Materials Literature
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The influence of deposited Pt metal clusters on the CO photooxidation reaction on the TiO 2 (110) surface was investigated. An enhancement in the CO photooxidation reaction rate or yield is not observed in the presence of Pt metal clusters on the TiO 2 (110) surface. These results indicate that kinetic models involvin…
Tissue engineered lamb heart valve leaflets (N - 3) were constructed by repeatedly seeding a concentrated suspension of autologous myofibroblasts onto a biodegradable synthetic polymeric scaffold composed of fibers made from polyglycolic acid and polylactic acid. Over a 2-week period the cells attached to the polymer…
The rate constants and activation parameters for water exchange on hexaaqua and monohydroxy pentaaqua iridium(III) have been determined by 17 O NMR spectroscopy as a function of temperature (358−406 K) and pressure (0.1−210 MPa) at several acidities (0.5−5.0 m ). Noncoordinating trifluoromethanesulfonate (CF 3 SO 3 -…
In applying the semiempirical intermediate neglect of differential overlap (INDO) method based on the Hartree-Fock formalism to a cubic perovskite-based ferroelectric material KNbO3, it was demonstrated that the accuracy of the method is sufficient for adequately describing the small energy differences related to the…
An implementation of the multiple-scattering approach to x-ray magnetic circular dichroism (XMCD) in K-edge x-ray absorption spectroscopy is presented. The convergence problems due to the cluster size and the relativistic corrections are solved using an expansion of the Dirac Green function for complex energies up to…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTRapid Synthesis of Dendrimers by an Orthogonal Coupling StrategyFanwen Zeng and Steven C. ZimmermanView Author Information Department of Chemistry, University of Illinois Urbana, Illinois 61801 Cite this: J. Am. Chem. Soc. 1996, 118, 22, 5326–5327Publication Date (Web)…
The present study (see ref 1) delineates the scope and limitations of porphyrin chromophores for structural studies by the exciton coupled circular dichroic (CD) method. A distance dependency of the porphyrin coupling was investigated in the range between 10 and 50 Å. Over short interchromophoric distances, significan…
Charge-transfer (CT) exciton effects are investigated for the optical absorption spectra of crosslinked C60 systems by using the intermediate exciton theory. We consider the C60-dimers, and the two (and three) molecule systems of the C60-polymers. We use a tight-binding model with long-range Coulomb interactions among…
We determine dephasing times T2 in free standing porous silicon samples using nondegenerate four-wave mixing. Within the framework of an idealized inhomogeneously broadened two-level system, values of 20 fs for different porosities are obtained. Fast energy relaxation times are found in the range of 1.5–3.5 ps for 64%…
Surprisingly stable is the dinuclear complex cation [1CuCu]2+ with entwined ligand 1 (shown on the right; •, ○ = Cu+) that can be demetalated in a stepwise manner. The singly demetalated complex [1Cu]+ can be converted to give dissymmetrical heterodi-nuclear complexes [1CuAg]2+ and [1CuZn]3+ (○ = Ag+ and Zn2+, respect…
Completely new materials arise when semiconductor nanoparticles are periodically ordered in superlattices. First pioneering preparations of such superlattices were achieved by self-organization of ligand-stabilized CdSe and CdS nanoparticles. The block polymerization to give micelles in the presence of gold salts and…
We have fabricated erbium–oxygen-doped silicon light emitting diodes with molecular beam epitaxy by simultaneously evaporating erbium and silicon and providing a suitable background pressure of oxygen. In reverse bias, the diodes show intense room-temperature electroluminescence at λ=1.54 μm, originating from the intr…
Four bands, all belonging to the main thallium centres, have been detected in the emission spectra of CsCl:Tl and CsBr:Tl crystals. Their spectral, polarization and kinetic characteristics have been studied from 0.45 up to 360 K. It has been shown that the new model proposed by us recently for the relaxed excited stat…
The EPR spectra of in two transition metal fluoride glasses (PZG and PBI) have been extensively studied as functions of temperature, concentration and microwave frequency (S, X, K and Q bands). The marked changes observed in the EPR spectra with temperature and concentration imply the existence of pairs of ions. The s…
We present a stable simple cubic structure in the quaternary system (Al - Si) - Cu - Fe with the composition which corresponds to the p/q = 1/1 cubic approximant of the icosahedral Al - Cu - Fe phase. This cubic structure, with lattice parameter a = 12.330 Å and density , contains roughly 135 atoms per unit cell. Prel…
A strong reducing power in the excited state is just one of the features of the tetranuclear copper(I) complex 1. It contains an acetylide dianion bridging four copper atoms in both η1 and η2 bonding modes and exhibits long-lived luminescence. The central framework of the structure is shown on the right.
The kinetics of phase separation in thin polymer blend films of polystyrene and polybutadiene on a silicon substrate is examined by optical microscopy of the free film boundary. Our observations on 1000 and 200 \AA{} films are consistent with a crossover from three- to two-dimensional spinodal decomposition kinetics i…
As deduced from Nature, the principle of symmetry-driven self-assembly, based on incommensurate coordination numbers, is employed to design clusters using metal coordination as the driving force. The ten-component cluster on the right demonstrates the predicted cooperativity in cluster formation.
The kinetics of solid-solid phase transitions are explored using pressure-induced structural transformations in Si nanocrystals. In agreement with the predictions of homogeneous deformation theories, large elevations in phase transition pressure are observed in nanocrystals as compared to bulk Si, and high pressure x-…
Abstract Zwar steht der Entwicklung von nanometergroßen Strukturen prinzipiell nichts im Wege, doch setzt sich immer mehr die Auffassung durch, daß sich Strukturminiaturisierungen unter die gegenwärtig durch lithographische Techniken erreichbare 1‐μ‐Grenze als nicht mehr praktikabel erweisen werden. Es wurde daher deu…