Solution-phase exfoliation of graphite for ultrafast photonics

We exfoliate graphite in both aqueous and non-aqueous environments through mild sonication followed by centrifugation. The dispersions are enriched with monolayers. We mix them with polymers, followed by slow evaporation to produce optical quality composites. Nonlinear optical measurements show similar to 5% saturable absorption. The composites are then integrated into fiber laser cavities to generate 630 fs pulses at 1.56 mu m. This shows the viability of solution phase processing for graphene based photonic devices. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Liquid-liquid extraction of protactinium(V) using tri-iso-octylamine

Solvent extraction of protactinium with tri-iso-octyl-amine (TIOA) in xylene, benzene, carbon tetrachloride and chloroform from HCl, HF, HNO3, HClO4 and H2SO4 media was studied using Pa-233 as a radiotracer. The extraction efficiencies of protactinium were determined as a function of shaking time, concentrations of mineral acids in aqueous phase, extractant concentrations and diluents in organic phase. The extraction mechanism was discussed. The results show that the extracted species in the organic phase is [(R3N-H)(n)Pa(OH)(x)Cl-y(5-x-y)].

An effective method for enhancing metal-ions' selectivity of ionic liquid-based extraction system: Adding water-soluble complexing agent

Selective extraction-separation of yttrium(Ill) from heavy lanthanides into 1-octyl-3-methylimidazolium hexafluorophosphate ([C(8)mim][PF6]) containing Cyanex 923 was achieved by adding a water-soluble complexing agent (EDTA) to aqueous phase. The simple and environmentally benign complexing method was proved to be an effective strategy for enhancing the selectivity of [C(n)mim] [PF6]/[Tf2N]-based extraction system without increasing the loss of [C(n)mim](+). (c) 2007 Elsevier B.V. All rights reserved.

Studies of electron-transfer and charge-transfer coupling processes at a liquid/liquid interface by double-barrel micropipet technique

Investigation of a heterogeneous electron-transfer (ET) reaction at the water/1,2-dichloroethane interface employing a double-barrel micropipet technique is reported. The chosen system was the reaction between Fe(CN)(6)(3-) in the aqueous phase (W) and ferrocene in 1,2-dichloroethane (DCE). According to the generation and the collection currents as well as collection efficiency, the ET-ion-transfer (IT) coupling process at such an interface and competing reactions with the organic supporting electrolyte in the organic phase can be studied. In addition, this technique has been found to be an efficient method to distinguish and measure the charge-transfer coupling reaction between two ions (IT-IT) processes occurring simultaneously at a liquid/liquid interface. On this basis, the formal Gibbs energies of transfer of some ions across the W/DCE interface, such as NO3-, NO2-, Cl-, COO-, TBA(+), IPAs+, Cs+, Rb+, K+, Na+, and Li+, for which their direct transfers are usually difficult to obtain because of the IT-IT coupling processes, were quantitatively evaluated.

Study of facilitated potassium ion transfer across a water vertical bar 1,2-dichloroethane interface using different phase volume ratio systems

A study of potassium ion transfer across a water \ 1,2-dichloroethane (W \ DCE) interface facilitated by dibenzo-18-crown-6 (DB18C6) with various phase volume ratio systems is presented. The key point was that a droplet of aqueous solution containing a redox couple, Fe(CN)(6)(3-)/Fe(CN)(6)(4-), with equal molar ratio, was first attached to a platinum electrode surface, and the resulting droplet electrode was then immersed into the organic solution containing a hydrophobic electrolyte to construct a platinum electrode/aqueous phase/organic phase system. The interfacial potential of the W \ DCE within the series could be externally controlled because the specific compositions in the aqueous droplet make the Pt electrode function like a reference electrode as long as the concentration ratio of Fe(CN)(6)(3-)/Fe(CN)(6)(4-) remains constant. In this way, a conventional three-electrode potentiostat can be used to study the ion transfer process at a liquid \ liquid (L \ L) interface facilitated by an ionophore with variable phase volume ratio (r = V-o/V-w). The effect of r on ion transfer and facilitated ion transfer was studied in detail experimentally. We also demonstrated that as low as 5 x 10(-8) M DB18C6 could be determined using this method due to the effect of the high phase volume ratio.

