Materials Literature
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Three molecular components self-assemble through zinc–pyridine coordination interactions to form a stable porphyrin pentamer (see picture). In this supramolecular complex energy absorbed by the outer zinc porphyrins is transferred to a central free-base porphyrin in 500 picoseconds.
We report the deposition of a-Si:H on thin films of free-standing single crystalline ZnO columns. The ZnO columns have a height of several μm and a diameter between 100 and 200 nm. The ZnO films are prepared in electrodeposition and have considerable potential for use in photoelectric thin film devices. Morphology, el…
Carbon nanotubes aligned perpendicular to a surface are used as electrodes to form novel, conducting polymer–carbon nanotube (CP–NT) composites. The SEM image (see picture) shows the CP–NT coaxial nanowires, in which an appropriate conducting polymer film is electrochemically deposited onto the carbon nanotube arrays…
We propose a new and general method for discovering novel ordered phases of block copolymer melts. The method involves minimizing a free energy functional in an arbitrary unit cell with respect to the composition profile and the dimensions of the unit cell, without any prior assumption of the microphase symmetry. Vary…
Senkrecht auf einer Oberfläche angebrachte Kohlenstoff-Nanoröhren werden als Elektroden für die Bildung leitfähiger Polymer-Kohlenstoff-Nanoröhren (Nanodrähte) verwendet. Die SEM-Aufnahme (siehe Bild) zeigt die Entstehung der Nanodrähte durch Abscheiden des leitfähigen Polymerfilms auf den teilweise in die Elektrolytl…
Carbon nanotubes with junctions are considered to be of potential value in nanoelectronics. A simple pyrolysis procedure for producing Y-junction carbon nanotubes is described. The method involves the pyrolysis of the organometallic precursor, nickelocene, along with thiophene at 1273 K. Tunneling conductance measurem…
High pressure structural distortions of the hexagonal close packed (hcp) element zinc have been a subject of controversy. Earlier experimental results and theory showed a large anomaly in lattice strain with compression in zinc at about 10 GPa which was explained theoretically by a change in Fermi surface topology. La…
Structure factors for $\mathrm{Ca}{}_{x/2}\mathrm{Al}{}_{x}\mathrm{Si}{}_{1\ensuremath{-}x}\mathrm{O}{}_{2}$ glasses $(x\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0,0.25,0.5,0.67)$ extended to a wave vector of magnitude $Q\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}40\phantom{\rule{0ex}{0ex}}\AA{}{}^{\e…
Half-Heusler alloys (MgAgAs type) with the general formula MNiSn where M is a group IV transition metal (Hf, Zr, or Ti) are currently under investigation for potential thermoelectric materials. These materials exhibit a high negative thermopower (−40 to −250 μV/K) and low electrical resistivity values (0.1–8 mΩ cm) bo…
Electronic transport measurements were performed on Y-junction carbon nanotubes. These novel junctions contain a large diameter tube branched into smaller ones. Independent measurements using good quality contacts on both individual Y junctions and many in parallel show intrinsic nonlinear transport and reproducible r…
Dendrimeric catalysts can present catalytic units in close proximity, thereby inducing useful cooperative effects (see picture). Commercial dendrimers were derivatized with chiral [Co(salen)] complexes and found to display enhanced reactivity relative to monomeric or even dimeric analogues in the hydrolytic kinetic re…
An extended network, {[Dy4(OH)4(asp)3(H2O)8](ClO4)2⋅10 H2O}n, having three-dimensional channels with a spacing of 11.78 Å (see picture) has been prepared by mixing Dy(ClO4)3 and L-aspartic acid in aqueous solution, and subsequently adjusting the pH values to about 6.5 using aqueous NaOH solution. This open-framework c…
Anomalous lattice expansions have been measured for the first time in monodisperse CeO2-x nanoparticles and in BaTiO3 single nanoparticles by electron diffraction. X-ray photoelectron spectroscopy studies on CeO2-x nanoparticles and ab initio computer simulation on BaTiO3 clusters show that the origin of expansion is…
Hydrogen-terminated diamond exhibits a high surface conductivity (SC) that is commonly attributed to the direct action of hydrogen-related acceptors. We give experimental evidence that hydrogen is only a necessary requirement for SC; exposure to air is also essential. We propose a mechanism in which a redox reaction i…
A simple and effective method is presented for producing light-emitting porous silicon (PSi). A thin (d<10 nm) layer of Au, Pt, or Au/Pd is deposited on the (100) Si surface prior to immersion in a solution of HF and H2O2. Depending on the type of metal deposited and Si doping type and doping level, PSi with di…
We have found that near the metal-insulator transition of Al 70 Pd 22.5 Re 7.5 quasicrystal, the conductivity σ( T ) obeys σ( T )=σ(0)+ m T 1/3 between 1.5 K and ∼10 K on both sides of the metal-insulator transition, as found in disorder systems. This indicates that the conductivity near the metal-insulator transition…
beta-Lactams inhibit a range of enzymes via acylation of nucleophilic serine residues. Certain gamma-lactam analogues of monocyclic beta-lactams have also been shown to be reversible inhibitors of porcine pancreatic elastase (PPE), forming acyl-enzyme complexes that are stable with respect to hydrolysis. Crystallograp…
Photoluminescence (PL) spectra of undoped and neutron-transmutation-doped InSe samples at 15 K are reported. The undoped InSe PL spectrum clearly shows the free exciton line and an exciton-neutral acceptor complex recombination. A structure of partially resolved transitions is observed between 1.315 and 1.330 eV, whos…
Caesium vanadium(V) selenite contains infinite sheets of distorted vertex-sharing VO6 octahedra, capped by selenite groups [dav(V—O) = 1.927 (4) Å and dav(Se—O) = 1.709 (3) Å]. Interlayer caesium cations complete the structure [dav(Cs—O) = 3.365 (4) Å].
The structure of strained Cu films deposited on Ru(0001) surfaces at 720 K was investigated by x-ray diffraction techniques. Our analysis shows that a single Cu monolayer adopts a pseudomorphic structure with the first three interlayer spacings significantly relaxed. The two-layer structure consists of a commensurate,…