Materials Literature
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Gas bubbles are the most potent naturally-occurring entities that influence the acoustic environment in liquids. Upon entrainment under breaking waves, waterfalls, or rainfall over water, each bubble undergoes small amplitude decaying pulsations with a natural frequency that varies approximately inversely with the bub…
A high-nitrogen compound, 3,6-di(azido)-1,2,4,5-tetrazine, was used as precursor for the preparation of carbon nanospheres (see SEM picture) and nitrogen-rich carbon nitrides. The conversions into both carbon-based materials are simple, occur under mild conditions (low temperature, no applied pressure), and require no…
Trace concentrations of polycyclic aromatic hydrocarbons (PAHs) have been successfully detected using surface-enhanced Raman scattering (SERS) spectroscopy. For such purpose, new SERS substrates have been developed, consisting of Ag nanoparticles, either in suspension or immobilized on glass, obtained by a new method…
Extraction processes of natural fibers can be performed by different procedures that include mechanical, chemical and biological methods. Each method presents different advantages or drawbacks according to the amount of fiber produced or the quality and properties of fiber bundles obtained. In this study, biological n…
We analyze the lineshape of x-ray diffraction profiles of GaN epitaxial layers with large densities of randomly distributed threading dislocations. The peaks are Gaussian only in the central, most intense part of the peak, while the tails obey a power law. The $q^{-3}$ decay typical for random dislocations is observed…
X-ray absorption near-edge spectroscopy (XANES) is used to study the N environment in bulk GaN and in GaN{y}As{1-y} epilayers on GaAs (001), for y \~5%. Density-functional optimized structures were used to predict XANES via multiple-scattering theory. We obtain striking agreement for pure GaN. An alloy model with nitr…
In control! Ag2S nanocrystals of predictable size and shape were synthesized from the precursor Ag(SCOPh) in the presence of an amine. Careful tuning of several parameters, such as the reaction temperature and the ratio of amine to precursor, led to Ag2S nanocrystals of varying morphology (red: nanocubes; blue: facete…
The thermal conductivity of the magnetically frustrated, ferroelectric YMnO3 exhibits an isotropic suppression in the cooperative paramagnetic state, followed by a sudden increase upon magnetic ordering. This unprecedented behavior without an associated static structural distortion probably originates from the strong…
Neutron scattering experiments were performed on the undoped and hole-doped Ca$_{2+x}$Y$_{2-x}$Cu$_5$O$_{10}$, which consists of ferromagnetic edge-sharing CuO$_2$ chains. It was previously reported that in the undoped Ca$_2$Y$_2$Cu$_5$O$_{10}$ there is an anomalous broadening of spin-wave excitations along the chain,…
Abstract We study the structural and electronic properties of isolated single‐wall carbon nanotubes (SWNTs) under hydrostatic pressure using a combination of theoretical techniques: Continuum elasticity models, classical molecular dynamics simulations, tight‐binding electronic structure methods, and first‐principles t…
In this paper, we report a simple melt impregnation method by using cheap mesophase pitches (MPs) as carbon precursors to prepare ordered mesoporous carbon with ordered graphitized pore walls at low temperature. This facile procedure includes melting MPs at 140 °C and impregnation of the melt into hexagonal or biconti…
We introduce a lattice model of dimers with directional interactions as a paradigm of molecular fluids or strongly correlated Cooper pairs in electronic systems. The model supports an intermediate phase that is common to both systems. There are two different ideal glasses having no moblity since they possess zero entr…
According to the spin-torque model, current-driven magnetic dynamics in ferromagnetic multilayers is determined by the transfer of electron spin perpendicular to the layers' magnetizations. By separating the largest contributions to the magnetic dynamics, we demonstrate that the dominant effect of spin-torque is rathe…
Arbitrary waves incident on a solid embedded nanoparticle are studied. The acoustic vibrational frequencies are shown to correspond to the poles of the scattering cross section in the complex frequency plane. The location of the poles is unchanged even if the incident wave is nonplanar. A second approach approximating…
The size effects on the optical properties of vanadium dioxide nanoparticles in ordered arrays have been studied. Contrary to previous VO2 studies, we observe that the optical contrast between the semiconducting and metallic phases is dramatically enhanced in the visible region, presenting size-dependent optical reson…
The best of both worlds: The synthesis of carbon-encapsulated iron-based magnetic nanoparticles is described (see picture: left TEM image, right model). With such small catalysts that have macroscopic magnetic properties, the advantages of homogeneous or colloidal and heterogeneous catalysts can be combined.
Uniform nanofibers composed of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] and its blends with poly(3-hexylthiophene) are formed by co-electrospinning their solutions with poly(vinyl pyrrolidone) (PVP) through a coaxial capillary system, followed by extraction of the PVP phase (see Figure). Compared with…
A polymer-stabilized liquid-crystal blue phase with a Kerr constant 170 times larger than that of nitrobenzene is shown to be capable of microsecond electro-optical switching over a wide temperature range in flat Kerr cells, without need for additional surface processing to generate alignment. The Figure shows a polar…
Finding the right angle: The contact angle of nanoparticles at the water/oil interface can be engineered close to 90° by capping with ligands containing carboxylic ester terminal groups. This drives the nanoparticles to self-assemble into close-packed films (see picture), and thus provides the opportunity to create tw…
We report on NMR evidence about a novel effect in La 1 − x Ca x MnO 3 + δ systems with cation deficience. We show that in the low–Ca-doping regime, these systems exhibit a very strong hyperfine field at certain La nuclear sites, which is not present in the stoichiometric compounds. Comparison of our NMR results with r…