Study of electron transfer across the liquid/ice-like matrix interface by scanning electrochemical microscopy

In this work, we report the findings of a study on scanning electrochemical microscopy (SECM) to investigate the interfacial electron-transfer (ET) reaction between the 7,7,8,8-tetracyanoquinodimethane radical anion (TCNQ(.-)) in 1,2-dichloroethane and ferricyanide in an ice-like matrix (a mixture of insulting ice and conductive liquid) under low temperatures. Experimental results indicate that the formed liquid/ice-like matrix interface is superficially similar in electrochemical characteristics to a liquid/liquid interface at temperatures above -20 degreesC. Furthermore, imaging data show that the surface of the ice-like matrix is microscopically flat and physically stable and can be applied as either a conductive or an insulting substrate for SECM studies. Perchlorate ion was selected as the common ion in both phases, the concentrations of which controlled the interfacial potential difference. The effect of perchlorate concentration in the DCE phase on interfacial reactions has been studied in detail. The apparent heterogeneous rate constants for TCNQ(.-) oxidation by Fe(CN)(6)(3-) in another phase under different temperatures have been calculated by a best-fit analysis, where the experimental approach curves are compared with the theoretically derived relationships. Reaction rate data obey Butler-Volmer formulation before and after the freezing point, which is similar to most other known cases of ET reactions at liquid/liquid interfaces. However, there is a sharp change observed for heterogeneous rate constants around the freezing point of the aqueous phase, which reflects the phase transition. At temperatures below -20 degreesC, surface-confined voltammograms for the reduction of ferricyanide were obtained, and the ice-like matrix became an insulating one, which indicates that the aqueous phase is really a frozen phase.

The kinetics study in liquid-liquid systems with constant interfacial area cell with Laminar flow

A novel constant interfacial cell with laminar flow is proposed as an approach to obtain extraction kinetics data in liquid-liquid systems. Applications and theoretical fundamentals of the apparatus have been elaborated.. The equation which can express the mass transfer of liquid-liquid system run in the constant interfacial cell with laminar flow is deduced. Simulations from the equations indicate that diffusivity is a suitable factor to represent the characteristics of extraction kinetics rather than the extraction rate in the diffusion controlling step. The dependence of the aqueous phase concentration on time is recommended to determine the extraction regime. The diffusivities of the EuCl3-HDEHP extraction system obtained by different methods are compared to certify the hydrodynamic theory of the cell. The diffusivities of the ErCl3-HEH/EHP extraction system are determined, which show that this technique is a convenient method to obtain the diffusivities in the liquid-liquid system and to determine the extraction regime. (C) 1998 Elsevier Science Ltd. All rights reserved.

ELECTROCHEMICAL INVESTIGATION OF LIQUID/LIQUID SYSTEMS USING VARIOUS ORGANIC SOLVENTS

The potential windows of the system water/pure solvent (W/P) and water/solvent mixtures(W/S) have been investigated by cyclic voltammetry with solvents whose dielectric constants lie between 5.87 and 34.82. In the presence of LiCI in the aqueous phase and tetrabutytammoniumtetraphenylborate(TBATPB) in the organic phase, the systems water/allyl iso-thiocyanate (W/AIT) and water/nitrobensene (W/NB) show a same wide epotential window. thermodynamic parameters of ion transfer W/AIT interface were determined. In systems of W/P and V/S the influence solvent effect on the standard gibbs energies of transfer of was discussed.

