Anodic oxide formation on aluminium-terbium alloys

Aluminium terbium alloys were prepared by simultaneous thermal evaporation resulting in a thin film library covering a 5 to 25 at.% Tb compositional spread. Synchrotron x-ray diffraction (XRD) proves all of the alloys to be amorphous. Scanning electron microscopy (SEM) measurements reveal the structural changes upon increase in Tb content with the formation of small, Tb-rich segregations right before a drastic change in morphology around 25 at.% Tb. Anodic oxides were formed systematically in cyclic voltammograms using scanning droplet cell microscopy. Coulometric analysis revealed a linear thickness over formation potential behaviour with film formation factors ranging from 1.2 nm V^?1 (5 at.% Tb) to 1.6 nm V^?1 (25 % Tb). Electrochemical impedance spectroscopy was performed for each incremental oxidation step resulting in a linear relation between inverse capacity and formation potential with dielectric constants ranging from 8 (5 at.% Tb) to 16 (25 at.% Tb).     

Hydrogel-based flexible micro-reference electrodes for use in alkaline and neutral pH solutions

Two types of nonbreakable, flexible micro-reference electrodes filled with gel-electrolytes were prepared for use in solutions with alkaline and neutral pH. The electrodes are intended for electrochemical measurements, in which chloride-free conditions are important. Due to the flexible, bendable construction of the electrodes, electrochemical experiments at locations difficult to access with common reference electrodes are enabled. Hg|HgO-type electrodes were prepared from amalgamated Au wires, followed by oxidation of the amalgam, which is mounted in a PTFE tube filled with 0.1M NaOH solution immobilized in a PAA-g-PEO gel. The potential of this type of electrode was found to be 0.162?±?0.002 V (SHE) at room temperature. Cu|CuSO₄ electrodes, consisting of a Cu wire immersed in a saturated CuSO₄ solution jellied with gelatin, showed a stable open-circuit potential of 0.312?±?0.001 V (SHE). Further characterization of the electrodes was performed in terms of electrochemical impedance spectroscopy and micro-polarization measurements. As an alternative to the flexible electrodes, rigid electrodes in glass enclosure were fabricated in analogy to the flexible-type electrodes.     

Simultaneous quantification of Echinacea species, Flos Lonicerae, Radix Scutellaria and Fructus Forsythiae combinations by rapid resolution liquid chromatography

Echinacea angustifolia and E. purpurea are commonly used in North America for their anti-bacterial effects. Flos Lonicerae, Radix Scutellaria and Fructus Forsythiae are traditional Chinese medicinal herbs commonly used for the treatment of complaints such as pneumonia, acute upper respiratory tract infection, and acute bronchitis. A reproducible, simple, and reliable rapid resolution liquid chromatographic (RRLC) method has been developed to analyze extracts of products formulated containing E. angustifolia, E. purpurea, Flos Lonicerae, Radix Scutellariae and Fructus Forsythiae simultaneously in one run in less than 6 minutes. The method uses a C18-HST column, a mobile phase consisting of 0.1% aqueous phosphoric acid solution and acetonitrile, and UV detection at 327 nm and 229 nm. A stability test was performed that revealed that chlorogenic acid is more stable in acidic pH, and hence it is best to keep the extract of E. augustifolia, E. purpurea, Flos Lonicerae, Radix Scutellariae and Fructus Forsythiae in mild acidic conditions at approximately pH 5.     

Adsorption of indigo carmine from aqueous solution using coal fly ash and zeolite from fly ash

Coal fly ash, a waste generated at the Figueira coal-fired electric power plant located in Brazil, was used to synthesize zeolite by hydrothermal treatment with NaOH solution at 100 °C for 24 h. The fly ash (FA) and this synthesized zeolite (ZM) that was characterized predominantly as hydroxy-sodalite were used as adsorbents for anionic dye indigo carmine from aqueous solutions. The samples were analyzed by instrumental neutron activation analysis (INAA) for the determination of As, Co, Fe, La, Mo, Na, Sb, Sc, Sm, Th, U and Zn. Effects of contact time and initial dye concentration were evaluated in the adsorption processes. The kinetics studies indicated that the adsorption followed the pseudo-second order kinetics and that surface adsorption and intraparticle diffusion were involved in the adsorption mechanism for both the adsorbents. The Langmuir isotherm model provided the best correlation of the experimental data. The maximum adsorption capacity was found to be 1.48 mg L⁻¹ for FA and 1.23 mg L⁻¹ for ZM. Laboratory leaching and solubilization tests conducted to classify this ZM as if was a waste residue according to the Brazilian regulation classified it as a residue non-hazardous and non-inert.     

