Materials Literature
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Flexible, swellable organosilica tubes are the most remarkable new mesophase generated by co-hydrolysis of tetraalkylammonium-substituted trimethoxysilanes and TEOS. The composites self-organize into lamellar layers or hexagonal tubules, whose elastic walls allow the uptake of anionic or lipophilic species. The hexago…
Based on the optic and dielectric data acquired under different mechanical and electric conditions and temperature, we show that an orthorhombic phase exists near the morphotropic phase boundary (MPB) (on both the rhombohedral and tetragonal sides of MPB). Because of the proximity of the free energy of this phase to t…
The treatment of [Ln(hfac)3(H2O)2] (Ln(III) = Y, Nd–Lu) with IM-2py (2-(2-pyridyl)-4,4,5,5-tetramethyl-1H-imidazolyl-1-oxyl) readily gave a series of novel rare earth or lanthanide radical complexes [Ln(hfac)3(IM-2py)]. The molecular structures of the Sm, Gd, Dy, Er and Yb complexes have been determined to be bicapped…
Bahamian soft marine stromatolites consist of cyanobacterial biofilms and carbonate sand grains (ooids) embedded in their extracellular polymeric secretions (EPS). EPS were isolated from natural marine stromatolites and the laboratory cultured stromatolite forming cyanobacterium isolate Schizothix sp. Laboratory inves…
Abstract The results of an interlaboratory or round‐robin experiment in high‐temperature gel permeation chromatography (HT‐GPC) analysis are presented. The intention was to determine and raise awareness of interlaboratory reproducibility of HT‐GPC techniques. Fifteen laboratories performed analyses of five polyethylen…
In this study, the interface structure of α-Fe/Nd2Fe14B nanocomposite magnets has been investigated by employing both the positron lifetime spectroscopy and the two-detector Doppler broadening measurements of the positron–electron annihilation γ quanta. Positron lifetime studies show that there are two kinds of interf…
Phosphorus species could be grafted onto the surface of Si-MCM-41 by simply treating Si-MCM-41 with phosphoric acid for a very short period, followed by high temperature calcination. The existence and state of surface phosphorus species grafted on Si-MCM-41 are confirmed by XPS measurement. Using XRD and N2 adsorption…
Crystalline films on the surface of a polypyrrole (see Figure for SEM image) are obtained electrochemically from cobalt(bis-dicarbolide)-doped polypyrrole in aqueous Bu4N+Cl–, or (less effectively) in Bu4P+Cl– solution. The films, which are unidirectional (inwards) cation barriers, are highly stable in aqueous media,…
Structured silicates/fluorinated polyimide nanocomposites display excellent water-absorption retardation behavior. This leads to lower leakage-current densities and lower dielectric constants under higher humidity conditions than those of the pristine fluorinated polyimides. Part of the chemical structure of the layer…
The effect of pore size and uniformity on the response of nanoporous alumina, formed on aluminum thick films through an anodization process, to ammonia and humidity at room temperature is reported. Pore sizes examined range from 13 nm to 48 nm, with pore size standard deviations ranging from 2.6 nm to 7.8 nm. The resp…
Barium strontium titanate thin films were deposited by sputtering on Pt/SiO2 structures using five different host substrates: magnesium oxide, strontium titanate, sapphire, silicon, and vycor glass. These substrates were chosen to provide a systematic change in thermal strain while maintaining the same film microstruc…
We report on photoluminescence (PL) spectra of ZnO films grown by low pressure metalorganic vapor phase epitaxy. For PL measurements, high quality ZnO thin films were epitaxially grown on Al2O3(0001) substrates. Time-integrated PL spectra of the films at 10 K clearly exhibited free A and B excitons at 3.376 and 3.382…
Functionalized large-pore mesoporous SBA-15 is utilized for the first time as a good substrate in high performance liquid chromatography (HPLC) to separate biomolecules including peptides and proteins.
We studied the changes in the electronic structure of ${\mathrm{LaNiO}}_{3\ensuremath{-}\ensuremath{\delta}}$ across the metal-insulator transition. The technique used in the study was mainly $\mathrm{O} 1s$ x-ray absorption spectroscopy (XAS). The experimental spectrum of ${\mathrm{LaNiO}}_{3.00}$ was analyzed in ter…
We study the low-temperature dynamics of a shallow donor, e.g., $^{31}$P, impurity electron spin in silicon, interacting with the bath of nuclear spins of the $^{29}$Si isotope. For small applied magnetic fields, the electron spin relaxation is controlled by the steady state distribution of the nuclear spins. We calcu…
The reactive conversion of biosilica meso- and nanostrucures into new compositions with retention of shape and fine features is demonstrated. The shape-preserving nature of the chemical conversion process is illustrated for the reaction of silica-based diatom frustules with Mg gas to form MgO (see Figure). This techni…
We report here on studies examining the use of fibrin as an alternative to collagen for the entrapment of neonatal aortic rat smooth muscle cells (SMCs) in the fabrication of media equivalents. The studies show increased collagen production by fibroblasts entrapped in fibrin, which suggests that fibrin may be used in…
We compare the field emission characteristics of dense (109 nanofibers/cm2), sparse (107 nanofibers/cm2), and patterned arrays (106 nanofibers/cm2) of vertically aligned carbon nanofibers on silicon substrates. The carbon nanofibers were prepared using plasma-enhanced chemical vapor deposition of acetylene and ammonia…
We study the influence of nitrogen, a potential acceptor in ZnO, on the lattice dynamics of ZnO. A series of samples grown by chemical vapor deposition (CVD) containing different nitrogen concentrations, as determined by secondary ion mass spectroscopy (SIMS), was investigated. The Raman spectra revealed vibrational m…
ZnO micropatterning under very mild conditions is presented. Photolysis (using a mask) of Si–C bonds in a self-assembled phenylsilane layer yields a patterned phenyl/hydroxy surface. ZnO is selectively deposited at 55 °C on the phenyl domains by electroless deposition using a Pd catalyst adhered to the surface. The vi…