Materials Literature
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Durch den Einbau von miteinander wechselwirkenden Laserfarbstoffen an den Kettenenden und im Brennpunkt eines dendritischen Makromoleküls kann Energie unterschiedlicher Wellenlängen, die durch die große periphere Antenne des Dendrimers gesammelt wurde (siehe linkes Bild), direkt und mit hohem Wirkungsgrad auf den zent…
Band structure calculations from first principles provide the basis of a simple explanation for the appearance of ferromagnetism in iron, cobalt, and nickel that is founded upon a uniquely chemical concept: bonding. It is shown that the onset of ferromagnetism strengthens the metal-metal bonds in these transition meta…
The crystalline, spinless π dimer (1.+⋅PF6)2 was obtained by the oxidation of bipyrrole 1 with ferrocenium hexafluorophosphate. The diamagnetic species generated electrochemically in solution was identified as the σ dimer by NMR spectroscopy.
Sintering, structural correlations and mechanical behavior of nanophase silica glasses are investigated using large-scale, parallel molecular-dynamics simulations. During the sintering process, the pore sizes and distribution change without any discernible change in the pore morphology. The height and position of the…
The influence of post-sintering annealing on the dielectric relaxation behavior was studied in (Sr1−1.5xLax)TiO3 in the temperature range of 1.5–300 K. The results show that the dielectric permittivity peaks with frequency dispersion can be gradually and absolutely eliminated by annealing in an oxidizing atmosphere, a…
Length-dependent charge redistribution in dangling-bond (DB) linear chains fabricated on a hydrogen-terminated $\mathrm{Si}(100)\ensuremath{-}(2\ifmmode\times\else\texttimes\fi{}1)$ surface is analyzed by using scanning tunneling microscopy and first-principles calculations. The second-layer Si atoms are displaced alt…
Die lösungsmittel- und katalysatorfreie Kondensation von Pyrrol und Aldehyden bietet einen äußerst einfachen Zugang zu neuartigen Corrolen [Gl. (1); Ar = C6F5, 2,6-F2C6H3, 2,6-Cl2C6H3]. Das Pentafluorphenyl-substituierte Produkt (Ar = C6F5) ist eine exzellente Vorstufe für andere Derivate, einschließlich eines ionisch…
A three-dimensional network with one-dimensional channels (see picture) has been self-assembled from the nickel(II) complex of cyclam and 1,3,5-benzenetricarboxylate in water through hydrogen-bond formation. The channels have an appropriate diameter (10.3 Å) to include D-glucose with a formation constant of Kf=(1.38±0…
Addition of Nd, Tb, or Dy to amorphous Ti–O thin films is found to improve the dielectric properties of the films. Specifically, substitution of 10–30 at. % of the dopant for Ti is found to dramatically decrease the leakage current, increase the breakdown voltage, and yet retain the relatively high dielectric constant…
It is completely plausible that unmodified materials of natural origin, such as the native macromolecules cellulose or starch, are biodegradable. If these materials are modified then degradation may, depending on the degree of modification, be more difficult or even impossible. In the same manner synthesized macromole…
The thermal stability and relaxation processes in hydrogen free diamond-like-carbon films with different sp3 fractions (40%, 60%, and 80%) are comparatively studied for the first time by visible Raman spectroscopy. The 80% sp3 film is very stable under annealing in the entire temperature region investigated (300–1270…
The formation of boron nitride (BN) nanotubes via a solid-state process is demonstrated. The nanotubes are produced by first ball-milling hexagonal BN powder to generate highly disordered or amorphous nanostructures, followed by annealing at temperatures up to 1300 °C. The annealing leads to the nucleation and growth…
Porous alumina membranes with ordered pore arrays were prepared electrochemically from Al metal in C2H2O4 or H2SO4. Photoluminescence (PL) measurements show that a blue PL band occurs in the wavelength range of 400–600 nm. This band originates from singly ionized oxygen vacancies (F+ centers) in porous alumina membran…
Hydrogen bonds between urea units allow self-organization of π systems in mono- and bithiophenes into fibers as shown schematically. In these fibers there is a surprisingly high mobility of charge carriers as determined by pulse-radiolysis time-resolved microwave conductivity measurements.
Electromigration in 0.15–10 μm wide and 0.3 μm thick Cu lines deposited by physical vapor deposition has been investigated using both resistance and edge displacement techniques in the sample temperature range 255–405 °C. For wide polycrystalline lines (>1 μm), the dominant diffusion mechanism is a mixture of g…
By the attachment of interacting laser dyes to the chain ends and focal point of a dendritic macromolecule it is possible to funnel energy harvested by the large peripheral antenna of the dendrimer (see picture on the left) efficiently and directly to the central fluorescent core (picture in the middle) by a process t…
To understand the near-interface magnetism in manganites, ultrathin films of La0.67Sr0.33MnO3 were grown epitaxially on single-crystal (001) LaAlO3 and (110) NdGaO3 substrates. The temperature and magnetic field-dependent film resistance is used to probe the film’s structural and magnetic properties. A surface and/or…
Thin films of quantum size ZnO particles were fabricated by electrophoretic deposition from stable colloidal suspensions. The average particle size and hence the optical properties can be tailored by controlling the aging time and temperature of the suspensions. Thin films prepared by electrophoretic deposition exhibi…
The solvent-free, catalyst-free condensation of pyrrole and aldehydes provides an extremely facile synthetic pathway to novel corroles [Eq. (1); Ar=C6F5, 2,6-F2C6H3, 2,6-Cl2C6H3]. The product containing pentafluorophenyl groups is an excellent precursor of other derivatives, including an ionic, water-soluble corrole.
Although progress has been made in the ab initio simulation of lattice dynamics in semiconducting crystals, information about the relaxation of nonequilibrium lattice vibrations remains incomplete. This work studies the relaxation times of room-temperature thermal phonons through measurements of thermal conduction alo…