Materials Literature
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Effizienter Gastaustausch: In einer Iodatmosphäre zeigt das organische Zeolithanalogon TPP⋅x(THF) (x=0.35–0.6) eine sofortige I2-Sorption. Der zuvor farblose Kristall (a) färbt sich an den Kristallenden (b) und ist nach 1–2 Tagen vollständig mit I2 durchdrungen (c). Die elektrische Leitfähigkeit der TPP⋅y(I2)-Kristall…
Sechs Mo-Dimere, die um ein zentrales PO4-Tetraeder gruppiert sind, bilden den Kern des neuartigen, von vier {La(H2O)4}3+-Einheiten umgebenen ε-Keggin-Polyoxokations [ε-PMo12O36(OH)4{La(H2O)4}4]5+ (siehe Struktur). 31P-NMR-spektroskopische Untersuchungen ergaben, dass ε-Keggin-Ionen in wässriger Lösung nicht stabil si…
Abstract A stress‐induced crystallization model for semicrystalline plastics is proposed based on the theory that stress‐induced orientation of molecules and chains increase the melting temperature of thermoplastics, and hence, the supercooling which is the driving force for crystallization. By assuming that the effec…
A detailed investigation of local structure and phase transitions in copper iodide (CuI), at high temperatures, has been carried out performing x-ray absorption spectroscopy (XAS), x-ray absorption temperature scans, and energy scanning x-ray diffraction measurements. Low-noise XAS spectra have been recorded in a wide…
This report describes a straightforward, metathesis (exchange) reaction between gallium chloride and sodium azide that produces gallium nitride nanoparticles below 210 °C. Slowly heating these two reagents together circumvents rapid, exothermic reactions, which can decompose the nitride product. The resulting GaN powd…
The kinetics of oxygen-atom transfer from the peroxo complexes of methyltrioxorhenium (MTO) to alkenes in ionic liquids have been investigated. Noncatalytic conversions of alkenes to epoxide were monitored by UV/Vis at 360 nm, where the monoperoxorhenium (mpRe) and diperoxorhenium (dpRe) complexes absorb. Water- and p…
New wheels: The 1:2 reaction of ferric nitrate with benzilic acid (Ph2C(OH)COOH) in methanol at pH≈4.0 results in the formation of a new member of the molecular ferric-wheels family with the carboxylatobis(alkoxo) bridging unit. The molecular structure of [{Fe(OMe)2[Ph2C(OH)COO]}12] (see picture) consists of a centros…
Zapfenförmige Fluorophore an den Ausgängen von Zeolith-L-Kanälen können elektronische Anregungsenergie von Pyronin+-Molekülen im Innern des Kristalls abfangen (siehe Schema, oben). Den umgekehrten Vorgang, d. h. das Einspeisen elektronischer Anregungsenergie durch solche „Zapfen“ (unten), erreicht man mit Oxonin+-Mole…
Starting from five different Si−B−C−N polymeric precursors with B/N atomic ratios ranging from 1:3 to 1:0.5, ceramic materials were synthesized by thermolysis at 1400 °C in about 70−75% yield. During this transformation, the Si/B/N ratio remained roughly constant, whereas H and C contents were reduced. The crystalliza…
The amyloid fibril is a misfolded and undesirable state for proteins that has been proposed to be a causative agent for a variety of fatal diseases known as amyloid diseases, such as Alzheimer's and prion diseases. However, the fibril has a highly ordered tertiary structure in which numerous beta-strand polypeptide ch…
An oxa-analogue of 5,10,15-triarylcorrole, i.e., 5,10,15-triaryl-21,23-dioxacorrole (21,23-O(2)Cor)H, where two pyrrole rings are replaced by furan moieties, has been produced by condensation of 2,5-bis(arylhydroxymethyl)furan, 2-phenylhydroxymethylfuran, and pyrrole. 2-Phenylhydroxymethylfuran serves as the suitable…
Ligand formed by CN bond cleavage: Transition-metal-promoted heterolytic cleavage of the CN bond in 1 results in the formation of five new complexes of cis hyponitrite with Group 10 transition metals. The new complexes include [Ni(η2-O2N2)(dppf)] (dppf=1,1′-bis(diphenylphosphanyl)ferrocene) which is structurally cha…
A set of twelve porphyrin dimers has been prepared to give information on how the type of connectivity between a porphyrin core and a bridge can influence the interporphyrin electronic interaction. The new porphyrin systems are substituted directly at the meso position with an oligothiophene chain tethered either with…
We examine the Mn concentration dependence of the electronic and magnetic properties of optimally annealed ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}$ epilayers for $1.35%<~x<~8.3%.$ The Curie temperature ${(T}_{c}),$ conductivity, and exchange energy increase with Mn concentration up to $x\en…
Abstract The modification of high‐impact polystyrene (HIPS) was accomplished by melt‐grafting glycidyl methacrylate (GMA) on its molecular chains. Fourier transform infrared spectroscopy and electron spectroscopy for chemical analysis were used to characterize the formation of HIPS‐g‐GMA copolymers. The content of GMA…
Abstract Jute fibers were treated with 5% NaOH solution for 4 and 8 h, respectively, to study the mechanical and impact fatigue properties of jute‐reinforced vinylester resin matrix composites. Mechanical properties were enhanced in case of fiber composites treated for 4 h, where improved interfacial bonding (as evide…
Nicht chiral und doch ferroelektrisch: Bei konventionellen fluiden Systemen heben sich die Dipolmomente der einzelnen Moleküle gegenseitig auf, und eine makroskopisch apolare Struktur entsteht. Hier wird gezeigt, wie sich durch gezieltes Moleküldesign und Nutzung von Mikrosegregationseffekten die Selbstorganisation vo…
Der chirale Organokatalysator Bisflavin 1 katalysiert asymmetrische Baeyer-Villiger-Reaktionen von Cyclobutanonen mit H2O2 (siehe Schema). Die entsprechenden Lactone werden mit bis zu 74 % ee erhalten.
Photoluminescence (PL) from composites of 7- and 15-nm silica (amorphous ${\mathrm{SiO}}_{2})$ nanoparticles and bulk type-III fused silica induced by two-photon band-to-band excitation with 193-nm (6.4-eV) ArF laser light has been measured in time-resolved detection mode. The PL spectra taken for 15-nm particles allo…
Stopcock fluorophores at the ends of zeolite L channels can trap electronic excitation energy from pyronine+ molecules inside the crystal (see scheme, top). The reverse process, that is, the injection of electronic excitation energy through such stopcocks (bottom), was achieved with oxonine+ molecules inside the zeoli…