Aqueous Solution Phase Research Articles

A novel electroless method for the deposition of single-crystalline platinum nanoparticle films on an organic solid matrix in the presence of gold single crystals

Single-crystalline platinum nanoparticles (Pt-NPs) were directly deposited on and inside an organic solid matrix by a novel electroless galvanic method. The reducing agent was a solid phase confined with both a reducing agent and a stabilizer combined with initially deposited minute gold single crystals (Au-SCs) on the surface (Au-SM). The oxidizing agent (K2PtCl4) was in the aqueous solution phase. The reaction was carried out at the solid–liquid interface system at 80 °C and pH 1. The deposited Pt-NPs formed a uniform silver-grey conductive coating on the top of the Au-SM when the concentration of K2PtCl4 in the solution was 50 mM. The film consisted of single-crystalline Pt-NPs nearly identical in shape and size (∼250 nm). The initially deposited minute Au-SCs by the electroless deposition process were found to catalyze the formation of Pt-NPs having fcc crystal structures with dominating {111} crystal facets. The formation of Pt-NPs was not observed in the absence of initially deposited Au-SCs on the solid matrix. This method was also applicable for the deposition of deep ruby-red, optically transparent and mechanically stable Pt-NPs on and inside the Au-SM for lower concentrations of K2PtCl4 (1 to 5 mM) in the solution phase. This characteristic color was due to the strong surface plasmon absorption of Pt-NPs in the visible range. The Pt atoms initially deposited on the surface and diffused through the entire Au-SM to the opposite side that was not in contact with the oxidizing agent during the period of the reaction. The Pt-NPs on the solution-side of the Au-SM were partially naked and stabilized only from the bottom side, i.e., the upper sides of these nanocrystals were free from the stabilizer coating. The Au-SCs immobilized thiol-based epoxy resin was used as the Au-SM. The proposed Au-SM method was also applicable for the formation of ruby-red iron, palladium and beautiful, rainbow-like colorful silver nanoparticles on the Au-SM surface.

Quantum chemical analysis of carbon dioxide absorption into aqueous solutions of moderately hindered amines

Abstract Aqueous solutions of moderately hindered amines are promising absorbents for the capture of CO 2 from a gas stream because of their relatively low heats of reaction and high rates of absorption. To determine the reaction mechanisms underlying the absorption process, we performed a quantum chemical analysis of the absorption of CO 2 into aqueous amine solutions and carried out an experimental comparison of representative amines. We correlated properties such as absorption capacity and product ratio with results from free energy calculations using the conductor-like screening model for real solvents (COSMO-RS) coupled with density functional theory (DFT). Additionally, the reaction mechanisms were investigated by transition state optimizations and intrinsic reaction coordinate (IRC) calculations in an aqueous solution phase by DFT calculations using the latest continuum solvation model (SMD/IEF-PCM). The results indicated that a bicarbonate anion likely forms directly by the reaction of CO 2 , H 2 O and an amine rather than by the hydrolysis of a carbamate anion.

A novel electroless method for the deposition of single-crystalline gold nanocrystals on and inside an organic solid-matrix

Single-crystalline gold nanocrystals were directly deposited by a novel electroless galvanic method on and inside an organic solid matrix (SM) confined with both a reducing agent and a stabilizer. The reducing agent and stabilizer were in the solid phase, and the oxidizing agent (HAuCl4) was in the aqueous solution phase. The reaction was carried out at the solid–liquid interface at 60 °C and pH 1. This method differs from the classical electroless galvanic displacement deposition process in several ways. (1) The deposited gold atoms penetrate and form nanoparticles, Au-NPs, through aggregation inside the SM. (2) The galvanic process occurs at the organic polymer matrix/metal ion solution interface instead of at the inorganic material/metal ion solution interface. (3) The entire SM participates in the deposition of gold nanocrystals on and inside the organic SM. (4) Proton transfer is accompanied by gold deposition from the solid to the solution phase to maintain the overall electrical neutrality of the system. (5) Single-crystalline gold nanocrystals are deposited on and inside the SM. The proposed method is applicable to the deposition of large gold nanosheets, Au-NSs (up to 50 μm in diameter), together with Au-NPs on the top of the SM. The Au-NPs inside the SM are three-dimensionally stabilized. The nanocrystals on the solution-side of the SM are partially naked and stabilized only from the bottom side, i.e., the upper sides of these nanocrystals are free from stabilizer coating. Both thiol- and amine-based epoxy resins were used as solid matrices. This method is applicable to direct deposition of optically transparent and mechanically stable Au-NPs on and inside a SM with a lower concentration of HAuCl4 (0.1 to 0.3 mM) in the solution phase. The formation of platinum and palladium nanoparticles was only possible with this SM method when the reaction was carried out in the presence of a few gold nanocrystals on the surface of the SM.

