Phase boundary propagation in large LiFePO4 single crystals on delithiation

Large single crystals of LiFePO(4) have been chemically delithiated. The relevance of chemical oxidation in comparison with electrochemical delithiation is discussed. Analyses of the Li content and profiles were done by electron energy loss spectroscopy and secondary ion mass spectrometry. The propagation of the FePO(4) phase growing on the surface of the large single crystal was followed by in situ optical microscopy as a function of time. The kinetics were evaluated in terms of linear irreversible thermodynamics and found to be characterized by an induction period followed by parabolic growth behavior of the FePO(4) phase indicating transport control. The growth rate was shown to depend on the crystallographic orientation. Scanning electron microscopy images showed cracks and a high porosity of the FePO(4) layer due to the significant changes in the molar volumes. The transport was found to be greatly enhanced by the porosity and crack formation and hence greatly enhanced over pure bulk transport, a result which is supposed to be very relevant for battery research if coarse-grained powder is used.     

The efficient synthesis of amphiphilic oximes of galactose and glucosamine

New amphiphilic oximes of galactose and glucosamine have been synthesized and characterized. The oxime functionality has been introduced to the first and sixth positions of a nonionic surfactant, consisting of a sugar polar head and a lipophilic side chain. The compounds are soluble in pyridine and sparingly soluble in other polar organic solvents and water.     

Microwave-assisted synthesis of amphiphilic spin probes

New amphiphilic nitroxide spin probes have been synthesized. The key reaction is based on microwave-assisted epoxide ring opening with amines as nucleophiles using calcium trifluoromethanesulfonate as a catalyst. High yields, in short reaction times, were obtained without any detectable nitroxide decomposition.     

Light trapping in amorphous silicon solar cells with periodic grating structures

We report on the design of amorphous silicon solar cells with the periodic grating structures. It is a combination of an anti-reflection structure and the metallic reflection grating. Optical coupling and light trapping in thin-film solar cells are studied numerically using the Rigorous Coupled Wave Analysis enhanced by the Modal Transmission Line theory. The impact of the structure parameters of the gratings is investigated. The results revealed that within the incident angles of ? 40^° to + 40^° the reflectivity of the cell with a period of 0.5 μm, a filling factor of 0.1 and a groove depth of 0.4 μm is 4%–22.7% in the wavelength range of 0.3–0.6 μm and 1%–20.8% in the wavelength range of 0.6–0.84 μm, the absorption enhancement of the a-Si layer is 0.4%–10.8% and 20%–385%, respectively.     

Magnetic properties of ErxY1−xF3 solid solutions

The Er_xY_1−xF₃ (x=0.1, 0.2, 0.7, 0.9, 1) solid solutions were synthesized and characterized by X-ray powder diffraction and magnetic measurements. The crystal structure refinements done by the Rietveld profile method show that no significant change of the structure parameters with the erbium concentration occurs. On the basis of DC susceptibility measurements in the 2-300 K range the lowest four crystal field levels have been determined, giving the ground level magnetic moment value of 6.7 μ_B. Results of M(H) studies point to the presence of complex exchange interactions between erbium ions.     

Heat transfer from laminar flow through cylindrical tubes

Zusammenfassung Die Differentialgleichung für Wärmeleitung in einer durch ein zylindrisches Rohr strömenden Flüssigkeit, die wie bekannt schon öfters behandelt wurde, wird in der vorliegenden Arbeit mittels der konfluenten hypergeometrischen Funktion gelöst. Bei der Berechnung des ersten Eigenwertes wird von den neulich herausgegebenen Tafeln Gebrauch gemacht.     

