Materials Literature
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The ever-increasing industrial demand for nylon-6 (polycaprolactam) necessitates the development of environmentally benign methods of producing its precursor, ε-caprolactam, from cyclohexanone. It is currently manufactured in two popular double-step processes, each of which uses highly aggressive reagents, and each ge…
Cylindrical and pentagonal Ag nanowires (see Figure) are selectively prepared in amorphous carbonaceous sheaths via a controlled hydrothermal reaction. Results indicate that the amorphous coating layer is responsible for the cross-section symmetry selected synthesis. The distinctive optical properties measured fit wel…
We present a comprehensive study of the reversal process of perpendicular magnetization in thin layers of the ferromagnetic semiconductor Ga1−xMnxAs. For this investigation we have purposely chosen Ga1−xMnxAs with a low Mn concentration (x≈0.02), since in such specimens contributions of cubic and uniaxial anisotropy p…
Peptide-amphiphile nanofibers are prepared that incorporate a peptide sequence permitting enzyme-mediated degradation (see Figure). Cleavage of the peptide sequence results in breakdown of the nanostructure and, consequently, the mechanical properties. This novel elastic nanofiber network is able to encapsulate dental…
Electrospinning of polymer nanofibers often begins with a single, straight, elongating, and electrified fluid jet that emanates from a droplet tip when the electric field at the surface is high enough. After some distance an electrically driven bending instability of the elongating jet occurs. For a polymer solution s…
The radial-breathing-like phonon modes (RBLMs) of the double-walled carbon nanotubes are studied in a simple analytical model, in which the interaction force constants (FCs) can be obtained analytically from the continuous model. The RBLMs frequencies are obtained by solving the dynamical matrix, and their relationshi…
We find using LSDA+U band structure calculations that the novel one-dimensional cobaltate Ca$_3$Co$_2$O$_6$ is not a ferromagnetic half-metal but a Mott insulator. Both the octahedral and the trigonal Co ions are formally trivalent, with the octahedral being in the low-spin and the trigonal in the high-spin state. The…
We present density-functional calculations for the interaction energy of monosubstituted benzene dimers. Our approach utilizes a recently developed fully nonlocal correlation energy functional, which has been applied to the pure benzene dimer and several other systems with promising results. The interaction energy as…
The nucleation and growth of single wall carbon nanotubes from a carbon-saturated catalytic particle surrounded by a single sheet of graphene is described qualitatively by using a very restricted number of elementary processes, namely Stone-Wales defects and carbon bi-interstitials. Energies of the different configura…
Phonon spectroscopy is used to investigate the mechanism of current-induced spin torques in nonmagnetic/ferromagnetic (N/F) point contacts. Magnetization excitations observed in the magneto-conductance of the point contacts are pronounced for diffusive and thermal contacts, where the electrons experience significant s…
Near-infrared broadband emission from bismuth-tantalum-codoped germanium oxide glasses was observed at room temperature when the glasses were pumped by an 808 nm laser diode. The emission band covered the O, E, S, C, and L bands (1260-1625 nm), with a maximum peak at approximately 1310 nm, a FWHM broader than 400 nm,…
Films of a symmetric A–B diblock copolymer and A-coated Au nanoparticles cast from a selective solvent for A develop a lamellar surface layer. The surface layers have a low volume fraction of nanoparticles in the A lamellae atop a substrate layer of B cylinders/spheres in an A matrix containing a larger volume fractio…
Mother-of-pearl has a three-level nanoscopic-to-macroscopic hierarchical architecture, which provides storage for organic molecules at the nanoscale. A material that mimics the hierarchical architecture and nanostorage properties of nacre emerges from the simple crystallization of potassium sulfate and poly(acrylic ac…
We report a novel Au-Ag alloy catalyst supported on mesoporous aluminosilicate Au-Ag@MCM prepared by a one-pot synthesis procedure, which is very active for low-temperature CO oxidation. The activity was highly dependent on the hydrogen pretreatment conditions. Reduction at 550-650 degrees C led to high activity at ro…
Theoretical studies on the optical properties of gold triangular prisms in solution are presented to determine how structural modifications affect the extinction spectrum. Well-defined trends in the particle extinction are found to depend on the triangular edge length and the prism thickness. Calculations performed on…
We study the dependence of the thermal conductivity of single-walled nanotubes on chirality, isotope impurity, tube length, and temperature by nonequilibrium molecular-dynamics method with accurate potentials. It is found that, contrary to electronic conductivity, the thermal conductivity is insensitive to the chirali…
Molecular dynamics simulations of nanocrystalline copper under shock loading show an unexpected ultrahigh strength behind the shock front, with values up to twice those at low pressure. Partial and perfect dislocations, twinning, and debris from dislocation interactions are found behind the shock front. Results are in…
Unique single-crystalline octahedral Cu2O nanocages (see Figure) are synthesized in solution by the catalytic reduction of copper tartrate complex into octahedral Cu2O nanocrystals and a subsequent spontaneous hollowing process. A wealth of colorful nanostructures with widely tunable bandgaps in the range 2.6–2.2 eV a…
The thermoelectric power of polycrystalline PbTe samples containing nanometer-sized precipitates of Pb metal is enhanced over that of bulk PbTe. Samples of PbTe containing excess Pb and Ag were prepared using conventional metallurgical heat treatments. These samples are shown, by x-ray diffraction, by microscopy, and…
Short chains and complex networks of interconnected Au nanoparticle chains (see Figure) are produced by a simple template-free approach. Optical spectroscopy and computer simulations show that surface plasmons from individual non-contacting nanoparticles are strongly coupled in the resulting 1D superstructures. These…