Temperature-controlled ionic liquid-based dispersive liquid-phase microextraction, preconcentration and quantification of nano-amounts of silver ion by using disulfiram as complexing agent

Microextraction and preconcentration of Ag+ by using temperature-controlled ionic liquid-based dispersive liquid-phase microextraction (TCIL-DLPME) method is reported. It was found that tetraethylthiuram disulfide (disulfiram) dissolved in 1-hexyl-3-methylimidazolium hexaflorophosphate, [C6mim][PF6] was useful as extracting media. Graphite furnace atomic absorption spectroscopy was used to quantify Ag+. To improve extraction efficiency, different experimental factors, such as volume of ionic liquid phase, pH and volume of aqueous solution, cooling and centrifugation periods, and dissolving temperature were investigated. The calibration curve was linear in the concentration range of 6.0–100.0 ng l−1 of Ag+. Relative standard deviation (n = 7), detection limit, and preconcentration factor for determination of Ag+ were found to be 4.5%, 5.2 ng l−1, and 120, respectively. The method was successfully applied for determination of Ag+ in drinking water and hair samples. Percent recoveries for solutions containing Ag+ indicated that chemical interferences by selected anions (NO3−, Cl−, I−, Br− and citrate) or cations (Ni2+, Cu2+, Mg2+, Zn2+, Pb2+, Ca2+, Co2+, Hg2+, Na+ and Mn2+) in solution were minimal or non-existent.

Validation of an HPLC-FL Method for the Determination of Tepoxalin and its Major Metabolite in Horse Plasma

A sensitive, simple, and accurate high-performance liquid chromatographic (HPLC) method has been developed for the determination of tepoxalin, its major metabolite RWJ-20142 and the internal standard RWJ-20294 (Schering-Plough Co.) in horse plasma. The plasma samples (0.5 mL) were directly extracted with acetonitrile 0.9 mL; after high speed centrifugation to precipitate proteins 50 µL were injected into a HPLC. Separation was performed on a Gemini C18 column (250 mm × 4.6 mm i.d., 5 µm particles) with mobile phase A consisting of 0.01 M 1-octane-sulfonic acid in 0.01 M acetic acid aqueous solution and mobile phase B consisting of tetrahydrofuran, using an isocratic elution at 50% and 50% at 1.0 mL/min flow rate. Detection and quantitation were performed by fluorimetric detection at λex = 290 nm and λem = 440 nm. Detection and quantitation limits for tepoxalin and RWJ-20142 were 30 and 50 ng/mL, and 10 and 30 ng/mL, respectively. Recovery values for tepoxalin and RWJ-20142 were near 100%. The linear concentration range for tepoxalin and RWJ 20142 were 50‐5000 and 30‐5000 ng/mL, respectively. The validated reversed-phase HPLC-fluorescence detection method was used for determination of preliminary pharmacokinetic data of the drug in horse plasma.

