Materials Literature
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Thin films of poly[styrene- block -(2-vinylpyridine)] with equally long blocks were prepared by casting micellar toluene solutions on a mica or carbon substrate. The structure of the films was studied by scanning force microscopy and transmission electron microscopy. Structural variations were observed depending on th…
The utility of employing a variable duty cycle pulsed plasma polymerization technique to control film chemistry during plasma depositions is examined using allyl alcohol as monomer gas. Large scale progressive variations in film composition are observed with sequential changes in the plasma duty cycles employed, all o…
The often observed decrease in relative permittivity (ε‘) and refractive index ( n ) that accompanies fluorine substitution is the result of several effects. Fluorine replacement for hydrogen is known to decrease local electronic polarization and is thought to frequently increase fractional free volume. Both of these…
A new family of molecular squares containing ReI polypyridyl and polypyrazyl centers has been synthesized at quantitative yields via a self-assembly method. Ambient-temperature photophysical studies reveal that two of the squares (4,4‘-bipyridine- and pyrazine-bridged species) readily luminesce in solution from relati…
The effects of applied electric fields and solvent polarity on the linear and nonlinear optical (NLO) properties of three prototypical merocyanine (donor−conjugated pathway−acceptor) chromophores of differing architectural types are analyzed using semiempirical INDO/1 calculations in the presence of imposed static ele…
Phthalocyanines and related compounds can self-assemble into columnar structures in the solid and liquid crystalline state, in Langmuir–Blodgett films and in solution. This paper presents an overview of supramolecular architectures that have been constructed using several phthalocyanine and porphyrazine building block…
The backbone dihedral angle φ in polypeptides is characterized by four different J couplings: 3 J H N H α, 3 J H N C ‘, 3 J H N C β, and 3 J H α C ‘ . E.COSY and quantitative J correlation techniques have been used to measure these couplings in the protein human ubiquitin, uniformly enriched in 13 C and 15 N. Assuming…
We have demonstrated the synthesis of PbS nanoclusters within the microphase-separated films of diblock copolymers containing carboxylic acid units on one of the blocks. Lead was selectively sequestered into the acid containing domains by treating the polymer films with tetraethyllead, and PbS was formed by subsequent…
Aniline was polymerized in the presence of ultrafine colloidal silica particles (hydrodynamic diameter 35 nm) in aqueous media and, given a sufficient silica concentration, colloidally stable polyaniline−silica particles were obtained. The particle size of the resulting dispersions was determined by both dynamic light…
Adsorption of carbon monoxide on CuO/SiO2(1 wt.% CuO) and Cu-ZSM-5 (11 wt.% CuO) catalysts has been studied by IR spectroscopy. CO adsorption on CuO/SiO2 leads to formation of: (i) three kinds of unstable Cu2+—CO species detected only under equilibrium CO pressure and characterized by ν(CO) at 2216, 2199 and 2180 cm–1…
Addition of H 2 S and H 2 Se, in different proportions, to aqueous Cd(ClO 4 ) 2 solutions containing (NaPO 3 ) 6 led to the formation of coupled composite CdS−CdSe nanoparticles. Conversely, the sequential introduction of different amounts of H 2 S and H 2 Se (or H 2 Se and H 2 S) into aqueous Cd(ClO 4 ) 2 solutions c…
Analyses of biopolymer/calcium carbonate composites grown on inorganic abiotic substrates implanted between the shell and the shell-secreting epithelium of live red abalones ( Haliotis rufescens ) provide detailed spatial and temporal data on the in vivo assembly process that generates the shell. X-ray diffraction and…
Barium titanate (BaTiO 3 ) powders of varying particle sizes were grown under hydrothermal conditions at a temperature of 240 °C. This was accomplished by varying the hydroxide concentration of the reaction medium as well as the time required for synthesis. The spectroscopic, thermal, and microscopic characteristics o…
Motivated by the unique catalytic activity of Cu/ZSM-5 in the decomposition of NO to N 2 + O 2, the redox chemistry of Cu in zeolite ZSM-5 has been studied using FTIR, TPR, EPR, and EXAFS. Isolated ions, Cu 2+, oxocations, [Cu−O−Cu] 2+, and oxide particles have been identified. Their relative abundances depend on the…
We describe the theoretical basis for the exceptionally large molecular first hyperpolarizabilities inherent to (5,15-diethynylporphinato)metal-bridged donor−acceptor (D−A) molecules. β values relevant for hyper-Rayleigh experiments are calculated at 1.064 and 0.830 μm for a complex with such a structure, [5-((4‘-(dim…
The characterization of the coordination geometry of copper ions included within zeolites has been carried out with a combination of in-situ XAFS, photoluminescence, and IR measurements in order to obtain a detailed description of the formation of isolated Cu + monomers with planar 3-coordinate or linear 2-coordinate…
A variety of density-modification techniques are now available for improving electron-density maps in accordance with known chemical information. This modification must, however, always be constrained by consistency with the experimental data. This is conventionally achieved by alternating cycles of map modification i…
Titanium oxide species anchored in the Y-zeolite cavities by an ion-exchange method exhibits a high and unique photocatalytic reactivity for the direct decomposition of NO into N 2, O 2, and N 2 O at 275 K with a high selectivity for the formation of N 2 . The in situ photoluminescence and XAFS (XANES and FT-EXAFS) in…
The high hydroxyl content of mesoporous silicates makes it possible to use them as anchors for the attachment of transition-metal species. In the present study, three different samples corresponding to atomic V/Si ratio of 0.01, 0.05, and 0.10 have been prepared by reacting a silica-based mesoporous matrix of the cubi…
Electronic absorption, fluorescence and fluorescence excitation spectra, and vibrational Raman spectra of selected homogeneous solution phase, free-base tetraaryl-substituted porphyrins specifically, tetraphenylporphine (TPPH 2 ), tetra( p -pyridyl)porphine (TPyPH 2 ), tetra( p - N -methylpyridyl)porphine (TMPyPH 2 ),…