catalyst can be easily recovered magnetically and reused up to five cycles without any significant loss of activity. This is the first report demonstrating the use of magnetically recoverable catalyst for Ullmann homocoupling reactions of aryl halides, arylboronic acids and aryldiazonium salts in water.

Comparison of advanced oxidation processes for degrading Ponceau S dye. Application of photo-Fenton process.

The major part of this work is devoted to the examination of the degradation of Ponceau S (PS) in aqueous medium by using the photo-Fenton process. The influence of pH of the medium, oxidant dose (H2O2), ferrous ion dose and the presence of inorganic ions such as bicarbonate, sulphate and nitrate on degradation kinetics was also analyzed. Before that, the efficiency of this process was compared to three other advanced oxidation processes (AOPs) such as H2O2/UV, Fenton (Fe2+/H2O2), and solar photo-Fenton. It was found that all dye degradation kinetics obeyed a pseudo-first order, and their apparent rate constants were represented by the ratios: kapp (H2O2/UV/Fe2+) =0.295 kapp (sunlight/Fe2+/H2O2) =0.141 kapp (Fe2+/H2O2) = 0.111 kapp (H2O2/UV) =0.031.Under reference conditions (0.06 mM of PS in ultrapure water), photo-Fenton oxidation using 0.06 mM of Fe2+, 1mM of H2O2 and the pH optimal value of 3 yielded more than 94.3% in only10 min of dye degradation with an apparent rate constant of 0.2951 min-1. Elsewhere, the addition of the salts in aqueous medium has, in general, an inhibition effect on the decolorization kinetics due to controlled ionic interactions of metals with inorganic ions. The most adverse effect on PS disappearance rate was observed when bicarbonate ions were present in the treated medium.

The effect of salts in aqueous media on the formation of the BSA corona on SiO2 nanoparticles

Protein-nanoparticle interactions are garnering attention due to their potential impacts on human health and environmental contamination. The colloidal properties of nanoparticles (NPs) in aqueous media may differ in the presence of natural materials such as salts and proteins. In this study, the interactions between bovine serum albumin (BSA) and fumed hydrophilic silicon dioxide (SiO2) NPs were studied in aqueous solutions under variable pH or ion composition. Investigation of hydrodynamic diameter and zeta potential changes to nanoparticles upon addition of BSA, the adsorption of BSA to the SiO2 NP surface, and the interaction energy between particles revealed that buffered solutions promote protein adsorption onto NPs and particle agglomeration. The effects of ionic salt solutions were dependent on the ion charge, with negatively charged ions stabilizing the system and positively charged ions promoting protein-nanoparticle interactions. These data highlight that physiologically relevant salts affect protein corona formation on non-toxic, amorphous SiO2 NPs and spur the need for well-defined characterization conditions when determining potential toxicity of NPs upon human or animal exposure.

Effect of Maltodextrin and Temperature on Micellar Behavior of Bile Salts in Aqueous Medium: Conductometric and Spectrofluorimetric Studies

Abstract Conductivity and fluorescence probe techniques have been employed to study the micellar behavior of bile salts i.e. sodium cholate (1–20 mmol⋅kg−1) and sodium deoxycholate (0.5–10.0 mmol⋅kg−1) in aqueous solutions of maltodextrin (0.0, 0.5, 1.1, and 1.6 mmol⋅kg−1) at different temperatures. The influence of maltodextrin on the micellization behavior of bile salts has been determined in terms of critical micelle concentration (CMC) values obtained from conductivity measurement. The variation in CMC values has been discussed by considering the alteration in the hydrophobic environment of maltodextrin-sodium cholate/sodium deoxycholate complex imparted by the carbohydrate molecules. In order to substantiate the CMC values determined from conductivity method, the fluorescence probe study of aqueous sodium cholate and sodium deoxycholate solutions in presence of fluorescent, pyrene has also been carried. The CMC values obtained from both techniques are in full agreement with each other. Moreover, application of charged pseudo-phase separation model has been made to discuss the thermodynamics of the system.

Ionic Conductivity, Diffusion Coefficients, and Degree of Dissociation in Lithium Electrolytes, Ionic Liquids, and Hydrogel Polyelectrolytes.

