Materials Literature
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We describe a method to reliably pattern monolayers of iron nanoparticle (FeNP) colloids into submicron features for growth of single-walled carbon nanotubes (SWNTs) by chemical vapor deposition. Our process results in very clean patterns that are readily imaged by atomic force microscopy, which has allowed the observ…
MOTIVATION: The lack of standards for storage and exchange of data is a serious hindrance for the large-scale data deposition, data mining and program interoperability that is becoming increasingly important in bioinformatics. The problem lies not only in defining and maintaining the standards, but also in convincing…
Take a length of ribbon: Mesoporous silica ribbons that are typically 50–250 nm thick, 0.4–1.5 μm wide, and hundreds of micrometers long were prepared by a one-phase approach with cationic surfactants as templates under acidic conditions, and their cross-sections were studied by SEM and TEM techniques (see picture).
Synthesis, chain characteristics, and time-dependent viscoelastic response of polyhedral oligomeric silsesquioxanes (POSS)-containing hybrid polymers were investigated. Unlike many other reported POSS hybrid copolymers works, the POSS-grafted copolymers used in this study, although having different amounts of POSS att…
Switching signs: The polar structure of a tilted smectic C phase formed by a homologous series of bent-core mesogens changes from antiferroelectric to ferroelectric with increasing chain length. The polar switching of the banana-shaped molecules occurs by collective rotation around their long molecular axes (a) or by…
The effects of the OH group on the electronic and optical properties of single-wall carbon nanotubes were investigated using first principles electronic structure calculations. Our results confirm band-gap reduction of semiconductor carbon nanotubes up on addition of the OH group. An additional energy level emerges ne…
Using molecular-dynamics simulation, we calculate the distribution of atomic jumps in ${\mathrm{Cu}}_{33}{\mathrm{Zr}}_{67}$ in the liquid and glassy states. In both states the distribution of jump lengths can be described by a temperature-independent exponential of the length and an effective activation energy plus a…
Green fields of nanowires: Germanium, a Group IV semiconductor, can act as an efficient catalyst for high-rate (up to 400 μm h−1) growth of very long (up to 200 μm), extremely straight, and quasi-aligned arrays of single-crystalline ZnO nanowires (see picture). The diameter of the Ge particles (0.5–4 μm) is about 5–15…
A general method for entrapment of hydrophobically coated nanocrystals in micrometer and submicrometer composite silica spheres, nano@micro, was developed. The method employs two starting solutions hydrophobic solvent containing the sol−gel precursor, a polymer, and the nanocrystals, and an emulsifying hydrophilic pha…
Softly, softly: VS2 nanotubes (see electron micrograph, layer separation 1.6 nm) are prepared from vanadium oxide nanotubes by a “chimie douce” process. The VS2 nanotubes are remarkably stable; the corresponding bulk compound is unstable unless it is intercalated with alkali-metal atoms. The nanotubes reversibly inter…
Bioinspiration: Polar assembly (a feature of many natural protein-based fibrous structures, such as actin, microtubules, intermediate filaments, and collagens) is demonstrated in a straightforward, synthetic, peptide-based fiber system of de novo design (see false-color confocal-microscope image of fibers). This findi…
The high-nuclearity bismuth oxo cluster [Bi22O26(OSiMe2tBu)14] (see structure) was obtained by partial hydrolysis of Bi(OSiMe2tBu)3. A hydrophobic layer of silanolate groups covers the bismuth oxo core, the structure of which is closely related to that of β-Bi2O3. Both the bismuth oxo cluster and the bismuth silanolat…
Any old ion? Two bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) radical salts with ion channels of stacked [18]crown-6 and Cat/H2O molecules (Cat=H3O+ or NH4+) are described. The structures contain alternating BEDT-TTF layers, [(Cat)M(C2O4)3]2− (M=Ga, Cr) layers, and the [18]crown-6 ion channels (see picture). The s…
We describe the synthesis of two cyclobutadiene(cyclopentadienyl)cobalt-containing poly(p-phenylene ethynylene)s (PPEs) and their use as precursors for stable ceramic surface coatings. Organometallic PPEs were shaped into hexagonally ordered assemblies by using the breath-figure method. Such breath figures can be wash…
We examine the static and dynamic properties of polymer chains in a melt in the presence of a solid surface. A molecular dynamics simulation is carried out using a coarse-grained bead−spring model of polymer chains. Both attractive and repulsive interactions between surface and monomers are examined. Static conformati…
Shape sorting: The incorporation of a flexible coil of variable length into a rigid wedge-shaped building block leads to the spontaneous formation of a rich variety of supramolecular structures. These include a bilayer lamellar structure with in-plane hexagonally ordered perforations (see picture, R=(CH2)13CH3).
The unusual magnetic behavior of [Ru2(μ-O2CMe)(μ-DPhF)3(H2O)]BF4⋅0.5 CH2Cl2 (1; DPhF=N,N′-diphenylformamidinate), which is intermediate between that of compounds with spin states S=1/2 and S=3/2, is attributed to a quantum mechanical spin admixture. This phenomenon results from a multiple bond between the metal atoms…
A series of red and blue highly fluorescent core-substituted naphthalene bisimide dyes has been synthesized and they have been investigated as supramolecular building blocks. NMR and UV-Vis titration experiments of these dyes with complementary melamines revealed the formation of triple hydrogen bonds (DAD-ADA arrays)…
Only C and N atoms are present in the high-nitrogen compound 4,4′,6,6′-tetra(azido)azo-1,3,5-triazine (TAAT), which is thus an ideal precursor for carbon nitrides. Controlled pyrolysis of TAAT afforded novel nitrogen-rich carbon nitrides in the form of nanolayers (C2N3), nanoclusters (C3N5), and nanodendrites (C3N5, s…
Conformation-dependent tuning of color: Starting from aryloxy-substituted perylene bisimides two isomeric diagonally (A) and laterally (B) bridged macrocycles were synthesized (see picture) for three different bridge lengths. These isomers comprise different conformational features and can, therefore, be used as molec…