Materials Literature
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Grain-boundary and surface scattering are known to increase the electrical resistivity of thin metallic films and wires. The length scale at which these produce appreciable effects is of the order of the electronic mean free path. For the well-studied case of thin films, both mechanisms can, in principle, be used to e…
High-resolution core- and valence-level photoemission spectra of Nb-doped ${\mathrm{TiO}}_{2}$ ceramics $({\mathrm{Ti}}_{1\ensuremath{-}x}{\mathrm{Nb}}_{x}{\mathrm{O}}_{2}$ with $0.01<x<0.8)$ have been measured using monochromatic x-ray excitation. Nb doping produces a well-defined photoemission peak in the bulk…
Controlled growth of molecular magnets, in terms of their size, shape, and organization, is demonstrated with a model cyanometallate, Prussian blue crystals. The TEM image shows the hydrophobic cubic nanoparticles (scale bar 100 nm), prepared in a microemulsion and encapsulated in a shell of surfactant, which readily…
At semiconductor-metal junctions, the Schottky barrier height is generally fixed by "Fermi-level pinning." We find that when a semiconducting carbon nanotube is end contacted to a metal (the optimal geometry for nanodevices), the behavior is radically different. Even when the Fermi level is fully "pinned" at the inter…
We perform density-functional calculations to search for hydrogen adsorption sites and predict maximum storage capacity in single-walled carbon nanotubes. We find two chemisorption sites at top sites of the exterior and the interior of the tube wall. We further find that a form of H2 molecule can exist in an empty spa…
A temperature-dependent, single crystal x-ray diffraction study of the giant magnetocaloric material, ${\mathrm{Gd}}_{5}({\mathrm{Si}}_{2}{\mathrm{Ge}}_{2})$, across its Curie temperature (276 K) reveals that the simultaneous orthorhombic to monoclinic transition occurs by a shear mechanism in which the $(\mathrm{Si},…
We report the preparation of highly monodisperse ZnO nanoparticles using poly(vinyl pyrrolidone) (PVP) as the capping molecules. The surface-modified ZnO nanoparticles were found to be remarkably stable. The optical absorption shows distinct excitonic features. Markedly enhanced near-band-edge ultraviolet photolumines…
New methods have been developed in recent years that are now being successfully applied in the preparation of pillared interlayered clays (PILCs). Variations in the procedures concern different parameters involved in the synthesis, such as the starting clay, the intercalating solution, the intercalation process, and t…
First principles density functional calculations of the electronic and magnetic properties of the layered oxide ${\mathrm{NaCo}}_{2}{\mathrm{O}}_{4}$ have been performed using the general potential linearized augmented plane wave method. The electronic transport properties are discussed in terms of the calculated para…
We probe the influence of grating effects on plasmon excitations in gold nanoparticles arranged in regular two-dimensional patterns. Samples produced by electron-beam lithography are investigated by femtosecond time-resolved and spectroscopic methods. We find a strong dependence of the plasmon lifetime and resonance w…
The infrared spectral performance of the N x O y species observed on oxide surfaces [N2O, NO−, NO, (NO)2, N2O3, NO+, NO2 − (different nitro and nitrito anions), NO2, N2O4, N2O5, NO2, and NO3 − (bridged, bidentate, and monodentate nitrates)] is considered. The spectra of related compounds (N2, H-, and C-containing nitr…
Multiwall carbon nanotubes have been dispersed homogeneously throughout polystyrene matrices by a simple solution-evaporation method without destroying the integrity of the nanotubes. Tensile tests on composite films show that 1 wt % nanotube additions result in 36%–42% and ∼25% increases in elastic modulus and break…
Combining equilibrium and nonequilibrium molecular dynamics simulations with accurate carbon potentials, we determine the thermal conductivity lambda of carbon nanotubes and its dependence on temperature. Our results suggest an unusually high value, lambda approximately 6600 W/m K, for an isolated (10,10) nanotube at…
The model and theoretical understanding of the Raman spectra in disordered and amorphous carbon are given. The nature of the G and D vibration modes in graphite is analyzed in terms of the resonant excitation of \ensuremath{\pi} states and the long-range polarizability of \ensuremath{\pi} bonding. Visible Raman data o…
The specific heat of the perovskite manganite La0.78Pb0.22MnO3-d was measured from 0.5 to 25 K. The results yield values of the electronic density of states, the Debye temperature, and the spin-wave stiffness constant of the compound. The magnetic contribution was found to be consistent with the existence of a gap in…
The kinetics of the thermal decomposition of tin tetrachloride has been studied experimentally and theoretically. Ab initio MO calculations showed that SnCl 4 finally decomposed into Sn( 3 P) and four chlorine atoms through four subsequent Sn−Cl bond dissociation channels. Two sets of kinetic experiments were performe…
A novel class of supramolecular assemblies in organic media consisting of a molecular wire of a halogen-bridged platinum complex [Pt(en)2][PtCl2(en)2]4+ (en = 1,2-diaminoethane) and anionic amphiphiles is developed. When double-chained phosphates or sulfonates are employed, the resultant [Pt(en)2][PtCl2(en)2](4+)-lipi…
The in-plane oxygen vibrations in La 2 NiO 4 are investigated for several hole-doping concentrations both theoretically and experimentally via inelastic neutron scattering. Using an inhomogeneous Hartree-Fock plus random-phase approximation numerical method in a two-dimensional Peierls-Hubbard model, it is found that…
Electron paramagnetic resonance (EPR) investigations of the ordering behaviour in single crystals of Cr 3+ -doped dimethylammonium aluminium sulphate hexahydrate (DMAAS) are presented at the transition from the ferroelastic to the ferroelectric phase. The measurements on chromium-doped DMAAS show that the Cr 3+ probe…
The NH tautomerism of five Mg-free chlorophyll a and b derivatives 2-6 was studied utilizing NMR spectroscopy and molecular modeling. The results from the dynamic NMR measurements of the chlorins revealed that substituent effects contribute crucially to the free energy of activation (DeltaG(double dagger)) in the NH t…