The conductive and diffusional behavior of electrolytes in media with different dielectric and viscoelastic properties is investigated. A revised model to separate the contribution of dissociated and nondissociated species to the diffusion coefficients determined with NMR is proposed. Impedance spectroscopy is used to measure the ionic conductivity of lithium salts in aqueous medium, ionic liquids in aprotic solvents, and hydrogel polyelectrolytes. The diffusion coefficients of the species of interest in those systems are determined with multinuclear pulsed-gradient spin-echo (PGSE) NMR. The results are analyzed using the revised model. It is shown that the degree of ionization could be determined directly from measurements of ionic conductivity and diffusion coefficients in very different types of electrolytes and in a wide range of concentrations. Furthermore, these findings support the original Arrhenius hypothesis about electrolytes and show that the assumption of a complete dissociation is not required to describe their conductive behavior. The reduced conductivity observed in hydrogels, at or near swelling equilibrium, compared to that in solutions could be attributed mainly to the hindered ionic mobility caused by the network structure.

Anion influence on polymerization of Cd(II) picolinamide complexes

Abstract The reactions of picolinamide (pyridine-2-carboxamide, pia) with various cadmium(II) salts in aqueous media were investigated. With cadmium(II) halides, three novel coordination polymers (CPs) were isolated, namely: [CdX2(pia)]n (X = Cl (1), Br (2), I (3). Cadmium(II) sulphate gave [Cd(SO4)(pia)(H2O)3] ·2H2O (4) while cadmium(II) nitrate in the presence of perchlorate ions gave mixed complex [Cd(pia)3(H2O)](NO3)(ClO4) (5) with both anions acting as counterions. All isolated complexes were identified by chemical analysis and characterized using IR-spectroscopy and thermal methods (TG/DSC). X-ray crystal structure analysis of 1–3 revealed a distorted octahedral coordination of Cd(II) which consists of four halide and N,O-chelated pia ligands. The chain propagation is achieved through metal-halide double-bridges. The pia ligand is in cis geometry (cis-configured polymeric chain) and the topology of chains can be described as zig-zag. In 1 the neighbouring chains are mutually linked through weak C H···Cl and N H···Cl hydrogen bonds into 3D supramolecular framework. In 2 and 3, which are isostructural, unlike in 1 the neighbouring chains are linked by a strong head-to-head amide hydrogen bonds (graph set R22(8)) into supramolecular sheets in (0 1 0) planes and through weak C H···X interactions a 3D supramolecular framework is accomplished. In discrete molecules of 4 and 5, a distorted octahedral and pentagonal bipyramidal coordination of Cd(II) ion is revealed respectively. The final 3D supramolecular dimensionality of 4 and 5 is achieved through non-covalent interactions including sulphate ions in the former, and perchlorate and nitrate ions in the later thus pointing a discernible influence of anions on the structure.

Reducing the ordering temperature of FePt nanoparticles by Cu additive and alternate reduction method

(FePt)[Formula: see text]Cu[Formula: see text] nanoparticles were successfully prepared by alternate reduction of metal salts in aqueous medium. Detailed investigations on the correlation between the magnetic and structural properties of these nanoparticles are presented as a function of annealing temperature. Both the X-ray diffraction patterns and the magnetic hysteresis loop measurements show the existence of L10-FePt phase at a relative low annealing temperature. It is proved that the Cu additive and alternate reduction are very effective methods in reducing the ordering temperature of FePt nanoparticles.

Influence of the Immersion Time and Temperature on the Corrosion of API X52 Steel in an Aqueous Salt Medium

Influence of the Immersion Time and Temperature on the Corrosion of API X52 Steel in an Aqueous Salt Medium

Formation and shape-control of hierarchical cobalt nanostructures using quaternary ammonium salts in aqueous media

Aggregation and self-assembly are influenced by molecular interactions. With precise control of molecular interactions, in this study, a wide range of nanostructures ranging from zero-dimensional nanospheres to hierarchical nanoplates and spindles have been successfully synthesized at ambient temperature in aqueous solution. The nanostructures reported here are formed by aggregation of spherical seed particles (monomers) in presence of quaternary ammonium salts. Hydroxide ions and a magnetic moment of the monomers are essential to induce shape anisotropy in the nanostructures. The cobalt nanoplates are studied in detail, and a growth mechanism based on collision, aggregation, and crystal consolidation is proposed based on a electron microscopy studies. The growth mechanism is generalized for rods, spindles, and nearly spherical nanostructures, obtained by varying the cation group in the quaternary ammonium hydroxides. Electron diffraction shows different predominant lattice planes on the edge and on the surface of a nanoplate. The study explains, hereto unaddressed, the temporal evolution of complex magnetic nanostructures. These ferromagnetic nanostructures represent an interesting combination of shape anisotropy and magnetic characteristics.