Materials Literature
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High-performance supercomputing and high-fidelity atomistic methods are used to study the shape effects on the single-particle electronic states of nanocrystals. We found that the shape can be used as an efficient way to control the electronic structures of the nanocrystals. Changing the shape is more flexible and pro…
Motivated by recent measurements of electron paramagnetic resonance (EPR) spectra in modulation-doped CdMnTe quantum wells, [F.J. Teran {\it et al.}, Phys. Rev. Lett. {\bf 91}, 077201 (2003)], we develop a theory of collective spin excitations in quasi-two-dimensional diluted magnetic semiconductors (DMSs). Our theory…
We report a study of the low temperature bulk magnetic properties of the spin ice compound Dy2Ti2O7 with particular attention to the (T < 4 K) spin freezing transition. While this transition is superficially similar to that in a spin glass, there are important qualitative differences from spin glass behavior: the free…
The effect of hole doping on the exchange coupling of the nearest neighbor (NN) Mn pairs in ${\mathrm{Z}\mathrm{n}}_{1\ensuremath{-}x}{\mathrm{M}\mathrm{n}}_{x}\mathrm{T}\mathrm{e}$ is probed by inelastic neutron scattering. The difference in the NN exchange energy $\ensuremath{\Delta}{J}_{1}$ in the presence and in t…
The excited state interaction between CdSe nanocrystals and a hole acceptor, p -phenylenediamine (PPD), is probed using emission and transient absorption spectroscopies. The changes in the photophysical properties of CdSe nanocrystals arising from the interaction with PPD are compared with an aliphatic amine, n -butyl…
The ultrasensitive differential scanning calorimetry is used to observe the glass transition in thin (1-400 nm) spin-cast films of polystyrene, poly (2-vinyl pyridine) and poly (methyl methacrylate) on a platinum surface. A pronounced glass transition is observed even at a thickness as small as 1-3 nm. Using the high…
Silicon nanoparticles with bright visible photoluminescence have been prepared by a new combined vapor phase and solution phase process, using only inexpensive commodity chemicals. CO 2 laser induced pyrolysis of silane was used to produce Si nanoparticles at high rates (20−200 mg/h). Particles with an average diamete…
The electronic energy band structure, density of states (DOS) and charge density contour of KNbO 3 in the paraelectric cubic phase have been studied using the full-potential linearized augmented plane wave method within the generalized gradient approximation for exchange and correlation. The band structure shows an in…
Carbon nanotubes have attracted great interdisciplinary interest because of their unique structure and properties. However, carbon-nanotube research is challenged by several problems, such as: i) mass production of material, ii) control of length, diameter, and chirality, and iii) manipulation for use in diverse techn…
Here we report the synthesis of vancomycin (Van)-capped Au nanoparticles (Au@Van) and their enhanced in vitro antibacterial activities. Au@Van presumably acts as a rigid polyvalent inhibitor of vancomycin-resistant enterococci (VRE). It also has unexpected activity against an E. coli strain. Our results suggest that g…
Abstract Using Slater–Koster tight‐binding calculations, we found that, due to the coexistence of the π–σ electron hybridization and the inter‐tube interactions, the electronic properties of the rope formed by small‐radius metallic zigzag single‐walled carbon nanotubes (SWNTs) have some unique characters: for the rope…
This article discusses the mechanism of nematic liquid crystal alignment in stretched porous polymer films. The polymer films were formed by extreme stretching of an isotropic porous polyolefin, such that the draw ratio was 12:1. A 6-μm-thick porous film with a high porosity coefficient of 92% revealed fine string-sha…
Abstract The Raman spectra of β‐GeS 2 , β‐GeSe 2 , and SnGeS 3 crystals have been investigated as a function of temperature (18 to 300 K) at ambient pressure, and as a function of hydrostatic pressure, up to 4.9 GPa, at room temperature. Our aim was to separate the phonon–excitation–driven (“explicit”) and the thermal…
Abstract Chalcogenide glasses belonging to the Ge x S 94 − x Bi 6 system (14 ≤ x ≤ 28.33 at%) have been prepared from high purity constituent elements. Thin films of the same materials have been deposited by vacuum thermal evaporation. Optical absorbance measurements have been performed on the as‐deposited films. The…
Once spilled into soils, dense nonaqueous phase liquids (DNAPLs) such as chlorinated solvents migrate deep into the subsurface because of their high density. Their downward migration typically continues until capillary forces balance gravitational forces or until essentially impermeable strata are reached. Efforts to…
The structure and morphology of nanosized Cu islands grown by sputter deposition on clean SiO2 substrates and Ti-underlayered SiO2 substrates are investigated using transmission electron microscopy. On SiO2, spherical Cu islands with a random crystalline orientation are formed, whereas on Ti/SiO2, semispherical island…
Transparent ferroelectric strontium–barium niobate (SBN) doped silica nanocomposites were prepared via a modified sol–gel process. Their structural properties were characterized by x-ray diffraction and Raman spectroscopy. It was found that by annealing the nanocomposites at temperatures between 600 and 800 °C, pure t…
A method to study temperature dependent thickness variation of thin films has been developed based on angle and energy dispersive x-ray reflectivity (EDR) techniques. The data analysis scheme developed for this method combines both energy and angle dispersive x-ray reflectivity (ADR) profiles. The ADR technique provid…
We study the phase resonances in metallic compound gratings. The diffraction problem is solved by means of the modal method and the surface impedance boundary condition. The response of gratings made of various metals is analysed. Curves of specular efficiency, field amplitude and phase inside the grooves are shown an…
The magnetic order resulting from an indirect exchange between magnetic moments provided by the spin-polarized hole gas in the metallic phase of a ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}$ double layer structure is studied via Monte Carlo simulation. The exchange is calculated to the second order…