Peroxidase‐Catalyzed Stabilization of 2,4‐Dichlorophenol in Alkali‐extracted Soils

Horseradish peroxidase- (HRP) mediated stabilization of phenolic contaminants is a topic of interest due to its potential for remediation of contaminated soils. This study evaluated the sorption of 2,4-dichlorophenol (DCP) and its HRP-mediated stabilization in two alkali-extracted soils. Alkali extraction reduced the soil organic matter (SOM) contents of the geomaterials and enriched the residual SOM with humin C. Sorption of DCP on these sorbents was complete within 1 d. However, most of the sorbed DCP was removed from the geomaterials by water and methanol, suggesting weak solute-sorbent interactions. The addition of HRP resulted in the generation of DCP polymerization products (DPP), which partitioned between the aqueous and solid phases. The DPP phase distribution was rapid and complete within 24 h. Between 70 and 90% of the added DCP was converted to DPP and up to 43% of the initial aqueous phase contaminant was transformed into a residue that was resistant to extraction with methanol. Bound residues of DPP increased with initial aqueous phase solute concentration and remained fairly constant after 7 d of contact. Contaminant stabilization was noted to be high in the humin-mineral geomaterial. Results illustrate that HRP may be effective in stabilizing phenolic contaminants in subsoils that are likely to contain SOM enriched in humin C.

A facile route to patterned epitaxial ZnO nanostructures by soft lithography

Combining two robust, facile, and low cost techniques—nanoimprint lithography and low temperature aqueous solution phase epitaxy of ZnO—enabled the fabrication of nanostructured single crystal surfaces. Various patterns were fabricated with sub-micron resolution, including an array of 70 nm diameter posts. The method requires no vacuum equipment and has a maximum process temperature of 110 °C.

Mesoporous silica hybrid membranes for precise size-exclusive separation of silver nanoparticles

One-dimensional (1D) nanomaterials have unique applications due to their inherent physical properties. In this study, hexagonally ordered mesoporous silica hybrid anodic alumina membranes (AAM) were synthesized using template-guided synthesis with a number of nonionic n-alkyl-oligo(ethylene oxide), Brij-type (C x EO y ), which are surfactants that have different molecular sizes and characteristics. The hexagonal mesoporous silicas are vertically aligned in the AAM channels with a predominantly columnar orientation. The hollow mesostructured silicas had tunable pore diameters varying from 3.7 to 5.1 nm. In this synthesis protocol, the surfactant molecular natures (corona/core features) are important for the controlled generation of ordered structures throughout AAM channels. The development of ultrafiltration membranes composed of silica mesostructures could be used effectively in separating silver nanoparticles (Ag NPs) in both aqueous and organic solution phases. This would be relevant to the production of well-defined Ag NPs with unique properties. To create a size-exclusive separation system of Ag NPs, we grafted hydrophobic trimethylsilyl (TMS) groups onto the inner pores of the mesoporous silica hybrid AAM. The immobilization of the TMS groups allowed the columnar mesoporous silica inside AAM to retain this inner pore order without distortion during the separation of solution-phase Ag NPs in organic solvents that may cause tortuous-pore membranes. Mesoporous TMS-silicas inside 1D AAM channels were applicable as a size-exclusive separation system to isolate organic solution-phase Ag NPs of uniform morphology and size.

Optically Active Lyotropic Chromonic Liquid Crystal Based on Green Perylene Bisimide

Recently, PBIs having ionic periphery have attracted much attention since they can form lyotropic chromonic liquid crystal-line (LCLC) phase in aqueous solution. In the LCLC phase, the molecules form a self-assembled columnar structure due to the π-π stacking of aromatic core and the hydrophilic interaction of ionic peripheries at water interface. A growing acceptance of the concept of chromonic phases and a wider recognition that they form a well-defined family of lyotropic liquid crystalline (LC) phases with variety of properties make the LCLCs distinct in almost every aspect from conventional lyotropic liquid cry-stals such as amphiphiles.

