Materials Literature
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Recent experiments on several oxide perovskites reveal that they undergo tilt phase transitions to higher-symmetry phases on increasing pressure and that dTc/dP<0, contrary to a general rule previously proposed for such zone-boundary transitions. We show that the negative slope of the phase boundary is a consequence o…
Surface and ferroelectric properties of ${\mathrm{PbTiO}}_{3}$ thin films are investigated using an interatomic potential approach with parameters determined from first-principles calculations. We show that a model developed for the bulk describes properly the surface properties of ${\mathrm{PbTiO}}_{3}$. In particula…
Experiments and three-dimensional numerical modeling of nanoscale piezoelectric response across a single domain wall in ferroelectric lithium niobate are presented. Surprising asymmetry in the local electromechanical response across a single antiparallel ferroelectric domain wall is reported. Piezoelectric force micro…
We investigate the effect of orbital overlap on optical matrix elements in empirical tight-binding models. Empirical tight-binding models assume an orthogonal basis of (atomiclike) states and a diagonal coordinate operator which neglects the intra-atomic part. It is shown that, starting with an atomic basis which is n…
Ammonia adsorption on single-walled carbon nanotubes (SWNTs) was studied by means of infrared spectroscopy at both cryogenic (approximately 94 K) and room (approximately 300 K) temperatures. At 94 K, vacuum-annealed SWNTs showed no detectable ammonia uptake. However, the ammonia adsorption was found to be sensitive to…
Uniaxial strain is induced by pushing single-wall carbon nanotubes (SWNTs) with an atomic force microscope tip. The vibrational and electronic energies of nanotubes are found to be very sensitive to strain. For both metallic and semiconducting SWNTs under strain, the $D$, $G$, and ${G}^{\ensuremath{'}}$ band Raman mod…
An all-perovskite solid oxide fuel cell has been achieved using LSCM ((La0.75Sr0.25)0.95Cr0.5Mn0.5O3–δ) as the anode, LSGMCo (La0.8Sr0.2Ga0.8Mg0.15-Co0.05O3–δ) as the electrolyte, and GSC (Gd0.4Sr0.6CoO3–δ) as the cathode (see Figure). The all-perovskite design enhances structural integrity and minimizes interface pol…
The surface structure of silica glasses has been simulated using molecular dynamics. The surface hydroxyl concentration was estimated to be 4.5/nm 2 , based on surface defect statistics. Hydroxyl‐silica potentials were developed and used to study the hydroxylation of silica surface. It is found that the energy of chem…
A new molecular motor is conceptually constructed from a double-walled carbon nanotube (DWNT) consisting of a long inner single-walled carbon nanotube (SWNT) and a short outer SWNT with different chirality. The interaction between inner and outer tubes is the sum of the Lennard-Jones potentials between carbon atoms in…
Following enzyme adsorption within the pores of mesoporous silica template spheres, polypeptide multilayers are assembled on the particles, and the template is dissolved. This yields a high concentration of enzyme in an active state within the microcapsules (microcapsules are shown in the Figure), which can be release…
Cores to celebrate: At 370 °C, [email protected] core–shell nanoparticles rapidly alloy but the reciprocal core–shell nanoparticles, [email protected] (see STEM images, left: Cu spectral map; middle: Pt spectral map; right: bright-field image), are kinetically stabilized and show high activity and selectivity for NO r…
Innen oder außen macht einen Unterschied: Bei 370 °C bilden Pt@Cu-Kern-Schale-Nanopartikel rasch eine Legierung, während die reziproken Kern-Schale-Nanopartikel Cu@Pt (siehe STEM-Bilder: links Cu-Spektralkarte, Mitte Pt-Spektralkarte, rechts Hellfeldbild) kinetisch stabilisiert sind und bei der NO-Reduktion hoch aktiv…
Quantum dots with a core/shell/shell structure consisting of an alloyed core of InAs(x)P(1-x), an intermediate shell of InP, and an outer shell of ZnSe were developed. The InAs(x)P(1-x) alloyed core has a graded internal composition with increasing arsenic content from the center to the edge of the dots. This composit…
A Zn-containing perovskite structure of composition Ba0.5Sr0.5Zn0.2Fe0.8O3–δ is proposed as an oxygen-transport material with good phase stability at low oxygen partial pressures at temperatures up to 950 °C. The material has been successfully tested in a membrane reactor in the partial oxidation of methane to synthes…
We present a general model study of surface-enhanced resonant Raman scattering and fluorescence, focusing on the interplay between electromagnetic (EM) effects and the molecular dynamics as treated by a density matrix calculation. The model molecule has two electronic levels, is affected by radiative and nonradiative…
Abstract A new class of main‐chain liquid‐crystalline photodimerizable vanillylidene‐containing alkylpolyphosphate esters were synthesized from 2,5‐bis[ m ‐hydroxyalkyloxy(vanillylidene)] cyclopentanones with various alkylphosphoro‐ dichloridates by solution polycondensation in chloroform at ambient temperature. Their…
Abstract In addition to the model compounds 4a and 4b , the dendrimers 11 and 14 with trans ‐stilbene chromophores in the core and on the periphery of the dendrons were prepared and their photochemistry was studied in solution and in neat films. Due to the flexibility of the arms, intramolecular and intermolecular CC…
A novel field emission pressure sensor has been achieved using carbon nanotube (CNT) arrays as the field emitters. The sensor consists of the anode elastic membrane fabricated by wet etching process and a multi-wall carbon nanotube array cathode in the micro-vacuum cavity. The prototype pressure sensor has a measured…
We describe an electrochemical cell containing a single faradic electrode (a Pt ultramicroelectrode) and a blocked (polarized) electrode (Si with an insulating SiO2 film) that served as a capacitive counter electrode. When a bias was applied between the two electrodes, a current was observed from a faradic process at…
Molecular dynamics (MD) simulations of water confined in nanospaces between layers of talc (system composition Mg(3)Si(4)O(10)(OH)(2) + 2H(2)O) at 300 K and pressures of approximately 0.45 GPa show the presence of a novel 2-D ice structure, and the simulation results at lower pressures provide insight into the mechani…