Materials Literature
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The results of an adsorption isotherm investigation of methane on closed-ended single-wall nanotube bundles are presented. The isosteric heat of adsorption was determined as a function of the amount of methane adsorbed on the SWNT substrate for coverages in the first layer. The isosteric heat of adsorption is found to…
The band-edge electronic structure of spherical InP dots under electric fields is investigated using an atomistic pseudopotential approach. Field-induced changes in orbital energies, single-particle wave functions, transition intensities, and excitonic gaps are calculated. We find that interstate couplings profoundly…
Porphyrin dimers were prepared from beta,beta'-dipyrrole derivatives via the double pyrrolylmethylation followed by double [2 + 2] MacDonald porphyrin synthesis.
We present a comparative study of the behavior of electrodes modified with electropolymerized cobalt porphyrins and cobalt phthalocyanine films towards the electro-oxidation of 2-mercaptoethanol (2-ME). First, we report here on the electrochemical formation of the complex-based films and their characterization by cycl…
We study hole intraband relaxation in strongly confined CdSe quantum dots. We observe a dramatic reduction in the hole energy-loss rate in the final stage of hole relaxation at the bottom of the valence band. This reduction occurs because of a significantly increased inter-level spacing near the band edge, and, in par…
Electrical transport properties of intramolecular p–n–p junctions formed on individual semiconducting carbon nanotubes are reported. Chemical dopant “profiling” along the length of a nanotube divides the nanotube into two p-doped sections and a central n-doped section. The double p–n junctions formed on the nanotube d…
Electron injection into nanocrystal thin films is reversibly controlled by applying an electrochemical potential. Complete bleach of the visible interband transition and strong midinfrared intraband absorption are observed upon electron injection into the nanocrystal films. Quenching of the photoluminescence of the na…
We report laser oscillation at ∼610 nm in aggregates of ultrasmall elemental Si nanoparticles. The particles are ultrabright red emitting, dispersed from bulk Si by electrochemistry. The aggregates are excited by radiation at 550–570 nm from a mercury lamp. Intense directed Gaussian beams, with a threshold, manifest t…
In this letter, we report on the integration of epitaxial ferroelectric Pb(Zr, Ti)O3 (PZT) thin films on Si [100] substrates using a SrTiO3 (STO) template layer and a conducting perovskite (La0.5Sr0.5)CoO3 electrode. X-ray diffraction studies reveal both in-plane and out-of-plane alignment of the heterostructure. The…
We identify, by dislocation theory and molecular dynamics simulations, possible dislocation dipoles $(5|7|7|5$ and $4|8|8|4)$ as defect nuclei under tension in boron nitride nanotubes. The formation energies of the dipoles are then evaluated by ab initio gradient-corrected density functional theory. The $5|7|7|5$ dipo…
A convenient microemulsion-mediated hydrothermal process was employed to synthesize ZnO nanowires, which exhibited a strong ultraviolet emission and a relatively weak defect emission. X-Ray diffraction, scanning electron microscopy, transmission electron microscopy and fluorescence spectroscopy were used to characteri…
The ferroelectricity of Bi4Ti3O12 (BIT), (Bi3.2La0.8)Ti3O12 (BLT), Bi4(Ti2.97V0.03)O12 (BTV), and (Bi3.2La0.8)(Ti2.97V0.03)O12 (BLTV) films prepared at 600 °C by metalorganic chemical vapor deposition was compared. For the BIT, BLT, BTV films deposited on (111)Pt/TiO2/SiO2/Si substrates, the ferroelectricity was not o…
We analyze low field hysteresis close to the demagnetized state in disordered ferromagnets using the zero temperature random-field Ising model. We solve the demagnetization process exactly in one dimension and derive the Rayleigh law of hysteresis. The initial susceptibility a and the hysteretic coefficient b display…
The hysteresis properties of ferromagnetic materials at low field are described by the Rayleigh law. We analyze the problem in light of modern statistical mechanics models of hysteresis. In particular, we compute the demagnetization curve and derive the Rayleigh parameters a and b in the random-field Ising model and i…
The modeling of the elastic properties of granular or nanoscale systems requires the foundations of the theory of elasticity to be revisited, as one explores scales at which this theory may no longer hold. The only cases for which a microscopic justification of elasticity exists are (nearly) uniformly strained lattice…
Epitaxial films of an oxide-diluted magnetic semiconductor with rutile structure, Mn-doped SnO2, have been fabricated by pulsed-laser deposition. As the Mn content increases, systematic changes in lattice constants and in-gap absorption are observed. Magnetization measurements show almost paramagnetic behavior. The in…
Photoinduced electron transfer in a size-quantized CdS/TiO2 composite system has been investigated using emission and transient absorption spectroscopy. Quantum-sized CdS and TiO2 particles were synthesized in reverse micelles using di-octyl sulfosuccinate (Aerosol-OT, AOT) as the surfactant stabilizer. The particle s…
Nanoparticles of cerium oxide with a narrow size distribution (±15%) are prepared by mixing cerium nitrate solution with an ammonium reagent. High-resolution transmission electron microscopy (TEM) indicates that over 99% of the synthesized particles are single crystals. TEM and photon absorption are used to monitor pa…
Much effort has been devoted to the study of the formation of superplastic in aluminum alloys on account of its cost and engineering advantages. From a mechanical point of view, the ability of a crystalline material to undergo superplastic behavior is usually linked to a submicrometer grain size. Equal channel angular…
Various kinds of fuels based on alcohols (methanol, ethanol, and isopropanol) and hydrocarbons (methane, ethane, and ethylene) were directly supplied to solid oxide fuel cells (SOFCs) to compare their power generation characteristics. The results on current-voltage characteristics and anodic polarization have revealed…