Materials Literature
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A theory of collective plasma excitations in a linear periodic array of multishell nanotubes is presented. The electron system in the nanotubes is modeled by a quasifree electron gas confined to the surface of an infinitely long cylinder. The plasmon dispersion equation is derived in the random-phase approximation neg…
A new terminally protected synthetic tripeptide with noncoded amino acids, tert-butyloxycarbonyl-β-alanyl-α-aminoisobutyryl-β-alanyl methyl ester, is synthesized. The product is characterized by 1H NMR and DQF COSY NMR data. This tripeptide produces thermoreversible gels in 1,2-dichlorobenzene (DCB) at room temperatur…
Photoreflectance spectra of a high-quality ZnO epilayer on the ScAlMgO4 (0001) substrate grown by laser molecular-beam epitaxy exhibited clear excitonic resonances due to three excitons associated with uppermost valence bands (A, B, and C excitons). The oscillator strengths of the B and C excitons are larger than that…
We report on the properties of lanthanum-doped SrTiO3 thin films grown by off-axis laser ablation on LaAlO3 and SrTiO3 substrates in oxygen partial pressures ranging from 10−8 Torr to 55 mTorr. The La/Sr doping ratio of the ablation target was 1%. The resulting films have carrier densities measured in the range of 4.7…
We describe a thermoelectric device structure that confines the thermal gradients and electric fields at the boundaries of the cold end, and exploits the reduction of thermal conductivity at the interfaces and the poor electron-phonon coupling at the junctions. The measured temperature–current and voltage–current char…
The photoinduced non-oxidative methane coupling at room temperature was examined by using a series of silica-alumina samples prepared by a sol–gel method, in order to clarify the photoactive sites of silica-alumina. The maximum yield of ethane, the main product in this reaction condition, was obtained on the sample co…
Electronic properties of ferroelectric SrBi2Ta2O9 (SBT) SrBi2Nb2O9 (SBN) and PbBi2Nb2O9 (PBN) have been investigated using a first-principles calculational method with optimized structures. In optimized SBT, the displacement of Ta in TaO6 octahedra is small, while the displacement of Nb in NbO6 octahedra is larger in…
The distribution of gallium/germanium in the type-I clathrates Sr8Ga16Ge30 and Sr4Eu4Ga16Ge30 over the three crystallographically distinct framework sites has been determined by resonant diffraction. The analyses indicate a strong preference for the occupation of the 6c site by gallium. This is consistent with theoret…
In this study, a technique is presented for developing constitutive models for polymer composite systems reinforced with single-walled carbon nanotubes (SWNT). Because the polymer molecules are on the same size scale as the nanotubes, the interaction at the polymer/nanotube interface is highly dependent on the local m…
To understand and improve the applications of titanium-oxide nanoparticles, it is extremely important to perform a detailed investigation of the surface and the interior structural properties of nanocrystalline materials, such as rutile and anatase with diameter of few nanometers. Here, x-ray absorption spectroscopy h…
Two molecular triads consisting of a porphyrin (P) covalently linked to a fullerene electron acceptor (C60) and a π-extended tetrathiafulvalene electron donor (TTF) have been synthesized. Time resolved spectroscopic investigations of the triad featuring a free base porphyrin moiety (TTF–P2H–C60) show that in 2-methylt…
A new Monte Carlo algorithm is implemented for simulation of the density of states of free-standing polymer films. The algorithm combines the original idea of conducting a random walk in energy space with advanced trial moves such as configurational bias and end-bridging. Excellent agreement is found between the resul…
White electroluminescence (EL) was observed from hydrogenated amorphous-SiNx-based light-emitting device. Silicon nitride thin films were deposited on the indium-tin-oxide (ITO)-coated glass substrate by plasma enhanced chemical vapor deposition method with a mixture of Ar-diluted 5% SiH4 and pure N2 gases, in the rat…
We study the equilibrium behavior and dynamics of a polymer collapse transition for a system composed of a short Lennard-Jones (LJ) chain immersed in a LJ solvent for solvent densities in the range of ρ=0.6–0.9 (in LJ reduced units). The monomer hydrophobicity is quantified by a parameter λ∈[0,1] which gives a measure…
The kinetic interplay between crystal superstructure growth and late-stage liquid phase coarsening in a polymer blend has been examined. By controlling the relative quench depths for liquid–liquid phase separation and crystallization, the growth kinetics of the characteristic length scales of the simultaneous ordering…
A mode-coupling theory for dense polymeric systems is developed which unifyingly incorporates the segmental cage effect relevant for structural slowing down and polymer chain conformational degrees of freedom. An ideal glass transition of polymer melts is predicted which becomes molecular-weight independent for large…
We use dynamical low-energy electron diffraction (LEED) to determine the surface structure of $\ensuremath{\alpha}\ensuremath{-}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}(0001).$ Sapphire surfaces are prepared in three different ways, and the diffraction results are analyzed using an exhaustive search of possible models. For a…
Surfaced-enhanced Ramon scattering (SERS) spectra of pyrazine are analyzed on the basis of the properties of the electronic states of the metal-adsorbate surface complex. Ab initio CIS calculations have been carried out for the Ag2-pyrazine complex, which have enabled us to find two excited singlets, namely CT0;1B1 an…
Carbon nanostructures of different kinds have been synthesized by chemical vapor deposition. By modifying the deposition temperature, the catalyst material, and the hydrocarbon, nanofibers with herringbone structure, multi-walled nanotubes with tubular structure, and single-walled nanotubes were deposited. The nanostr…
We have studied the oxygen-isotope effects on T_{c} and in-plane penetration depth λ_{ab}(0) in an optimally doped 3-layer cuprate Bi_{1.6}Pb_{0.4}Sr_{2}Ca_{2}Cu_{3}O_{10+y} (T_{c} \sim 107 K). We find a small oxygen-isotope effect on T_{c} (α_{O} = 0.019), and a substantial effect on λ_{ab} (0) (Δλ_{ab} (0)/λ_{ab} (0…