Salts In Aqueous Media Research Articles

Síntese de biofilmes de Quitosana reticulados com Tripolifosfato atuando como agente quelante na fixação de nanopartículas de Prata

Silver nanoparticles have been incorporated in the various materials, using different complexation agents. The work aims at the incorporation of silver nanoparticles in biofilms of chitosan using as agent crosslinker and complexing sodium tripolyphosphate. We used the method of reduction of silver salts in aqueous medium for synthesis of nanoparticles, determining the through the analysis of their plasmonic band by UV-Vis spectrophotometry. In order to compare the efficiency of tripolyphosphate was used biofilms non-crosslinked and filter paper as material control. The analyses in UV-Vis showed the presence of a single plasmon band centered around 400 nm, which is indicative of nanoparticles with spherical shape. Studies of incorporation of the silver nanoparticles showed the efficiency of tripolyphosphate in fixing, complexing all the silver colloidal solution tested in comparison to others materials, thus proving the efficiency of tripolyphosphate as a chelating agent in the fixation of silver nanoparticles. Keywords: Silver nanoparticles, chitosan, tripolyphosphate, polymer, adsorption.

Complexes of star-shaped cationic polyelectrolytes with anionic liposomes: Towards multi-liposomal assemblies with controllable stability

Complexes were formed via the electrostatic interaction between 30–50 nm anionic liposomes and a star-shaped polyelectrolyte, poly{[2-(methacryloyloxy)ethyl]trimethyl ammonium iodide}, having cationic arms that radiate from a silicon-based central core. The complexation was investigated with attention given to assessing the capacity of the cationic stars for the anionic liposomes (both liquid and solid); the integrity of the complexed liposomes; and the stability of the resulting star/liposome complexes in aqueous salt solutions. We have found that by changing the content of anionic groups in the liposomal membrane as well as the phase-state of membrane, the stability of star/liposome complexes in aqueous salt media can be controlled. The liquid liposomes with 0.1 mol fraction of anionic palmitoyloleoylphosphatidylserine (POPS1−), and solid liposomes with 0.1 mol fraction of POPS1−, retain their integrity when bound to the stars, with the resulting star/liposome complexes being stable in physiological solution, i.e. [NaCl] = 0.15 M. Multi-liposomal complexes containing up to 12 liposomes per star seem to hold promise as carriers for biologically active compounds.

Electrografted P4VP as Dielectric in High Aspect Ratio TSV: Surface Preparation and Thermomechanical Consideration

A challenge to most 3D integration approaches is the deposition of the Through-Silicon-Via (TSV) dielectric layer. A TSV is traditionally electrically insulated from the silicon substrate by a thin SiO2 film. As TSV aspect ratio gets higher, conformal SiO2 dielectric deposition becomes much more challenging. Alchimer has proposed as dielectric, the use of a highly conformal organic (poly-4-vinylpyridine, P4VP) as dielectric, electrografted through electrochemical reduction of diazonium salts in aqueous media. Surface cleaning prior to electrografting process is a challenge, especially in via last approach. Moreover, the thermomechanical behavior of P4VP coated TSVs remains unknown. This information is most relevant for the layout optimization of 3D integrated microsystems. We will discuss the TSV surface preparation challenge prior to the electrografting process and present the first measurements of the stress induced in the silicon substrate around TSV insulate by P4VP.

Binding of carboxylatopillar[5]arene with alkyl and aryl ammonium salts in aqueous medium

Alkyl ammonium salts exhibited strong binding with carboxylatopillar[5]arene in aqueous medium which resulted in the formation of pseudo[2]rotaxane and pseudo[3]rotaxane species.