Simulation tool for variably saturated flow with comprehensive geochemical reactions in two- and three-dimensional domains

We present a software tool for simulations of flow and multi-component solute transport in two- and three-dimensional domains in combination with comprehensive intra-phase and inter-phase geochemistry. The software uses IPhreeqc as a reaction engine to the multi-purpose, multidimensional finite element solver COMSOL Multiphysics ® for flow and transport simulations. Here we used COMSOL to solve Richards’ equation for aqueous phase flow in variably saturated porous media. The coupling procedure presented is in principle applicable to any simulation of aqueous phase flow and solute transport in COMSOL. The coupling with IPhreeqc gives major advantages over COMSOL’s built-in reaction capabilities, i.e., the soil solution is speciated from its element composition according to thermodynamic mass action equations with ion activity corrections. State-of-the-art adsorption models such as surface complexation with diffuse double layer calculations are accessible. In addition, IPhreeqc provides a framework to integrate user-defined kinetic reactions with possible dependencies on solution speciation (i.e., pH, saturation indices, and ion activities), allowing for modelling of microbially mediated reactions. Extensive compilations of geochemical reactions and their parameterization are accessible through associated databases.

Fabrication of layered double hydroxide spheres through urea hydrolysis and mechanisms involved in the formation

The goal of this study is to prepare hydrotalcite pellets and validate their potential utility in catalysts and catalysts support. Hydrotalcite pellets were synthesized by urea hydrolysis. Urea hydrolysis can provide both carbonate as the intercalated anion and hydroxyl anions to form Mg–Al layered double hydroxide (LDH) with carbonate intercalation. Urea hydrolysis was also used to generate NH3 which plays a critical role in the process of synthesis hydrotalcite pellets. Mechanism of the formation hydrotalcite pellets was also discussed. The as-prepared samples were well characterized by X-ray diffraction, scanning electron microscopy, transmission electronic microscope, N2 adsorption/desorption, and Fourier transform infrared spectroscopy, respectively. The results revealed that the hydrotalcite pellets were well-crystallized and formed by self-assembly of hexagonal platelets LDHs. The present work suggests that it is possible to grow hydrotalcite pellets directly through one-step aqueous solution-phase chemical route under controlled conditions.

Preparation and Characterization of a Novel Polyamide Charged Mosaic Membrane

A novel composite charged mosaic membrane (CCMM) was prepared via interfacial polymerization (IP) of polyamine [poly(epichlorohydrin amine)] and trimesoyl chloride (TMC) on the polyethersulfone (PES) support. Fourier transform infrared spectroscopy (FT-IR), environmental scanning electron microscopy (ESEM), atomic force microscopy (AFM) and water contact angle analysis were applied to characterize the resulted CCMM. The FT-IR spectrum indicates that TMC reacts sufficiently with polyamine. ESEM and AFM pictures show that the IP process produces a dense selective layer on the support membrane. The water contact angle of the CCMM is smaller than that of the substrate membrane because of the cross-linked hydrophilic polyamine network. Several factors affecting the IP reaction and the performance of the CCMM, such as monomer concentration, reaction time, pH value of aqueous phase solution and post-treatment, were studied. The pure water flux of the optimized CCMM is 14.73 L·m −2·h −1·MPa −1 at the operating pressure of 0.4 MPa. The values of separation factor a for NaCl/PEG1000/water and MgCl 2/PEG1000/water are 11.89 and 9.96, respectively. These results demonstrate that CCMM is promising for the separation of low-molecular-weight organics from their salt aqueous solutions.

Visible-light Photocatalytic Activity of BiOCl/Bi3O4Cl Nanocomposites

The heterojunction structures of BiOCl/<TEX>$Bi_3O_4Cl$</TEX>, exhibiting considerable visible-light photocatalytic efficiency, were prepared by a simple wet-chemical process at ambient condition. The prepared nanocomposites were characterized by XRD, TEM, and UV-visible diffuse reflectance spectra. Under visible light (<TEX>${\lambda}\geq$</TEX>420 nm) irradiation, BiOCl/<TEX>$Bi_3O_4Cl$</TEX> exhibited an enhanced photocatalytic activity in decomposing 2-propanol (IP) in gas phase and salicylic acid (SA) in aqueous solution, whereas the bare BiOCl and <TEX>$Bi_3O_4Cl$</TEX> showed negligible activities. It is deduced that the remarkable visible-light photocatalytic activity of the BiOCl/<TEX>$Bi_3O_4Cl$</TEX> originates from the hole <TEX>$(h^+)$</TEX> transfer between VB of the <TEX>$Bi_3O_4Cl$</TEX> and BiOCl semiconductors.

