Materials Literature
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Densely pegylated particles that can serve as a model system for artificial cells were prepared by covalently grafting amino polyethylene glycol (PEG, molecular weight 3400 or 5000) onto carboxyl polystyrene particles (PS-COOH) using carbodiimide chemistry. PEG-modified particles (PS-PEG) were characterized by determi…
The effects of the adsorption of a simple dicarboxylate low molecular weight organic anion, maleate, on the dissolution of a model aluminum oxide, corundum (alpha-Al2O3), have been examined over a range of different maleate concentrations (0.125-5.0 mM) and pH conditions (2-10). In situ attenuated total reflectance Fo…
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Aromatic nanochannels were assembled about linear π-conjugated molecules. The novel supramolecular architectures are cemented by weak interactions and form crystals that melt at much higher temperatures than the standard molecular arrangement. The perfect fitting of the chains in the unusual environment is shown by th…
An alternative approach to nanostructured carbon materials relies on the use of covalently stabilized micellar precursors that are soluble in aqueous systems (see picture). These precursors belong to a class of shell cross-linked nanoparticles (SCKs) that are formed by self-assembly and stabilization of amphiphilic bl…
Following the discovery that small gold clusters highly dispersed on metal oxide supports are active catalysts at low temperature for a variety of reactions, a number of studies have been carried out to determine the structure of the clusters and the mechanism leading to their activity. A major deterrent to the use of…
Getting the blues: Electrochemical ring-closing is observed for the photochromic bis(pyridinium) dication of the dithienylethene backbone in which the pale yellow ring-open isomer can be converted to its blue ring-closed isomer by either irradiation with UV light or by electrochemical reduction (see picture). The elec…
Solid-state NMR analysis on wurtzite 2-nm hexadecylamine-capped CdSe nanocrystals (CdSe-HDA) provides evidence of discrete nanoparticle reconstruction within the Se sublattice of the nanomaterial. The cadmium and selenium atoms are probed with (1)H-(113)Cd and (1)H-(77)Se cross-polarization magic angle spinning (MAS)…
In summary, we have presented a suitable approach to obtain surfactant-stabilized suspensions of long, individually dispersed SWCNTs essentially free of bundles. The combination of mild tip and bath ultrasonication has proven effective in unbundling the SWCNT ropes and, at the same time, in minimizing tube shortening.…
The α-Keggin ions [TNb12O40]16− (T=Si, Ge) have been synthesized hydrothermally as water-soluble sodium salts. These clusters are very highly charged, and are bound to their charge-balancing sodium atoms in the solid state (see picture). NMR spectroscopy experiments show that the sodium atoms remain strongly associate…
The synthesis of well-defined luminescent organoboron polymers via a novel three-step procedure starting from silylated polystyrene is reported. Highly selective borylation of poly(4-trimethylsilylstyrene) (PS-Si), followed by replacement of the bromine substituents in poly(4-dibromoborylstyrene) (PS-BBr) with substit…
We have first succeefully synthesized the sodium cobalt oxyhydrate superconductors using KMnO4 as a de-intercalating and oxidizing agent. It is a novel route to form the superconductive phase of NaxCoO2.yH2O without resorting to the commonly used Br2/CH3CN solution. The role of the KMnO4 is to de-intercalate the Na+ f…
In strong-coupling superconductors with a short electron mean free path the self-energy effects in the superconducting order parameter play a major role in the phonon manifestation of the point-contact spectra at above-gap energies. We compare the expressions for the nonlinear conductivity of tunnel, ballistic, and di…
An expression is derived for the strain energy of a polymer chain under an arbitrary three-dimensional deformation with finite strains. For a Gaussian chain, this expression is reduced to the conventional Moony--Rivlin constitutive law, while for non-Gaussian chains it implies novel constitutive relations. Based on th…
Single receptor-ligand bonds have finite lifetimes, so that biological systems can dynamically react to changes in their environment. In cell adhesion, adhesion bonds usually act cooperatively in adhesion clusters. Outside the cellular context, adhesion clusters can be probed quantitatively by attaching receptors and…
Slow relaxation of the magnetization reveals the single-molecule magnetic behavior of [Mn2(saltmen)2(ReO4)2] (saltmen2−=N,N′-(1,1,2,2-tetramethylethylene)bis(salicylideneiminate), a simple, out-of-plane MnIII dimeric complex containing a [MnIII(μ-O)2MnIII] core (see structure shown, Mn brown, O red, N blue, Re pink).…
The optical absorption spectrum of the carbon (4,2) nanotube is computed using an ab initio many-body approach which takes into account excitonic effects. We develop a new method involving a local basis set which is symmetric with respect to the screw-symmetry of the tube. Such a method has the advantages of scaling f…
A new synthetic route to poly-3,4-ethylenedioxythiophene (PEDT) with a conductivity exceeding 1000 S/cm is described. The method is based on base-inhibited vapor-phase polymerization, where a surface covered with ferric p -toluenesulfonate as oxidant mixed with a volatile base (pyridine) is exposed to 3,4-ethylenediox…
The computer program JECP/SP, written in Java, for generating stereographic projections, possesses additional functionality applicable to specimen orientation adjustment using the specimen holder in transmission electron microscopy (TEM). The extension can be used to minimize the difficulties encountered when tilting…
The traditional way of measuring intensities in surface X-ray diffraction experiments is by performing rocking scans. Owing to experimental time limitations, this rather slow procedure leads to incomplete data sets for large surface unit cells. This lack of information not only may affect adversely the accuracy of the…