Spectroscopic investigation of interaction of Nile Blue A, a potent photosensitizer, with bile salts in aqueous medium

Nile Blue A (NB) is one of the most studied benzophenoxazine dyes, as a potent photosensitizer for photodynamic therapy. The dye when administered intravenously disperses throughout the body by circulating through blood and is taken up by most cells that emphasize its interaction with various biomolecules. Therefore a rational understanding of the interaction of NB with relevant biological and biomimicking systems appears important. The focus of the present work is to investigate the interaction of NB with two bile salts sodium deoxycholate (NaDC) and sodium cholate (NaC) by spectroscopic techniques. The bile salts, in their premicellar concentration range, induce NB dimerization. Both H- and J-dimers are formed, however a major contribution is from the H-dimers. The extent of NB dimerization in NaDC, the dihydroxy bile salt, is higher than that in NaC, the trihydroxy bile salt. The bile salts when present above their micellar concentrations solubilize NB in its monomeric form. NB exhibits stronger binding and partitioning efficiency toward NaDC than NaC micelles at a given temperature. Binding and partitioning of NB to these micelles are spontaneous and exothermic in nature and these are enthalpy-driven processes. The spectral profiles and thermodynamic parameters of NB point toward the dissimilar nature of its environment in the micelles formed by the above two bile salts.

Visible light catalysis-assisted assembly of Ni(h)-QD hollow nanospheres in situ via hydrogen bubbles.

Hollow spheres are one of the most promising micro-/nanostructures because of their unique performance in diverse applications. Templates, surfactants, and structure-directing agents are often used to control the sizes and morphologies of hollow spheres. In this Article, we describe a simple method based on visible light catalysis for preparing hollow nanospheres from CdE (E = Te, Se, and S) quantum dots (QDs) and nickel (Ni(2+)) salts in aqueous media. In contrast to the well-developed traditional approaches, the hollow nanospheres of QDs are formed in situ by the photogeneration of hydrogen (H2) gas bubbles at room temperature. Each component, that is, the QDs, metal ions, ascorbic acid (H2A), and visible light, is essential for the formation of hollow nanospheres. The quality of the hollow nanospheres depends on the pH, metal ions, and wavelength and intensity of visible light used. Of the various metal ions investigated, including Cu(+), Cu(2+), Fe(2+), Fe(3+), Ni(2+), Mn(2+), RuCl5(2-), Ag(+), and PtCl4(2-), Ni(2+) ions showed the best ability to generate H2 and hollow-structured nanospheres under visible light irradiation. The average diameter and shell thickness of the nanospheres ranged from 10 to 20 nm and from 3 to 6 nm, respectively, which are values rarely reported in the literature. Studies using high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), inductively coupled plasma-mass spectroscopy (ICP-AES), and steady-state and time-resolved spectroscopy revealed the chemical nature of the hollow nanospheres. Additionally, the hollow-structured nanospheres exhibit excellent photocatalytic activity and stability for the generation of H2 with a rate constant of 21 μmol h(-1) mg(-1) and a turnover number (TON) of 137,500 or 30,250 for CdTe QDs or nickel, respectively, under visible light irradiation for 42 h.

Alkyl carboxylates as efficient and green inhibitors of magnesium alloy ZE41 corrosion in aqueous salt solution

Long chain alkyl carboxylates like stearate, palmitate and myristate were investigated for their efficiency in inhibiting the corrosion of magnesium alloy ZE41 in an aqueous salt medium containing 0.2M Na2SO4 and 0.1M NaCl. The techniques like potentiodynamic polarization and EIS, along with SEM and EDX analyses were employed. The inhibition was proposed to be the result of adsorption of alkyl carboxylates, which was found to obey the Langmuir adsorption isotherm. The inhibition was assumed to be the outcome of the formation of a compact modified surface film due to the precipitation of adsorbed alkyl carboxylates of magnesium.

Performances of carbon-based screen-printed electrodes modified by diazonium salts with various carboxylic functions for trace metal sensors

The electrochemically induced functionalization of carbon-based screen-printed-electrodes (SPEs) by phenyl groups, having one or two carboxylic functions, was achieved by reduction of in situ generated diazonium salts in aqueous media. The corresponding diazonium cations of 4-aminobenzoic acid, 4-aminophthalic acid, 3-(4-aminophenyl) propionic acid, 3-(4-aminophenyl)-2-propenoic acid and 5-aminoisophthalic acid were generated in situ with sodium nitrite in aqueous H2SO4. The electrochemical detection of Pb(II) with the grafted SPEs was investigated using Pb(II) 5×10−8M solutions. The performances of the grafted SPEs were found to be dependent on the number of carboxylic groups, on their position on the phenyl ring, on the olefinic or the aliphatic character of the chain bearing the carboxylic group. The performances of mono-4-carboxyphenyl and 3,5-dicarboxyphenyl grafted SPEs for Cd(II) and Cu(II) trace detection were tested and compared.

