Materials Literature
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Vanadium oxide nanotubes were synthesized as the main product by hydrothermal self-assembling from ammonium metavanadate (NH(4)VO(3)) and organic molecules as structure-directing templates. Several kinds of templates including primary amines (C(n)H(2n+1)NH(2)), alpha,omega-diamines (H(2)N[CH(2)](n)NH(2)), and quaterna…
It is demonstrated that an isotropic left-handed medium can be constructed as a photonic structure consisting of two dielectric materials, one with positive and another with negative dielectric permittivities epsilon. Electromagnetic waves supported by this structure are the surface waves localized at the dielectric i…
Stable solutions of conjugated poly(phenylene vinylene)s and poly(phenylene ethynylene)s in nematic liquid crystals are reported. The polymers all contain triptycene units fused into their backbones to obtain the high solubility needed to maintain solubility in complex liquid crystalline media. The polymer backbones a…
We describe the preparation and characterization of core−shell latex particles, consisting of a polystyrene core, covered with a perfluoroalkyl acrylate shell. The core−shell particles were prepared by a two-stage emulsion polymerization under kinetically controlled conditions and were characterized by transmission el…
We have determined the Ti and O components of the rutile TiO2 valence band using the method of site-specific x-ray photoelectron spectroscopy. Comparisons with calculations based on pseudopotentials within the local density approximation reveal the hybridization of the Ti 3d, 4s, and 4p states, and the O 2s and 2p sta…
Negative differential conductance (NDC) is expected to be an essential property to realize fast switching in future electronic devices. We here present a thorough analysis on electron transportability of a simple atomic-scale model consisting of square prisms, and clarify the detailed mechanism of the occurrence of ND…
The quasiclassical theory of a nanosize point contacts (PC) between two ferromagnets is developed. The maximum available magnetoresistance values in PC are calculated for ballistic versus diffusive transport through the area of a contact. In the ballistic regime the magnetoresistance in excess of few hundreds percents…
Using the spectral approach, we analyze the effective properties of a composite which deviates slightly from periodicity. We find that, when the inclusions are randomly displaced from their equilibrium positions, the sharp resonances seen in the periodic case are broadened, and an additional branch cut appears. We use…
We calculate the quantized conductance of nanosize point contacts between two ferromagnets for different mutual orientations of the magnetic moments. It is found that the magnetoresistance MR is a multivalued function of the quantized conductance at the parallel alignment of the magnetizations sigma^F. This leads us t…
A new scalable method for purification of single-wall carbon nanotubes (SWNTs) by using microwave heating in air is developed. The microwaves couple to the residual metal catalyst, raising significantly the local temperature leading to both the oxidation and rupturing of the carbon passivation layer over the metal cat…
Biologically active semiconductor quantum dot (QD)-labeled polystyrene (PS) beads with tailored QD loading and luminescence have been prepared via the layer-by-layer (LbL) assembly approach. PS beads of 925 nm diameter were used as templates for the deposition of CdTe nanocrystal/polyelectrolyte (PE) multilayers, form…
Truncated triangular silver nanoplates have been synthesized in large quantities using a solution phase method in the presence of cetyltrimethylammonium bromide micelles. The obtained particles have an average edge size of 68 nm, thickness of 24 nm, and the degree of truncation of 0.35. They are single crystals, with…
Fluorescence has been observed directly across the band gap of semiconducting carbon nanotubes. We obtained individual nanotubes, each encased in a cylindrical micelle, by ultrasonically agitating an aqueous dispersion of raw single-walled carbon nanotubes in sodium dodecyl sulfate and then centrifuging to remove tube…
Exciton luminescence was investigated in La-doped BaF2 crystals. Two luminescence bands at 4.26 and 3.82 eV related to excitons have been observed. The excitation spectrum of the 4.26 eV band of BaF2–LaF3 was similar to that of the exciton emission band of pure BaF2 crystals. The excitation spectrum of the 3.82 eV ban…
The title compound, C18H18N4, lies on an inversion center. The benzimidazolyl moiety is essentially planar. Intermolecular N—H⋯N hydrogen bonds give rise to an infinite helical chain structure, with the chains stacked by C—H⋯π and π⋯π interactions.
Quantum confinement effect has been the dominant approach guiding the search for light-emitting silicon. By first-principles total energy calculations of Si delta-doped with oxygen layers, however, we show that this generally accepted mechanism is ineffective. Instead, a different mechanism is proposed based on defect…
Lithium ions were electrochemically inserted into V 2 O 5 ·0.5H 2 O xerogel and studied with 7 Li magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. Two distinct lithium environments were resolved and assigned to lithium ions occupying either interfacial or intercalated sites in the V 2 O 5 ·0.5…
The site occupancy of hydrogen in Nb(74 at. %)-Mo(26 at. %) alloys is investigated at room temperature for hydrogen concentrations 0.016, 0.026, and 0.059 in the hydrogen--metal-atom ratio $([\mathrm{H}]/[M])$ by the channeling method utilizing a nuclear reaction ${}^{1}\mathrm{H}{(}^{11}\mathrm{B},\ensuremath{\alpha}…
The oxygen nonstoichiometry, transport properties, and structure stability of ZrO 2 -promoted SrCo 0.4 Fe 0.6 O 3 - δ (SCFZ) were investigated. The nonstoichiometry of SCFZ increased with increasing temperatures and decreasing oxygen partial pressures. The results of X-ray diffraction and oxygen desorption experiments…
Cubic boron nitride is synthesized from a hexagonal graphitic phase, the synthesis conditions being affected by chemical or intrinsic defects. The electronic contribution to this defect dependence is investigated using an ab initio local-density approach for the simple defects B, C, N, and O. Energy differences betwee…