Multifunctional superhydrophobic/oleophobic and flame-retardant cellulose fibres with improved ice-releasing properties and passive antibacterial activity prepared via the sol–gel method

In this research, a two-component sol–gel inorganic–organic hybrid coating was prepared on a cotton fibre surface. An equimolar sol mixture of the precursors 1H,1H,2H,2H-perfluorooctyltriethoxysilane (SiF) and P,P-diphenyl-N-(3-(trimethoxysilyl)propyl) phosphinic amide (SiP) was applied to cotton fabric samples using the pad-dry-cure method. The surfaces of the untreated and coated cotton fibres were characterised using scanning electron microscopy, Fourier transform-infrared spectroscopy, X-ray photoelectron spectroscopy, and time-of-flight-secondary ion mass spectrometry. The functional properties of the coated cotton fabric samples were investigated using static contact angle measurements with water and n-hexadecane, the ice-releasing test, antibacterial testing against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli, thermogravimetric analysis in an air atmosphere, and vertical flammability tests. The results reveal the formation of a nanocomposite two-component inorganic–organic hybrid polymer network that is homogenously distributed over the cotton fibre surface. The presence of the SiP component in the two-component inorganic–organic hybrid coating did not hinder the functional properties imparted by the presence of the SiF component and vice versa, illustrating their compatibility. The cooperative action of the SiF and SiP components in the two-component coating provided the cotton fabric with exceptional multifunctionality, including simultaneous superhydrophobicity and high oleophobicity, passive antibacterial activity, and improved thermo-oxidative stability.     

Supramolecular Stabilization of Metastable Tautomers in Solution and the Solid State

This work presents a successful application of a recently reported supramolecular strategy for stabilization of metastable tautomers in cocrystals to monocomponent, non‐heterocyclic, tautomeric solids. Quantum‐chemical computations and solution studies show that the investigated Schiff base molecule, derived from 3‐methoxysalicylaldehyde and 2‐amino‐3‐hydroxypyridine ( ap ), is far more stable as the enol tautomer. In the solid state, however, in all three obtained polymorphic forms it exists solely as the keto tautomer, in each case stabilized by an unexpected hydrogen‐bonding pattern. Computations have shown that hydrogen bonding of the investigated Schiff base with suitable molecules shifts the tautomeric equilibrium to the less stable keto form. The extremes to which supramolecular stabilization can lead are demonstrated by the two polymorphs of molecular complexes of the Schiff base with ap . The molecules of both constituents of molecular complexes are present as metastable tautomers (keto anion and protonated pyridine, respectively), which stabilize each other through a very strong hydrogen bond. All the obtained solid forms proved stable in various solid‐state and solvent‐mediated methods used to establish their relative thermodynamic stabilities and possible interconversion conditions.     

Intercalation of a Heterocyclic Ligand between Quartets in a G-Rich Tetrahelical Structure

YES G-rich oligonucleotide VK2 folds into an AGCGA-quadruplex tetrahelical structure distinct and significantly different from G-quadruplexes, even though it contains four G₃ tracts. Herein, a bis-quinolinium ligand 360A with high affinity for G-quadruplex structures and selective telomerase inhibition is shown to strongly bind to VK2. Upon binding, 360A does not induce a conformational switch from VK2 to an expected G-quadruplex. In contrast, NMR structural study revealed formation of a well-defined VK2–360A complex with a 1:1 binding stoichiometry, in which 360A intercalates between GAGA- and GCGC-quartets in the central cavity of VK2. This is the first high-resolution structure of a G-quadruplex ligand intercalating into a G-rich tetrahelical fold. This unique mode of ligand binding into tetrahelical DNA architecture offers insights into the stabilization of an AGCGA-quadruplex by a heterocyclic ligand and provides guidelines for rational design of novel VK2 binding molecules with selectivity for different DNA secondary structures.     

XPS study of the deposited Ti layer in a magnetron-type sputter ion pump

X-ray photoelectron spectroscopy (XPS) was used to study the surface chemical composition of the anode deposits in a miniature magnetron ion pump. The pump was mounted on an UHV system with the ultimate pressure of 1 × 10⁻⁹ mbar. A stable discharge was established in the nitrogen atmosphere with some traces of CO at about 10⁻⁷ mbar. The cathode was made of pure titanium. The sputtered titanium atoms deposited on the anode, where they reacted with gases to form a film of titanium compounds. The thickness of the deposited titanium layer on the anode was about 100 nm. The results from XPS investigations indicate that active gases such as O₂ and N₂ react with Ti forming TiO₂ and TiN. While carbon containing molecules just adsorb on the surface and do not form carbide. In the bulk of the deposited layer almost pure TiN was found with some traces of oxygen and carbon. The part of carbon was bonded to TiC, which can be caused by ion sputtering during the depth profiling.