Materials Literature
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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…
Poly(γ-benzyl- l -glutamate) (PBLG) is a synthetic polypeptide with a rigid helical conformation in several solvents. Small-angle X-ray and neutron scattering measurements were used to study the reversible gelation process in semidilute isotropic solutions of PBLG in benzyl alcohol. Time-resolved measurements of the s…
Carbon nanotubes (CNTs) are an interesting class of nanostructures which can be thought of as arising from the folding of a layer of graphite (a graphene sheet) to form a hollow cylinder composed of carbon hexagons. However, practical applications are still limited by the intricate process of synthesis and the inabili…
Alanyl-alanine-derived poly(isocyanide)s possess a helical structure that persists even in aqueous media. These rigid macromolecules possess a regular distribution of carboxylic acid-terminated side chains which for the first time allows the study of the templating process involved in biomineralization using a shape-p…
The synthesis, structural characterisation and preliminary magnetic studies of a Co12 wheel are reported; the magnetic investigations reveal that the electronic ground state has a spin S = 6, which corresponds to ferromagnetic interactions between the twelve Co(II) ions.
We have investigated systematically the effects of various gas adsorbates (H2, N2, O2, and H2O) on the electronic structures and the field emission properties of open edges of single-walled carbon nanotubes by density functional calculations. All of the molecules, except N2, dissociate and chemisorb on open nanotube e…
We report here, for the first time, synthesis of anchored Pd complexes in mesoporous supports such as MCM-41 and MCM-48 as true heterogeneous catalysts for hydrocarboxylation of aryl olefins and alcohols to give excellent conversion ( approximately 100%) and regioselectivity ( approximately 99%) for 2-arylpropionic ac…
Modification induced by 110 MeV Ni ion irradiated thin film samples of C60 on Si and quartz substrates were studied at various fluences. The pristine and irradiated samples were investigated using Raman spectroscopy, electrical conductivity and optical absorption spectroscopy. The Raman data and band gap measurements…