Materials Literature
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As part of a structure-aided effort to design clinically useful inhibitors of metallo-beta-lactamases, the X-ray crystal structure of a complex between the metallo-beta-lactamase from Bacteroides fragilis and 4-morpholinoethanesulfonic acid (MES) has been determined and a model for the structure has been refined to a…
A series of benzyl-substituted phthalonitriles, substituted at the 3-, 4-, and 4,5-positions, underwent varied condensations with phthalonitrile to give a series of protected (monohydroxy- and polyhydroxyphthalocyaninato)zinc(II) derivatives which were readily cleaved to give several hydroxyphthalocyanines (ZnPc) (pht…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTDerivatization of Porous Silicon by Grignard Reagents at Room TemperatureNamyong Y. Kim and Paul E. LaibinisView Author Information Departments of Chemistry and Chemical Engineering Massachusetts Institute of Technology Cambridge, Massachusetts 02139 Cite this: J. Am.…
The crystal structure of syndiotactic polystyrene (sPS) in its stable α form (a so-called “superstructure” named α‘‘) is reevaluated. As shown by all previous investigations, the trigonal unit cell contains three triplets of extended sPS chains. The azimuthal orientation of the three triplets is shown to differ from t…
A series of neutral pyridyl adducts involving the strong Lewis acids BF 3 and B(C 6 F 5 ) 3 has been prepared, and their second-order nonlinear optical coefficients (EFISH method) have been examined. The formation of the pyridyl−boron bond leads to enhancement of the dipole moments and second-order NLO coefficients (β…
The photochemistry of a molecular triad consisting of a porphyrin (P) covalently linked to a carotenoid polyene (C) and a fullerene derivative (C 60 ) has been studied at 20 K by time-resolved EPR spectroscopy following laser excitation. Excitation of the porphyrin moiety yields C− 1 P−C 60, which decays by photoinduc…
The established macroscopic equations of motion for two phase immiscible displacement in porous media are known to be physically incomplete because they do not contain the surface tension and surface areas governing capillary phenomena. Therefore a more general system of macroscopic equations is derived here which inc…
The glass transition temperature ( T g ) of layers of stereoregular poly(methyl methacrylate) (PMMA) spin-cast on silicon and aluminum surfaces has been investigated by ellipsometry. The interfacial specific interactions were highlighted and quantified by infrared reflection absorption spectroscopy. It was found that…
Zirconia-supported tungsten oxide catalysts were prepared by suspending hydrous zirconium oxide in aqueous solutions of ammonium metatungstate at their natural pH. The suspensions were refluxed at 383 K followed by evaporation of the water, drying and calcination. The WO 3 loadings were chosen between 3.6 and 32 wt %…
Several strategies are reported that allow carbon black (CB) particles to be selectively localized at the interface of polyethylene/polystyrene (PE/PS) blends used as models of two-phase polyblends. A first general approach relies upon a kinetic control, i.e., the choice of such processing conditions that the CB parti…
The bias-enhanced nucleation of diamond on Si(100) has been studied by x-ray absorption near-edge spectroscopy (XANES) and atomic force microscopy, two techniques well suited to characterize nanometric crystallites. Diamond nuclei of ∼15 nm are formed after 5 min of bias-enhanced treatment. The number of nuclei and it…
Field emission properties of undoped chemical vapor deposited diamond and diamondlike carbon films have been measured for a variety of different deposition conditions. The nature and appearance of the damage site after testing, together with the mathematical form of the observed current–voltage relations, are correlat…
Thin films of Ag2Te were obtained by vapor transport and electron beam evaporation methods. The film phase and chemical compositions were analyzed by x-ray diffraction and x-ray photoelectron spectroscopy analyses, respectively. Film composition was close to stoichiometric with a slight excess of tellurium. Strong (1̄…
We study the equilibrium phase diagram of binary mixtures of hard spheres as well as of parallel hard cubes. A superior cluster algorithm allows us to establish and to access the demixed phase for both systems and to investigate the subtle interplay between short-range depletion and long-range demixing.
Liquid crystal alignment layers are prepared using a noncontact method based on laser ablation. Nonpolarized light from a KrF excimer laser at 248 nm is exposed through a phase mask to etch gratings of period 1.1 μm onto polyimide alignment layers. Twisted nematic cells were prepared using one rubbed and one grating a…
A library of 256 differently doped thin films of (BaxSr1−x)TiO3 (where 0.5<x<1.0) was generated on a 1 in.×1 in. LaAlO3 substrate using multistep thin-film deposition techniques together with a quaternary masking strategy. Appropriate postannealing processing afforded high-quality epitaxial thin films. T…
We study the theory of the anomalous x-ray scattering in relation to its role as a detector of the orbital orderings and excitations in perovskite manganites. The scattering matrix is given by virtual electron excitations in Mn from the $1s$ level to the unoccupied $4p$ level. We find that the orbital dependence of th…
Low frequency impedance spectroscopy was applied on a Langmuir monolayer of alkylthiol passivated 35 \AA{} diameter silver quantum dots, as a function of interparticle separation distance. As interparticle spacing decreases below 30% of particle diameter, a reduction in interparticle charge tunneling time is observed.…
Optical conductivity spectra of La_{0.7-y}Pr_{y}Ca_{0.3}MnO_3 were systematically investigated. For metallic samples, the spectral weight below 0.5 eV, whose magnitude can be represented by the effective carrier number N_{eff}(0.5 eV), increases as temperature becomes lower. Regardless of the Pr doping, all the measur…
X-ray absorption and photoemission spectra have been used to measure the band edges of silicon nanocrystals with average diameters ranging from 1 to 5 nm. We compare the experimentally measured band edges to recent electronic structure calculations and find that the experimentally measured band gap is smaller than tha…