Materials Literature
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Low-density polyethylene (LDPE) filled with a small amount of titanium dioxide proves to be very suitable for studying the molecular motion of polyethylene by means of dielectric spectroscopy. The titanium dioxide acts as an oxidizing agent that introduces a small concentration of polar carbonyl groups, which does not…
The design, synthesis, and structural and magnetic properties of the two new bimetallic complexes [Sm(DMF)(4)(H(2)O)(2)Cr(CN)(6)].H(2)O and [Sm(DMF)(2)(H(2)O)(3)Cr(CN)(6)].H(2)O (DMF = N,N-dimethylformamide) are presented. [Sm(DMF)(4)(H(2)O)(2)Cr(CN)(6)].H(2)O was prepared by the reaction between Sm(3+) and [Cr(CN)(6)…
A new process is described for the preparation of chitosan gel beads using molybdate as the gelling agent. This new gelation technique leads to a structure different from that produced during alkaline coagulation of a chitosan solution. Instead of a morphology characterized by large open pores, gel beads produced in a…
We report the hydrothermal synthesis of 10 μm × 100 μm × 10 μm single crystals of the microporous titanosilicate sodium-ETS-4. The crystallization of large needle-shaped Na-ETS-4 crystals is preceded by the formation and subsequent dissolution of the titanosilicate GTS-1. Large Na-ETS-4 crystals are obtained with puri…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTOptimization of the Relaxivity of MRI Contrast Agents: Effect of Poly(ethylene glycol) Chains on the Water-Exchange Rates of GdIII ComplexesDan M. J. Doble, Mauro Botta, Jay Wang, Silvio Aime, Alessandro Barge, and Kenneth N. RaymondView Author Information Department o…
Ab initio density-functional (DFT) investigations of the O−H stretching frequencies are performed on the kaolinite structure. Four distinct OH groups form weak hydrogen bonds with O−H···O distances between 1.8 and 2.6 Å. The O−H stretching frequencies, calculated as the Fourier transforms of the velocity autocorrelati…
We investigate the flow properties of a 2D foam (a confined monolayer of jammed bubbles) submitted to a continuous shear in a Couette geometry. A strong localization of the flow at the moving inner wall is evidenced. Moreover, velocity fluctuations measurements reveal self-similar dynamical structures consisting of cl…
The Si(111)7x7 surface was observed by reflection electron microscopy (REM) and scanning tunneling microscopy (STM) simultaneously in an ultra-high vacuum electron microscope. The distance between the STM tip and the Si surface was detected from the REM image, which showed the real and the mirror image of the tip. We…
Structural and textural studies of a CuO/TiO 2 system modified by cerium oxide were conducted using Raman spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and N 2 absorption (BET specific surface area). The introduction of a minor amount of CeO 2 (Ce 0.09 Ti 0.82 O 1.91 Cu…
The compound NiCo2O4, with spinel-related structure, has been prepared by thermal decomposition of metal nitrates and its bulk structural properties examined by means of magnetic measurements, neutron diffraction, X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). The re…
Single-walled nanotubes (SWNTs) produced by plasma laser vaporization (PLV) and containing oxidized surface functional groups have been studied for the first time with NEXAFS. Comparisons are made to SWNTs made by catalytic synthesis over Fe particles in high-pressure CO, called HiPco material. The results indicate th…
A generic statistical mechanical model is presented for the self-assembly of chiral rod-like units, such as beta-sheet-forming peptides, into helical tapes, which with increasing concentration associate into twisted ribbons (double tapes), fibrils (twisted stacks of ribbons), and fibers (entwined fibrils). The finite…
The absorption and extinction spectra of Ge nanocrystals in silica formed by ion implantation are studied using photothermal deflection and transmission spectroscopies. It is found that scattering makes a significant contribution to the extinction spectrum, damping the spectral features and resulting in a Rayleigh sca…
X-ray absorption near edge structure (XANES) spectra of hard amorphous a-Si–C–N thin films with various compositions were measured at the C and N K-edge using sample drain current and fluorescent modes. The C K-edge XANES spectra of a-Si–C–N contain a relatively large 1s→π* peak, indicating that a substantial percenta…
The influence of confinement on the freezing transition of hard spheres is investigated. Two limiting cases are considered: (1) large systems, where walls weakly perturb the bulk system, and (2) small systems where the influence of geometry becomes important. In the first situation, the shift in coexisting densities i…
Measurements with 26 fs pulses that cover the Q(0–0) band of silicon 2,3-naphthalocyanine bis(trihexylsilyloxide) yielded an initial anisotropy of 0.40 that decayed to 0.12 over 200 fs. This contradicts theories predicting anisotropy decay from 7/10 to 1/10. Including ground state bleaching and excited state absorptio…
Electronic transport properties of the stable binary Cd5.7Yb quasicrystal and a quasicrystal in the Y–Mg–Zn family is presented. Electrical conductivity in these systems is an order of magnitude higher than other quasicrystals, resulting in larger thermal conductivity values due to enhanced electronic contributions (λ…
Structural and transport properties of individual micron-sized graphitic disks with less than one hundred graphene layers are measured. Mesoscopic devices of any arbitrary geometry can be fabricated at the center of such disks by focussed ion beam lithography, with the rest of the disk serving as low-resistance contac…
Closed end (10, 10) single walled carbon nanotubes (SWNTs) have been opened by oxidation at their ends and at wall defect sites, using ozone. Oxidation with ozone, followed by heating to 973 K to liberate CO and CO2, causes etching of the nanotube surface at carbon atom vacancy defect sites. The rate of adsorption of…
We present studies of the ultrafast dynamics of photoexcited carriers in thin-film nanocrystalline silicon materials in which the degree of crystallinity has been systematically varied by controlling the deposition conditions. Femtosecond pump-probe measurements reveal a multicomponent response that can be understood…