Materials Literature
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The optical and electrochemical properties of transparent, boron-doped diamond thin film, deposited on quartz, are discussed. The films were deposited by microwave-assisted chemical vapor deposition, for 1-2 h, using a 0.5% CH4/H2 source gas mixture at 45 Torr and 600 W of power. A high rate of diamond nucleation was…
Homocrystallized and amorphous enantiomeric blend films were prepared from the melt of high molecular weight poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) (1:1) by crystallization and quenching, respectively. A phosphate-buffered solution was used to investigate effects of homocrystallinity via in vitro hydrolysis…
Rates of Diels-Alder cycloaddition of anthracenes with p-benzoquinone and its derivatives as well as rates of hydride-transfer reactions from 10-methyl-9,10-dihydroacridine to the same series of p-benzoquinones are accelerated significantly in the presence of metal ions in acetonitrile. An extensive comparison of the…
The introduction of highly intense wiggler and undulator beamlines has reintroduced the problem of X-ray radiation damage in protein crystals even at cryogenic temperatures. Several metrics for monitoring radiation damage are considered and unit-cell volume expansion is systematically investigated using crystals of th…
Radiation-induced degradation of protein or DNA samples by synchrotron radiation is an inherent problem in X-ray crystallography, especially at the 'brighter' light sources. This short review gives a radiation chemical perspective on some of the physical and chemical processes that need to be considered in understandi…
Density-functional theory is used to examine aspects of the copper vacancy (VCu) in cuprous oxide (Cu2O). The normal vacancy configuration, obtained by simple removal of a Cu atom from the lattice, is found to be 0.1 eV higher in energy than a split vacancy configuration wherein a nearby Cu atom is displaced toward a…
Arrays of ${\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Co}}_{x}$ $(0.0<~x<~1.0)$ nanowires have been fabricated by codepositing Fe and Co into porous anodic alumina. Transmission electron microscope results show that the nanowires are regular and uniform, about $7.5\ensuremath{\mu}\mathrm{m}$ in length and $20\math…
Inhomogeneous polymer-dispersed liquid crystal devices having gradient droplet distribution were fabricated and their phase retardation characterized. The gradient refractive index profile can be used as switchable prism gratings, and positive and negative lenses with tunable focal lengths. Such a tunable electronic l…
An "S"-shaped chiral motif of a p-xylylene-bridged bis(cyclic dipeptide) (1), having four hydrogen-bonding amide functionalities, formed a homochiral supramolecular polymer in solution. X-ray crystallography of a slightly modified version of 1 for an enhanced crystallinity showed one-dimensional columnar assemblies vi…
In this paper we present a Raman-scattering study of the phase transitions in the ${\mathrm{PbZr}}_{1\ensuremath{-}x}{\mathrm{Ti}}_{x}{\mathrm{O}}_{3}$ systems around the morphotropic phase boundary over a wide temperature range. The boundary between rhombohedral and monoclinic phases was found to be a quasivertical l…
The presence of various counteranions at the interfacial region of the silicate-surfactant mesophase introduces opportunities for manipulation of the phase structure. Well-ordered 3D-hexagonal P63/mmc, cubic Pmn, 2D-hexagonal p6mm, and cubic Iad mesoporous materials have been synthesized with the same surfactant, cety…
The structures and temperature-dependent photoluminescence properties of the one-dimensional compounds [(TPA)(2)Au][Au(CN)(2)], 1, and (TPA)AuCl, 2, are reported. An extended linear chain with weak Au.Au interactions along the c-axis is evident in the structure of 1, and a helical chain with a pitch of 3.271 A is seen…
Network polymers exhibiting large surfaces areas (900-1000 m2g-1) are prepared by the highly efficient dibenzodioxane forming reaction between meso-tetrakis(pentafluorophenyl)porphyrin and a rigid bis(catechol) monomer.
Some of the most regular porous silicates (MCM-41 and SBA-15), with several different pore diameters from 2.4 to 8.7 nm, are used to study the van der Waals fragile liquid toluene in confined geometry. We measure two major macroscopic signatures of a glass transition, i.e., a discontinuous change in the heat capacity…
Lattice vibrations and dielectric properties of the anatase phase of titanium dioxide are investigated from a theoretical perspective. A first-principles pseudopotential band calculation based on density-functional perturbation theory is performed to evaluate normal vibrations, dielectric tensors, and Born effective c…
Thermoelectric properties, i.e., thermal conductivity, electrical conductivity, and the Seebeck coefficient, have been measured in the directions parallel (in-plane) and perpendicular to the interface of an n-type Si(80 Å)/Ge(20 Å) superlattice. A two-wire 3ω method is employed to measure the in-plane and cross-plane…
An improved process is presented to functionalize carbon nanotubes by potassium permanganate with the help of phase transfer catalyst (PTC). The PTC helps to extract potassium permanganate from the solid phase to an organic solvent phase and improves the efficiency of nanotube oxidation. The higher reaction efficiency…
This study describes the relative effect on the permanent magnet characteristics viz. remanence (Br), intrinsic coercivity (Hci), Curie temperature (TC), and rectangularity of the intrinsic demagnetization curve, when Al, Cu, Ga, and Nb are added individually to NdFeB. Each elemental addition causes significant improv…
Organic-inorganic hybrids are an important class of new materials that offer improved thermal and mechanical properties over normal polymers. They may be produced by either the sol-gel route or through the use of inorganic compounds possessing reactive functional groups. Polyhedral oligosilsesquioxanes (POSS) are comp…
We show that one-dimensional topological objects (kinks) are natural degrees of freedom for an antiferromagnetic Ising model on a triangular lattice. Its ground states and the coexistence of spin ordering with an extensive zero-temperature entropy can be easily understood in terms of kinks forming a hard-sphere liquid…