428 results match your criteria: "Clausthal University of Technology[Affiliation]"

The centrosymmetric binuclear complex cation of the title compound, [Cu(CHNO)(CHN)](NO)·CHNO·8HO, is composed of a Cu atom with a distorted trigonal-bipyramidal coordination environment defined by four N atoms from two bidentate 1,10-phenanthroline ligands and one oxygen atom from one-half of the monodentate ,'-(1,4-phenyl-enedicarbon-yl)diglycinate anion. The asymmetric unit is completed by one-half of the ,'-(1,4-phenyl-enedicarbon-yl)diglycine solvent mol-ecule, which is located on a centre of inversion, by one nitrate counter-anion and four water mol-ecules. In the crystal, the cationic complexes are linked inter-molecular π-π stacking and through lone-pair⋯π inter-actions involving the ,'-(1,4-phenyl-enedicarbon-yl)diglycinate anion and the phenanthroline ligands.

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The transition towards a bio-based world is a challenging undertaking. This perspective paper, from an engineering point of view, aims to provide an overview of existing projects and academic disciplines highlighting the potential benefit of increased interdisciplinary exchanges. Furthermore, the current utilization of biomass to produce biogas is discussed, including an economic assessment, showing the need for new strategies of biomass valorization.

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Oxygen-depolarized cathodes are a novel concept to be used in chlor-alkali electrolysis in order to generate significant energy savings. In these porous gas diffusion electrodes, hydrophilic and catalytically active microsized silver grains and a hydrophobic polytetrafluoroethylene cobweb structure are combined to obtain the optimum amount of three-phase boundaries between the highly alkaline electrolyte and the oxygen gas phase to achieve high current densities. However, the direct correlation between specific electrode structure and electrochemical performance is difficult.

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Diels-Alder reaction of 2-, 3- and 4-(phenylethynyl)quinolines and tetraphenylcyclopentadienone gave three regioisomeric 2,3,4,5,6-pentaphenyl-1-(quinolin-2-yl, -3-yl, and -4-yl)benzenes. Restricted rotation of the 3-yl and 4-yl substituted derivatives is observed between the central core and the substituents, resulting in propeller-shaped molecules. Likewise, 1,2-diquinolinyl-3,4,5,6-tetraphenylbenzenes with 3-yl,3-yl and 3-yl,4-yl connectivity were prepared.

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Semi-batch emulsion polymerizations of vinylidene fluoride (VDF) are reported. The molar mass control is achieved via iodine transfer polymerization (ITP) using IC₄F₈I as chain transfer agent. Polymerizations carried out at 75 °C and pressures ranging from 10 to 30 bar result in low dispersity polymers with respect to the molar mass distribution (MMD).

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Objective: A synthetic pathway to γ-hydroxy-α-(arylmethyl)carboxylic acids starting from α-angelica lactone and γ-butyrolactone was investigated. These γ-hydroxycarboxylic acids resemble structural motifs of lactic acid and amino acids. The possibility of cocondensation with lactic acid towards functionalized poly(lactic acid)s was analyzed.

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Catalytic Reactivation of Industrial Oxygen Depolarized Cathodes by in situ Generation of Atomic Hydrogen.

ChemSusChem

June 2019

Analytical Chemistry-Center for Electrochemical Sciences (CES), Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Universitätsstr. 150, 44780, Bochum, Germany.

Electrocatalytically active materials on the industrial as well as on the laboratory scale may suffer from chemical instability during operation, air exposure, or storage in the electrolyte. A strategy to recover the loss of electrocatalytic activity is presented. Oxygen-depolarized cathodes (ODC), analogous to those that are utilized in industrial brine electrolysis, are analyzed: the catalytic activity of the electrodes upon storage (4 weeks) under industrial process conditions (30 wt % NaOH, without operation) diminishes.

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Developing functional materials via electroless deposition, without the need of external energy is a fascinating concept. Electroless deposition can be subcategorized into galvanic displacement reaction, disproportionation reaction, and deposition in presence of reducing agents. Galvanic displacement reaction is a spontaneous reduction process wherein the redox potentials of the metal/metal ion in the electrolyte govern the thermodynamic feasibility of the process.

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Bone-inspired enhanced fracture toughness of de novo fiber reinforced composites.

Sci Rep

February 2019

Department of Mechanical Engineering, Politecnico di Milano, via G. La Masa 1, 20156, Milano, Italy.