Low-temperature ordering of FePt nanoparticles by alternate reduction of metal salts in aqueous medium

FePt nanoparticles have been successfully synthesized by the alternate reduction of chloroplatinic acid and ferric chloride, in the presence of acetyl trimethyl ammonium bromide as a surfactant in aqueous medium. Detailed investigations on the structural and magnetic properties of these nanoparticles were presented as a function of annealing temperature. Selected area electron diffraction shows the initiation of phase transition from the as-synthsized phase to ordered face center tetragonal (FCT) at 400°C. The x-ray diffraction and magnetic measurements confirm the transformation to FCT phase at 400°C. The magnetic measurements at room temperature show a double phase hysteresis loop at 400°C and a nearly single phase hysteresis loop at 600°C, with the coercivity of about 3.4kOe and 16.2kOe, respectively. We report for the first time this alternate reduction method in synthesizing FePt nanoparticles, obtained a decrease of about 100°C in the ordering temperature.

Cationic polymerization of isobutyl vinyl ether coinitiated with heteropolyacid or its salts in aqueous medium

The suspension cationic polymerization of isobutyl vinyl ether (IBVE) in aqueous medium could be achieved by using H3PW12O40, AlPW12O40, FePW12O40, K3PW12O40, or Na3PW12O40 as efficient water-tolerant coinitiators in the presence of HCl. The addition reaction of IBVE with H2O occurred to form IBVE–H2O adduct and then subsequent decomposition immediately took place or turned to acetaldehyde diisobutyl acetal (A) in the presence of AlPW12O40, and (A) decomposed rapidly to form 2-isobutanol (B) and acetaldehyde (C). Cationic polymerization of IBVE in aqueous medium was promoted greatly with increasing HCl concentration and proceeded extremely rapidly to get high polymer yield even at low concentration of AlPW12O40 of 0.3 mM. A sufficient amount of HCl was needed to decrease the hydrolysis of initiator IBVE–HCl and to accelerate the polymerization in aqueous medium simultaneously. The yield and molecular weight of poly(IBVE) increased with increasing concentrations of HCl and AlPW12O40 or with decreasing temperature. The isotactic-rich poly(IBVE)s with m diad of around 60%, having Mn of 1200–4500 g mol−1 and monomodal molecular weight distribution could be obtained via cationic polymerization of IBVE in aqueous medium. This is the first example of cationic polymerization of IBVE in aqueous medium coinitiated by heteropolyacid and its salts. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

Physicochemical studies on the catanionics of alkyltrimethylammonium bromides and bile salts in aqueous media

Phase manifestation and aggregation behavior of long chain alkyltrimethylammonium bromides (CnTABr, n=12, 14 and 16) in combination with sodium cholate (NaC) and sodium deoxycholate (NaDC), were studied in aqueous medium. CnTABr–NaDC mixed systems exhibited different phases, viz., micelles, vesicles and precipitates while only clear isotropic phase was formed with NaC. With increasing chain length of CnTABr, both the area under precipitate and viscous zones increased. Micellization behavior of mixed surfactant systems at different compositions were studied by conductance, viscosity, fluorescence spectroscopy, dynamic light scattering, zeta potential and small angle X-Ray scattering measurements. Mixed micelles, at all combinations, were basically comprised of larger proportion (∼50–60%) of cationic surfactant, which were independent of the bulk composition. Interaction parameter, activity coefficient and micellar composition were evaluated in the light of Rubinigh's model for Regular Solution Theory (RST). Strong synergistic interaction occurred between CnTABr and bile salts where NaC behaved differently from NaDC due to its higher hydrophilicity. Complexity of the different systems increased with the increasing chain length of CnTABr. Such catanionic systems are considered to have prospects in drug delivery systems, nanoparticle synthesis, etc.