On-line coupling of counter-current chromatography and macroporous resin chromatography for continuous isolation of arctiin from the fruit of Arctium lappa L.

In this work, we have developed a novel hybrid two-dimensional counter-current chromatography and liquid chromatography (2D CCC × LC) system for the continuous purification of arctiin from crude extract of Arctium lappa. The first dimensional CCC column has been designed to fractionalize crude complex extract into pure arctiin effluent using a one-component organic/salt-containing system, and the second dimensional LC column has been packed with macroporous resin for on-line adsorption, desalination and desorption of arctiin which was effluent purified from the first CCC dimension. Thus, the crude arctiin mixture has been purified efficiently and conveniently by on-line CCC × LC in spite of the use of a salt-containing solvent system in CCC separation. As a result, high purity (more than 97%) of arctiin has been isolated by repeated injections both using the ethyl acetate–8% sodium chloride aqueous solution and butanol–1% sodium chloride aqueous solution. By contrast with the traditional CCC processes using multi-component organic/aqueous solvent systems, the present on-line CCC × LC process only used a one-component organic solvent and thus the solvent is easier to recover and regenerate. All of used solvents such as ethyl acetate, n-butanol and NaCl aqueous solution are low toxicity and environment-friendly. Moreover, the lower phase of salt-containing aqueous solution used as mobile phase, only contained minor organic solvent, which will save much organic solvent in continuous separation. In summary, our results indicated that the on-line hybrid 2D CCC × LC system using one-component organic/salt-containing aqueous solution is very promising and powerful tool for high-throughput purification of arctiin from fruits of A. lappa.

Preparation of porous silk fibroin microparticles by a water‐in‐oil emulsification‐diffusion method

AbstractPorous silk fibroin (SF) microparticles were prepared by a simple one‐step water‐in‐oil emulsification‐diffusion method. Aqueous SF solution and organic phase solvent were used as water and oil phases, respectively. Four organic solvents with different water solubility were studied, i.e., ethyl acetate, diethyl ether, dichloromethane, and chloroform. Influences of organic phase solvent, water/oil volume ratio, and SF concentration on SF microparticle characteristics were investigated. It was found that shape of the SF microparticles depended upon the type of organic phase solvent. The SF microparticles with hollow or bowl‐like shape were fabricated when organic solvents with higher water solubility, which are ethyl acetate and diethyl ether, were used as the continuous oil phase. While using organic solvents with lower water solubility, i.e., dichloromethane and chloroform resulted in the spherical shape SF microspheres. The water/oil volume ratios and the SF concentrations did not affect on the bowl‐like and spherical shapes of SF microparticles. Results from scanning electron microscope shows that all the SF microparticle matrices were porous structures. Using ethyl acetate and diethyl ether as the oil phase gave larger SF microparticle sizes than using dichloromethane and chloroform. The influences of water/oil volume ratio and the SF concentration showed slightly effect on the sizes of SF microparticles. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

A New Approach of Synthesis of Micro/Nanoscale HgS Spheres

Micro/nanoscale spherical HgS has been prepared by reaction of Na 2 [Hg(HL) 2 (H 2 O) 2 ]; 1:2 (M:L) chelate complex with alkaline solution of thiourea in aqueous solution phase. The metal chelate complex was prepared by reaction of Hg(II) ions with 2-hydroxy-1-(1-hydroxy-2-naphthylazo)-6-nitronaphthalene-4-sulphonic acid sodium salt; eriochrome black T (EBT, NaH2L) in alkaline medium. The chelate complex precursor thus prepared was characterized by various physico-chemical and spectral techniques for structure determination. The spherical HgS material was characterized by scanning electron microscopy and energy dispersive X-ray analysis to determine morphology and chemical composition. The optical property was determined by UV-Vis spectrum. A possible formation mechanism has also been discussed in this article.