Amplification in toughness and balance with stiffness and strength are fundamental characteristics of biological structural composites, and a long sought-after objective for engineering design. Nature achieves these properties through a combination of multiscale key features. Yet, emulating all these features into synthetic de novo materials is rather challenging.

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A suitable balance of convective and diffusive transport of small molecules contained in the liquid phase of a drying latex film leads to auto-stratification and to functionally graded films. Differing from blends of latex particles, which may also experience drying-induced segregation, small molecules retain their mobility after the particles have touched and have formed an elastically coupled network. The use of a thickener, which turns the dispersion into a weak gel and prevents the free flow of particles, is compatible with this approach (and even advantageous).

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The sydnone imines (5-benzoylimino)-3-(2-methoxyphenyl)-sydnone imine and molsidomine were deprotonated at C4 to give sydnone imine anions which can be represented as anionic N-heterocyclic carbenes, respectively. Trapping reactions with sulfur gave unstable sydnone imine sulfides which were stabilized by the formation of methyl thioethers, methyl sulfoxides, gold complexes [(PPh)Au-S-sydnone imine] and a bis(ligand) mercury(ii) complex. The latter possesses a tetrahedral coordination of the mercury central atom to the sulfur atoms with the N6 nitrogen atoms coordinating as neutral ligands.

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Transport mechanisms in structurally ordered piezoelectric CaTaGaSiO (CTGS) single crystals are studied in the temperature range of 1000-1300 °C by application of the isotope O as a tracer and subsequent analysis of diffusion profiles of this isotope using secondary ion mass spectrometry (SIMS). Determined oxygen self-diffusion coefficients enable calculation of oxygen ion contribution to the total conductivity, which is shown to be small. Since very low contributions of the cations have to be expected, the total conductivity must be dominated by electron transport.

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Background: Since malaria parasites highly depend on ribose 5-phosphate for DNA and RNA synthesis and on NADPH as a source of reducing equivalents, the pentose phosphate pathway (PPP) is considered an excellent anti-malarial drug target. In Plasmodium, a bifunctional enzyme named glucose 6-phosphate dehydrogenase 6-phosphogluconolactonase (GluPho) catalyzes the first two steps of the PPP. PfGluPho has been shown to be essential for the growth of blood stage Plasmodium falciparum parasites.

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The photoinduced curing of a light-sensitive varnish was followed, based on a change of the film's shear modulus, G, as determined with a quartz crystal microbalance (QCM). The film thickness was in the range of a few hundred nanometers. Both the storage modulus, G', and the loss modulus, G″, were obtained.

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Metal Organic Frameworks (MOFs) and ultrasound: A review.

Ultrason Sonochem

April 2019

National Technical University of Athens, School of Chemical Engineering, 9 Heroon Polytechniou, 15773 Zografou, Athens, Greece; Clausthal Centre of Materials Technology, Leibnizstr. 9, 38678 Clausthal-Zell., Germany; Institute of Energy Research and Phys. Technologies, Clausthal University of Techno

Metal-organic frameworks (MOFs) have received a lot of attention due to their unique properties and abundant functionalities. Permanent porosity and high surface area are just a few traits that have made them attractive to researchers. They can be prepared as task-specific materials by exploiting the functional group variety and tuning their size and geometry.

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Polymer electrolyte membranes (PEM) prepared by radiation-induced graft copolymerization are investigated. For this purpose, commercial poly(ethylene-alt-tetrafluoroethylene) (ETFE) films were activated by electron beam treatment and subsequently grafted with the monomers glycidyl methacrylate (GMA), hydroxyethyl methacrylate (HEMA) and ,'-methylenebis(acrylamide) (MBAA) as crosslinker. The target is to achieve a high degree of grafting () and high proton conductivity.

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Liquid-liquid phase separation is mainly dependent on temperature and composition. Electric fields have also been shown to influence demixing of binary liquid mixtures. However, a puzzling behavior that remains elusive is the electric field-induced phase separation in ion-containing solvents at low voltages, as predicted by Tsori and Leibler.

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6-Chloropurine and 2,6-dichloropurine were reacted with N1-substituted imidazoles to give purin-6-yl substituted imidazolium salts, respectively. Deprotonation of the 1-methylimidazolium derivative resulted in the formation of the corresponding stable conjugated mesomeric betaine, whereas the 1-phenyl,- 1-vinyl- and 1-(2-hydroxyethyl) derivatives proved to be unstable. In situ generation of the mesomeric betaines by caesium carbonate in the presence of sulfur and selenium, however, gave the thiones and the selenones of the tautomeric purine-substituted imidazol-2-ylidene, respectively.