Hydration structures of U(III) and U(IV) ions from ab initio molecular dynamics simulations

We apply DFT+U-based ab initio molecular dynamics simulations to study the hydration structures of U(III) and U(IV) ions, pertinent to redox reactions associated with uranium salts in aqueous media. U(III) is predicted to be coordinated to 8 water molecules, while U(IV) has a hydration number between 7 and 8. At least one of the innershell water molecules of the hydrated U(IV) complex becomes spontaneously deprotonated. As a result, the U(IV)-O pair correlation function exhibits a satellite peak at 2.15 Å associated with the shorter U(IV)-(OH(-)) bond. This feature is not accounted for in analysis of extended x-ray absorption fine structure and x-ray adsorption near edge structure measurements, which yield higher estimates of U(IV) hydration numbers. This suggests that it may be useful to include the effect of possible hydrolysis in future interpretation of experiments, especially when the experimental pH is close to the reported hydrolysis equilibrium constant value.

Role of the Hofmeister Series in the Formation of Ionic-Liquid-Based Aqueous Biphasic Systems

Among the numerous and interesting features of ionic liquids is their ability to form aqueous biphasic systems (ABSs) when combined with inorganic or organic salts in aqueous media. In this work, a wide range of salts was studied, aiming at gathering a detailed picture on the molecular mechanisms that govern the ability of the salt ions to induce the formation of ionic-liquid-based ABSs. For that purpose, 1-butyl-3-methylimidazolium trifluoromethanesulfonate was chosen due to its facility to undergo liquid-liquid demixing in aqueous media containing conventional salts. The corresponding ternary phase diagrams, tie-lines, and tie-line lengths were determined at 298 K and atmospheric pressure. With the large body of data measured in this work, it was possible to establish a scale on the salt cation and anion abilities to induce the formation of ionic-liquid-based ABSs, which follows the Hofmeister series, and to show that the molar entropy of hydration of the salt ions is the driving force for aqueous two-phase system formation.

On the nature of the electrode surface modification by cathodic reduction of tetraarylporphyrin diazonium salts in aqueous media

Different substrates have been modified through electroreduction of tetraarylporphyrin diazonium salts, H2TPP-N2+ or H2TPP-(N2+)4, generated in situ in acidic aqueous media from monoamino-TPP (H2TPP-NH2) or tetraamino-TPP (H2TPP-(NH2)4) in low concentration (5.10−4M). The modification of the electrodes with H2TPP-(NH2)4 leads to a purple deposit (PolyH2TPP-1) strongly linked to the electrode surface whereas those obtained from H2TPP-NH2 were not covalently linked to the electrode surface, soluble in organic solvents and identified as tetraphenylporphyrin (H2TPP). The deposits have been characterized by electrochemistry, atomic force microscopy (AFM) and UV–Visible absorption spectroscopy. Cyclic voltammetry of PolyH2TPP-1 revealed an electroactivity akin to that of polytetraarylporphyrin obtained by anodic electropolymerization of H2TPP (~2.10−3M) in strictly anhydrous electrolytic medium (PolyH2TPP-2). In light of their UV–vis spectra, the two related polymers present different intermolecular interactions and macromolecular organization.

Environmentally friendly homocoupling reaction of functionalized potassium aryl trifluoroborates salts in aqueous media

The homocoupling reaction between potassium aryl trifluoroborates containing different functionalities promoted by a catalytic amount of Pd(OAc)2 is described. The methodology uses water as a solvent under aerobic conditions to give the corresponding biaryl compounds in good yields.

ChemInform Abstract: Efficient Synthesis of Functionalized Butenolides Mediated by Vinyltriphenylphosphonium Salts in Aqueous Media.

AbstractThe reaction of esters (II) with triphenylphosphine results in formation vinyltriphenylphosphonium salts which react with carbonyl compounds (I) or (IV) to produce highly functionalized butenolides.