Task-specific ionic liquid for solubilizing metal oxides

Protonated betaine bis(trifluoromethylsulfonyl) imide is an ionic liquid with the ability to dissolve large quantities of metal oxides. This metal-solubilizing power is selective. Soluble are oxides of the trivalent rare earths, uranium(VI) oxide, zinc(II) oxide, cadmium( II) oxide, mercury( II) oxide, nickel( II) oxide, copper(II) oxide, palladium(II) oxide, lead(II) oxide, manganese( II) oxide, and silver( I) oxide. Insoluble or very poorly soluble are iron(III), manganese(IV), and cobalt oxides, as well as aluminum oxide and silicon dioxide. The metals can be stripped from the ionic liquid by treatment of the ionic liquid with an acidic aqueous solution. After transfer of the metal ions to the aqueous phase, the ionic liquid can be recycled for reuse. Betainium bis( trifluoromethylsulfonyl) imide forms one phase with water at high temperatures, whereas phase separation occurs below 55.5 degrees C ( temperature switch behavior). The mixtures of the ionic liquid with water also show a pH-dependent phase behavior: two phases occur at low pH, whereas one phase is present under neutral or alkaline conditions. The structures, the energetics, and the charge distribution of the betaine cation and the bis( trifluoromethylsulfonyl) imide anion, as well as the cation-anion pairs, were studied by density functional theory calculations.

Changed reactivity of the 1-bromo-4-nitrobenzene radical anion in a room temperature ionic liquid

Radical anions of 1-bromo-4-nitrobenzene (p-BrC6H4NO2) are shown to be reactive in the room temperature ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, ([C(4)mPyrr][NTf2]), by means of voltammetric measurements. In particular, they are shown to react via a DISP type mechanism such that the electrolysis of p-BrC6H4NO2 occurs consuming between one and two electrons per reactant molecule, leading to the formation of the nitrobenzene radical anion and bromide ions. This behaviour is a stark contrast to that in conventional non-aqueous solvents such as acetonitrile, dimethyl sulfoxide or N,N-dimethylformamide, which suggests that the ionic solvent promotes the reactivity of the radical anion, probably via stabilisation of the charged products.

Development of a heterogeneous catalyst for lignocellulosic biomass conversion:Glucose dehydration by metal chlorides in a silica-supported ionic liquid layer

An attempt is made to immobilize the homogeneous metal chloride/EMIMCl catalyst for glucose dehydration to 5-hydroxymethylfurfural. To this end, ionic liquid fragments were grafted to the surface of SBA-15 to generate a heterogenized mimick of the homogeneous reaction medium. Despite a decrease in the surface area, the ordered mesoporous structure of SBA-15 was largely retained. Metal chlorides dispersed in such ionic liquid film are able to convert glucose to HMF with much higher yields as is possible in the aqueous phase. The reactivity order CrCl > AlCl > CuCl > FeCl is similar to the order in the ionic liquid solvent, yet the selectivity are lower. The HMF yield of the most promising CrCl-Im-SBA-15 can be improved by using a HO:DMSO mixture as the reaction medium and a 2-butanol/MIBK extraction layer. Different attempts to decrease metal chloride leaching by using different solvents are described. © 2013 American Institute of Chemical Engineers Environ Prog.

Preparation of Aqueous Core/Polymer Shell Microcapsules by Internal Phase Separation

Aqueous core/polymer shell microcapsules with mommuclear and polynuclear core morphologies have been formed by internal phase separation from water-in-oil emulsions. The water-in-oil emulsions were prepared with the shell polymer dissolved in the aqueous phase by adding a low boiling point cosolvent. Subsequent removal of this cosolvent (by evaporation) leads to phase separation of the polymer and, if the spreading conditions are correct, formation of a polymer shell encapsulating the aqueous core. Poly(tetrahydrofuran) (PTHF) shell/aqueous core microcapsules, with a single (mononuclear) core, have been prepared, but the low T-g (-84 degreesC) of PTHF makes characterization of the particles more difficult. Poly(methyl methacrylate) and poly(isobutyl methacrylate) have higher T-g values (105 and 55 degreesC, respectively) and can be dissolved in water at sufficiently high acetone concentrations, but evaporation of the acetone from the emulsion droplets in these cases mostly resulted in polynuclear capsules, that is, having cores with many very small water droplets contained within the polymer matrix. Microcapsules with fewer, larger aqueous droplets in the core could be produced by reducing the rate of evaporation of the acetone. A possible mechanism for the formation of these polynuclear cores is suggested. These microcapsules were prepared dispersed in an oil-continuous phase. They could, however, be successfully transferred to a water-continuous phase, using a simple centrifugation technique. In this way, microcapsules with aqueous cores, dispersed in an aqueous medium, could be made. It would appear that a real challenge with the water-core systems, compared to the previous oil-core systems, is to obtain the correct order of magnitude of the three interfacial tensions, between the polymer, the aqueous phase, and the continuous oil phase; these control the spreading conditions necessary to produce shells rather than "acorns".

