Materials Literature
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Water-soluble poly(3-thiophene acetic acid) (P3TAA) and its copolymers with 3- n -methylthiophene or with 3- n -octadecylthiophene were synthesized. The solution properties of these water-soluble polythiophene carboxylic acids were studied by potentiometric titration, viscosity measurements, and UV−visible spectroscop…
The Burridge-Knopoff model of earthquake faults with viscous friction is equivalent to a van der Pol-FitzHugh-Nagumo model for excitable media with elastic coupling. The lubricated creep-slip friction law we use in the Burridge-Knopoff model describes the frictional sliding dynamics of a range of real materials. Low-d…
The synthesis, crystal structure, and magnetic characterization of a novel tetranuclear iron(III) methoxo-bridged cluster of formula Fe 4 (OCH 3 ) 6 (dpm) 6 (where Hdpm = dipivaloylmethane) is reported. The cluster has a ground spin state of S = 5, which is selectively populated below 20 K. High-field EPR spectra reve…
A new method has been demonstrated to synthesize highly oriented mesostructured coatings of tungsten oxide/surfactant composites on amorphous substrates by a shear-flow-induced deposition mechanism. The applied flow field provides convective transport of film precursors and orients the domains of the mesostructure, re…
Near-infrared (NIR) Fourier transform (FT) surface-enhanced Raman scattering (SERS) spectra were measured for Langmuir−Blodgett (LB) and dipping films of azobenzene-containing long-chain fatty acids ( n A m H, n = 8, 12, m = 3, 5) on silver substrates prepared by silver mirror and nitric acid etched silver foil method…
We report on the efficient photooxidation of hexapropyl bis(dimethylamino) zinc porphyrazine. The process is shown to be autocatalytic. The triplet state of the seco -ZnPz sensitizes the formation of excited-state singlet oxygen with a quantum yield of 0.54 and subsequent cleavage of the pyrrole double bond occurs to…
The re-oxidation of slightly reduced TiO 2 (110) surfaces by exposure to an oxygen pressure of ~2 × 10 -7 mbar in the temperature range 473-1000 K occurs by re-growth of TiO 2 overlayers by diffusion of Ti n + interstitials from the bulk. Starting with a (1 × 2) reconstructed surface, scanning tunnelling microscope im…
In this work we have investigated how the dynamics of poly(vinyl methyl ether), PVME, changes by blending with deuterated polystyrene. The experimental techniques used were dielectric spectroscopy, quasielastic neutron scattering, and 13 C nuclear magnetic resonance. By means of these techniques, the dynamics of the p…
The preparation and characterization of a series of encapsulated-lanthanide 15-metallacrown-5 complexes are reported. Planar ligands such as picoline hydroxamic acid (picha) or nonplanar alpha-amino hydroxamic acids (e.g., glycine hydroxamic acid (glyha)) led to one-step syntheses of metallacrowns in yields as high as…
The stability of a quasicrystalline structure, recently obtained in a molecular-dynamics simulation of rapid cooling of a binary melt, is analyzed for binary hard-sphere mixtures within a density-functional approach. It is found that this quasicrystal is metastable relative to crystalline and fluid phases for diameter…
An advanced potentiometric pH transducer based on processible polyaniline (PCPAn) is reported on. Both glassy carbon and screen-printed carbon electrodes modified with PCPAn by dip-coating exhibited a fully reversible potentiometric response of approximately 90 mV/pH unit over the range from pH 3 to 9. Such a signific…
The effective elasticity of highly charged stiff polyelectrolytes is studied in the presence of counterions, with and without added salt. The rigid polymer conformations may become unstable due to an effective attraction induced by counterion density fluctuations. Instabilities at the longest, or intermediate length s…
The magnetophotoluminescence (MPL) behavior of a GaAs/Al(0.3)Ga(0.7)As single heterojunction has been investigated to 60T. We observed negatively charged singlet and triplet exciton states that are formed at high magnetic fields beyond the nu=1 quantum Hall state. The variation of the charged exciton binding energies…
Coulomb driven, magneto-optically induced electron and hole bound states from a series of heavily doped GaAs/Al(0.3)Ga(0.7)As single heterojunctions (SHJ) are revealed in high magnetic fields. At low magnetic fields (nu > 2), the photoluminescence spectra display Shubnikov de-Haas type oscillations associated with the…
Over 100 oligoporphyrin (porphyrin molecules fused to each other through rigid acene-type bridges) molecules have now been synthesized, their long rigid π-bonded structures making them very suitable as molecular wires while their synthetic flexibility offers the possibility of tailoring their structural and electronic…
The amount of hydrogen adsorbed in arrays of single-walled carbon nanotubes has been studied as a function of the geometry of the array. The tube lattice spacing has been varied to optimize hydrogen uptake. Two different lattice geometries have been examined, namely, the triangular lattice and the square lattice. None…
A sudden drop in mechanical friction, between an adsorbed nitrogen monolayer and a lead substrate, occurs when the lead passes through the superconducting transition temperature. We attribute this effect to a sudden drop at the superconducting transition temperature of the substrate Ohmic heating. The Ohmic heating is…
Using a generalization of the Poisson-Boltzmann equation, dynamics of counterion condensation is studied. For a single charged plate in the presence of counterions, it is shown that the approach to equilibrium is diffusive. In the far from equilibrium case of a moving charged plate, a dynamical counterion condensation…
By means of molecular dynamics computer simulations we investigate the out of equilibrium relaxation dynamics of a simple glass former, a binary Lennard-Jones system, after a quench to low temperatures. We study both one time quantities and two-times correlation functions. Two-times correlation functions show a strong…
The experimentally predicted narrowing in the bandwidth of sodium is interpreted in terms of the non-local self-energy effect on quasi-particle energies of the electron liquid. The calculated self-energy correction is a monotonically increasing function of the wavenumber variable. The usual analysis of photo-emission…