Materials Literature
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When incorporated into proteins, fluorinated amino acids have been utilized as 19F NMR probes of protein structure and protein-ligand interactions, and as subtle structural replacements for their parent amino acids which is not possible using the standard 20-amino acid repertoire. Recent investigations have shown the…
Surface-alkoxylated silica can be prepared by reacting precipitated silica with high-boiling and polymeric alcohols. The structure of the products was investigated through 13 C and 29 Si MAS NMR experiments. The influence of the alkoxy group structure and density on the hydrolytic stability of the alkoxylated silicas…
Chlorin building blocks incorporating a geminal dimethyl group in the reduced ring and synthetic handles in specific patterns at the perimeter of the macrocycle are expected to have utility in biomimetic and materials chemistry. A prior route employed condensation of a dihydrodipyrrin (Western half) and a bromodipyrro…
A family of diaminobutane core, poly(propylene imine) dendrimers coordinated to Cu(II), DAB-Am(n)-Cu(II)x (n = 4, 8, 16, 32, 64, x = n/2), was studied by means of extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) spectroscopies. The geometry of the dipropylene triamine (…
An XAS investigation was undertaken to understand the mechanism of our platinum deposition process. This process is based on H 2 PtCl 6 impregnation onto activated carbon followed by current pulses reduction. After each step of the process and during the electrochemical reduction, ex situ and in situ dispersive X-ray…
The effect of initial chain length before cross-linking and sulfur/accelerator amount during curing of natural rubber samples on network parameters (effective chain density, gel fraction, amount of chain ends, entanglement density, trapping factor, and relaxation and correlation times) is investigated by means of prot…
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…