Fecal water as a non-invasive biomarker in nutritional intervention: comparison of preparation methods and refinement of different endpoints

The assessment of cellular effects by the aqueous phase of human feces (fecal water, FW) is a useful biomarker approach to study cancer risks and protective activities of food. In order to refine and develop the biomarker, different protocols of preparing FW were compared. Fecal waters were prepared by 3 methods: (A) direct centrifugation; (B) extraction of feces in PBS before centrifugation; and (C) centrifugation of lyophilized and reconstituted feces. Genotoxicity was determined in colon cells using the Comet assay. Selected samples were investigated for additional parameters related to carcinogenesis. Two of 7 FWs obtained by methods A and B were similarly genotoxic. Method B, however, yielded higher volumes of FW, allowing sterile filtration for long-term culture experiments. Four of 7 samples were non-genotoxic when prepared according to all 3 methods. FW from lyophilized feces and from fresh samples were equally genotoxic. FWs modulated cytotoxicity, paracellular permeability, and invasion, independent of their genotoxicity. All 3 methods of FW preparation can be used to assess genotoxicity. The higher volumes of FWobtained by preparation method B greatly enhance the perspectives of measuring different types of biological parameters and using these to disclose activities related to cancer development.

Synthesis of beaded poly(vinyl ether) solid supports with unique solvent compatibility

Poly(vinyl ether) gels SLURPS (Superior Liquid Uptake Resin for Polymer-supported synthesis) with low cross-linking levels have been synthesized for the first time in beaded form using a non-aqueous inverse suspension polymerisation approach. The synthetic protocol was optimized with regards to several parameters including reactions conditions, type and concentration of suspension stabilizer and controlled low temperature addition of co-initiator. Particle size measurements confirm the production of beads with average diameters of 700e950 mm. Optimization of the monomer composition of the poly (vinyl ether) gels resulted in a novel beaded polymer support with considerably improved as well as unique swelling characteristics in solvents ranging from hexane to water. The synthetic utility of the new gel was confirmed by carrying out a set of transformations with complete conversion leading to a useful amino and hydroxy terminated solid-phase precursor resin. Reaction progress could be monitored easily by 1H and 13C gel-phase NMR.

Liquid-liquid equilibria for systems composed of refined soybean oil, free fatty acids, ethanol, and water at different temperatures

Soybean oil can be deacidified by liquid-liquid extraction with ethanol. In the present paper, the liquid-liquid equilibria of systems composed of refined soybean oil, commercial linoleic acid, ethanol and water were investigated at 298.2 K. The experimental data set obtained from the present study (at 298.2 K) and the results of Mohsen-Nia et al. [1] (at 303.2 K) and Rodrigues et al. [2] (at 323.2 K) were correlated by applying the non-random two liquid (NRTL) model. The results of the present study indicated that the mutual solubility of the compounds decreased with an increase in the water content of the solvent and a decrease in the temperature of the solution. Among variables, the water content of the solvent had the strongest effect on the solubility of the components. The maximum deviation and average variance between the experimental and calculated compositions were 1.60% and 0.89%, indicating that the model could accurately predict the behavior of the compounds at different temperatures and degrees of hydration. (C) 2010 Elsevier B.V. All rights reserved.