A DFT comparison of the neutral and cationic Heck pathways

The two distinct mechanistic pathways of the Heck reaction, cationic and neutral, are characterized computationally using DFT calculations with corrections for solvation and dispersion. The selectivity in each type of reaction is discussed in terms of the detailed reaction paths, and the two types are compared to each other. The geometries and energies of the selectivity-determining transitions states are analyzed in detail.     

Response surface methodology for optimization of cyanamide analysis by in situ derivatization and dispersive liquid–liquid microextraction

Cyanamide is widely used for agricultural purposes; therefore, its residues can be found in water. A new method was developed for its quantification using in situ derivatization with 2,6‐dimethyl‐4‐quinolinecarboxylic acid N‐hydroxysuccinimide ester followed by dispersive liquid–liquid microextraction (DLLME) and high‐performance liquid chromatography/fluorescence analysis. Multivariate chemometric techniques were successfully used to obtain the optimum conditions for direct derivatization and DLLME extraction. Derivatization parameters and DLLME extraction conditions were optimized by a two‐step design, 2^k factorial design for screening, and central composite design for optimization. Best derivatization conditions were addition of 600 μL of derivatizing reagent, a temperature of 4 ºC, and pH 8.5, whereas for optimum extraction 800 μL of solvent, 30% NaCl conc. w/v, and pH 3.8 were chosen. The analytical performance of the method for routine analysis was evaluated. Excellent linearity was achieved from 10 to 200 µg L⁻¹ with a correlation factor of 0.9996. Precision ranged from 3.5% to 5.5% for intraday assays and 8.5% to 8.6% for interday assays. The mean recoveries performed on water from different origins (ground, river, sea, tap, and mineral) at three levels of concentration (20, 75, and 200 µg L⁻¹) ranged from 90.2% to 110.2%. Copyright © 2014 John Wiley & Sons, Ltd.     

Solid-phase based synthesis of biologically promising triazolyl aminoacyl (peptidyl) penicillins

An efficient and versatile methodology for the preparation of valuable triazolyl aminoacyl (peptidyl) penicillins is described. Solid-phase Cu(I)-catalyzed Hüisgen 1,3-dipolar cycloaddition was used as the key step showing general applicability and excellent regioselectivity either with CuI or [Cu(CH₃CN)₄]PF₆ as Cu(I) source.     

Quadruple domino organocatalysis: an asymmetric aza-michael/michael/michael/aldol reaction sequence leading to tetracyclic indole structures with six stereocenters

Quadruple domino/Wittig-one pot: An organocatalytic, asymmetric, three-component quadruple cascade, which leads to tetracyclic double-annulated indole derivatives, is described. The domino products were further derivatized by aldehyde olefination under one-pot conditions to obtain complex isoindolo[2,?1-a]indole derivatives bearing six stereogenic centers in a highly stereoselective fashion.     

Fourth ANKA and KNMF User Meeting 2012

On October 10–11, 2012, the ANKA synchrotron radiation facility and the Karlsruhe NanoMicro Facility (KNMF), both user research facilities at the Karlsruhe Institute of Technology (KIT) in Germany, hosted their fourth joint annual user meeting at the Ettlingen Castle. In the extraordinary ambiance of the baroque palace, the ANKA and KNMF directorates (represented by Clemens Heske and Jürgen Mohr, respectively) welcomed almost 200 participants representing universities, research facilities, and companies from 10 different countries. The meeting was kicked off by KIT Chief Science Officer Volker Saile, who emphasized the positive developments and increase in user numbers at both facilities.     

Direct synthesis of inverse hexagonally ordered diblock copolymer/polyoxometalate nanocomposite films

Nanostructured inverse hexagonal polyoxometalate composite films were cast directly from solution using poly(butadiene-block-2-(dimethylamino)ethyl methacrylate) (PB-b-PDMAEMA) diblock copolymers as structure directing agents for phosphomolybdic acid (H(3)[PMo(12)O(40)], H(3)PMo). H(3)PMo units are selectively incorporated into the PDMAEMA domains due to electrostatic interactions between protonated PDMAEMA and PMo(3-) anions. Long solvophilic PB chains stabilized the PDMAEMA/H(3)PMo aggregates in solution and reliably prevented macrophase separation. The choice of solvent is crucial. It appears that all three components, both blocks of the diblock copolymer as well as H(3)PMo, have to be soluble in the same solvent which turned out to be tetrahydrofuran, THF. Evaporation induced self-assembly resulted in highly ordered inverse hexagonal nanocomposite films as observed from transmission electron microscopy and small-angle X-ray scattering. This one-pot synthesis may represent a generally applicable strategy for integrating polyoxometalates into functional architectures and devices.