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Li permeation through ultrathin Cr, Si and C layers and interfaces is of interest in the optimization of lithium ion batteries with respect to the control of Li flux. Twenty-one LiNbO3 layers (9 nm), which serve as solid state Li reservoirs, were sputter deposited in an alternating sequence of enriched 6Li or 7Li isotope fractions spaced with (8 nm) thin Cr, Si and C layers. The Li isotope contrast was used to measure Li permeation using depth profiling by secondary ion mass spectrometry and neutron reflectometry on a nanometer scale.

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Local Activities of Hydroxide and Water Determine the Operation of Silver-Based Oxygen Depolarized Cathodes.

Angew Chem Int Ed Engl

September 2018

Analytical Chemistry-Center for Electrochemical Sciences (CES), Ruhr-Universität Bochum, Universitätsstr. 150, 44780, Bochum, Germany.

Local ion activity changes in close proximity to the surface of an oxygen depolarized cathode (ODC) were measured by scanning electrochemical microscopy (SECM). While the operating ODC produces OH ions and consumes O and H O through the electrocatalytic oxygen reduction reaction (ORR), local changes in the activity of OH ions and H O are detected by means of a positioned Pt microelectrode serving as an SECM tip. Sensing at the Pt tip is based on the pH-dependent reduction of PtO and obviates the need for prior electrode modification steps.

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Interactions between Lithium, an Ionic Liquid, and Si(111) Surfaces Studied by X-ray Photoelectron Spectroscopy.

J Phys Chem Lett

August 2018

Institute of Electrochemistry , Clausthal University of Technology, Arnold-Sommerfeld-Strasse 6 , 38678 Clausthal-Zellerfeld , Germany.

Investigations of the solid-electrolyte interphase formation on a silicon anode are of great interest for future lithium-ion batteries. We have studied the interactions of the ionic liquid 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl) amide ([OMIm]TfN) and of lithium with Si(111) surfaces on a molecular level by X-ray photoelectron spectroscopy. The interaction of Li with [OMIm]TfN on Si(111) results in the decomposition of both the cation and the anion and the intercalation of lithium.

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Nanoparticles are coated in-flight with a plasma-enhanced chemical vapor deposition (PECVD) process at ambient or elevated temperatures (up to 300 °C). Two silicon precursors, tetraethyl orthosilicate (TEOS) and hexamethyldisiloxane (HMDSO), are used to produce inorganic silica or silica-organic shells on Pt, Au and TiO₂ particles. The morphology of the coated particles is examined with transmission electron microscopy (TEM) and the chemical composition is studied with Fourier-transform infrared spectroscopy (FTIR), Energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS).

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Melting presents one of the most prominent phenomena in condensed matter science. Its microscopic understanding, however, is still fragmented, ranging from simplistic theory to the observation of melting point depressions. Here, a multimethod experimental approach is combined with computational simulation to study the microscopic mechanism of melting between these two extremes.

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In the present paper, deterministic as well as first- and second-order probabilistic biosphere modeling approaches are compared. Furthermore, the sensitivity of the influence of the probability distribution function shape (empirical distribution functions and fitted lognormal probability functions) representing the aleatory uncertainty (also called variability) of a radioecological model parameter as well as the role of interacting parameters are studied. Differences in the shape of the output distributions for the biosphere dose conversion factor from first-order Monte Carlo uncertainty analysis using empirical and fitted lognormal distribution functions for input parameters suggest that a lognormal approximation is possibly not always an adequate representation of the aleatory uncertainty of a radioecological parameter.

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Activation of the NF-κB pathway alters the phenotype of MSCs in the tracheal aspirates of preterm infants with severe BPD.

Am J Physiol Lung Cell Mol Physiol

July 2018

Division of Neonatology, University Children's Hospital, Perinatal Center, Ludwig-Maximilians-University, Campus Grosshadern, Munich , Germany.

Mesenchymal stromal cells (MSCs) are released into the airways of preterm infants following lung injury. These cells display a proinflammatory phenotype and are associated with development of severe bronchopulmonary dysplasia (BPD). We aimed to characterize the functional properties of MSCs obtained from tracheal aspirates of 50 preterm infants who required invasive ventilation.

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