Magnetic Self-Orientation of Lyotropic Hexagonal Phases Based on Long Chain Alkanoic (Fatty) Acids

It is presently shown that long chain (C14, C16, and C18) alkanoic (saturated fatty) acids can form magnetically oriented hexagonal phases in aqueous concentrated solutions in mixtures with tetrabutylammonium (TBAOH) as the counterion. The hexagonal phase occurred for a molar ratio, alkanoic acid/TBAOH, higher than 1, i.e., for an excess of fatty acid. The hexagonal phase melted to an isotropic phase (micelles) upon heating at a given temperature depending on the alkyl chain length. The self-orientation of the hexagonal phase occurred upon cooling from the "high-temperature" isotropic phase within the magnetic field. The long axis of the hexagonal phase was shown to self-orient parallel to the magnetic field as evidenced by deuterium solid-state NMR. This finding is expected to be of interest in the field of structural biology and materials chemistry for the synthesis of oriented materials.

Density Functional Theory Calculations of the Molecular Force Field ofl-Ascorbic Acid, Vitamin C

We have studied L-ascorbic acid and characterized it by infrared spectroscopy in solid and aqueous solution phases. The density functional theory (DFT) method together with Pople's basis set show that three stable molecules for the compound have been theoretically determined in the gas phase, and that an average of only two more stable conformations are present in the solid phase, as it was experimentally observed. The harmonic vibrational wavenumbers for the optimized geometries of both structures were calculated at B3LYP/6-31G*and B3LYP/6-311++G** levels at the proximity of the isolated molecule. For a complete assignment of the vibrational spectra in the compound solid and aqueous solution phases, DFT calculations were combined with Pulay's scaled quantum mechanics force field methodology in order to fit the theoretical wavenumber values to the experimental ones. In this way, a complete assignment of all the observed bands in the infrared spectrum for l-ascorbic acid was performed. The natural bond orbital study reveals the characteristics of the electronic delocalization of the three structures while the corresponding topological properties of electronic charge density are analyzed by employing Bader's atoms-in-molecules theory.

Hydrogen Bonding and Compartmentalization of Water in Supercooled and Frozen Aqueous Acetone Solutions

Temperature ramp Fourier transform infrared (FTIR) microspectroscopy was utilized to examine hydrogen bonding (HB) in and crystallization of supercooled aqueous acetone solutions. We showed that temperature and concentration-dependent transitions between different water populations, representing distinct HB organization, played very significant roles in ice crystallization and formation of distinct thermodynamic phases in supercooled aqueous solutions. At cryogenic temperatures, mainly three different coexisting thermodynamic phases were identified: a hexagonal ice phase, which exhibited linear planar growth with supercooling; a low water content supercooled solution rich in water monomers and dimers, which froze at lower temperatures as a result of a significant increase in HB networking; and a high water content frozen solution. We show that spectroscopic analysis water in polar solutions at cryogenic temperatures present a unique platform to explore the freezing/melting/vitrification behavior of water.

Synthesis of monodispersed cubic magnetite particles through the addition of small amount of Fe 3+ into Fe(OH) 2 suspension

Magnetite particles were synthesized through a process including dissolution of Fe(OH) 2 and precipitation of an oxidized phase in aqueous solution. The Fe 3+ ion was added at the beginning of the synthesis to accelerate the formation of magnetite, control the particle size and improve the monodispersibility. It was found that the addition of Fe 3+ ion affected the nucleation and the formation of magnetite particles significantly. Magnetite nanoparticles with small particle size and narrow size distribution were obtained. Furthermore, high magnetic properties were obtained in small particle size. The particle size and magnetic properties increased through the increase of Fe 2+/Fe 3+ ratio.