Novel dimeric amide alkaloids from Piper chaba Hunter: isolation, cytotoxic activity, and their biomimetic synthesis

Chromatographic fractionation of methanol extract from roots of the Piper chaba Hunter resulted in the isolation of four new dimeric alkaloids, chabamide H ( 1), I ( 2), J ( 3), K ( 4) together with 11 known compounds ( 5– 15). Their chemical structures and relative stereochemistry were determined on the basis of the comprehensive spectroscopic techniques (IR, Mass, and NMR) and further confirmed by comparison of the data with those reported in literature. In addition, cytotoxic activities of all the dimeric amides ( 1– 7) along with their monomers ( 8– 10) were evaluated against cervical (HELA), breast (MCF-7), liver (HEPG2), colon (HT-29), and colon (COLO-205) cancer cell lines. Among the tested isolates, 5 and 7 exhibited potent cytotoxic activity against COLO-205 cell line with IC 50 value of 3.10 μg/mL and 0.018 μg/mL, respectively. To prove biogenesis of the newly isolated compounds, biomimetic synthesis has also been carried out via Diels–Alder reaction by using copper(II) salts in aqueous medium.

Efficient synthesis of functionalized butenolides mediated by vinyltriphenylphosphonium salts in aqueous media

Abstract An efficient synthesis of 5-oxo-2,5-dihydro-3-furancarboxylate derivatives via reaction of dialkyl acetylenedicarboxylate with triphenylphosphine (Ph 3 P) in the presence of activated carbonyl compounds such as ethyl pyruvate, benzil, benzoylcyanide, biacetyle or N -alkylisatins is described.

Weak C-H…F-C interactions in carboxylate anion binding: Synthesis, spectroscopic and X-ray structural studies of [Co(phen)2CO3]2 (C7H3O2FCl)Cl·11H2O and [Co(phen)2CO3](C7H3NO4Cl)·6H2O

Two new complex salts containing 2,5-substituted benzoate ions, [Co(phen)2CO3]2(C7H3O2FCl)Cl·11H2O (1) and [Co(phen)2CO3](C7H3NO4Cl)·6H2O (2) (where phen = 1,10-phenanthroline, C7H3O2FCl = 2-chloro-5-fluorobenzoate (cfbz) and C7H3NO4Cl = 2-chloro-5-nitrobenzoate(cnbz)) were synthesized by reacting carbonatobis(1,10-phenanthroline)cobalt(III) chloride with appropriate salts in aqueous medium. A detailed packing analysis has been undertaken to delineate the role of second sphere C-H…F and C-H…O interactions amid other heteroatom interactions. The complex salts have been characterized by elemental analyses, spectroscopic studies (IR, UV/Visible, multinuclear NMR), conductance and solubility product measurements. Single crystal X-ray structure determination revealed ionic structures of both the complex salts having discrete ions along with lattice water molecules. Crystal lattice is stabilized by a variety of hydrogen bonding interactions, i.e. O-H…O, C-H…O and C-H…F involving second sphere coordination besides π-π interaction. Furthermore, packing analyses reveal that C-H…F interactions can manifest even in the presence of a large number of heteroatom interactions.

Dispersion polymerization of anionic polyacrylamide in an aqueous salt medium

Anionic polyacrylamide dispersions were prepared by dispersion polymerization in an aqueous salt medium, using acrylamide(AM) and acrylic acid(AA) as monomers and anionic polyelectrolytes as stabilizer. Effects of salt concentration, and molecular weight and concentration of stabilizers on the stability of the dispersions were investigated using a HAAKE rheometer and optical microscopy. The results showed that stable anionic polyacrylamide dispersions, consisting of smooth, spherical, polydisperse particles, could be obtained under the conditions of salt concentration ranging from 26 wt% to 30 wt%, concentration of stabilizers from 1.2 wt% to 1.8 wt%, and intrinsic viscosity of stabilizers from 2.98 dL·g−1 to 3.74 dL·g−1. The apparent viscosity of the stable dispersions changed very little with the shear rate, showing Newton fluid behavior.