Materials Literature
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The photochromic pair 1,1‘-binaphthylpyran ( 1 ) and 2-hydroxy-2‘-hydroxymethyl-[1,1‘]-binaphthylene ( 2 ) was examined to assess suitability as optical triggers in a liquid crystal switch. Both 1 and 2 are chiral and they were resolved into enantiomers by HPLC. The absorption and circular dichroism spectra of optical…
To identify structural features important for low temperature activity in archaeal proteins, elongation factor 2 (EF-2) genes (aef2) were sequenced from psychrophilic, mesophilic and thermophilic methanogens. Scatter plots were used to compare evolutionary distances for EF-2 amino acid sequences vs. 16S-rRNA sequences…
The morphology and self-diffusion in thin films of asymmetric polystyrene- b -2-vinylpyridine (PS−PVP) diblock copolymers were investigated by secondary ion mass spectrometry (SIMS). An oscillatory depth profile of the PVP volume fraction is observed, implying a periodic arrangement of layers of PVP spherical domains…
1 H and 13 C nuclear magnetic resonance (NMR) relaxation studies of thiophenol-capped CdS nanocrystals are presented. The transverse and longitudinal relaxation times were investigated as a function of nanocrystal radius, and the transverse relaxation time was also studied as a function of temperature. Both proton and…
Copper(II)-mediated oxidative coupling of the blue, 18-electron mononuclear complex [Ru II {C 6 H 3 (CH 2 NMe 2 ) 2 -2,6}(terpy)]Cl, 3 (terpy = 2,2‘;6‘,2‘‘-terpyridine), affords the unique diamagnetic, binuclear 34-electron complex [(Ru III ) 2 (4,4‘-{C 6 H 2 (CH 2 NMe 2 ) 2 -2,6} 2 )(terpy) 2 ](CuCl 2 ) 4, 5a . This…
A large number of ternary hydrides of transition metals and alkali or alkaline earth metals have been synthesized and structurally characterized in the last twenty years. These compounds exhibit a puzzling variety of compositions, transition metal coordination numbers, transition metal coordination geometries, and dis…
The effect of inclusion of diarylethenes in cyclodextrin cavities on cyclization quantum yields and on circular dichroism (CD) spectral changes by photoirradiation was studied. The addition of β- and γ-cyclodextrins to an aqueous solution of the open-ring form of 2,2‘-dimethyl-3,3‘-(perfluorocyclopentene-1,2-diyl)bis(…
The electronic and optical properties of (Zn,Mg)(S,Se) wide-gap solid solutions are studied using ab initio techniques and starting from the previously determined atomistic structure of the alloy. Compositional disorder is shown to close substantially the gap with respect to the predictions of the virtual-crystal appr…
Solutions containing KAu(CN) 2 (∼5 × 10 - 4 M), methanol (0.3 M), and nitrous oxide (2.5 × 10 - 2 M) are γ-irradiated in the presence of colloidal gold (∼6 × 10 - 5 M; mean particle size, 15 nm). The hydroxymethyl radicals, • CH 2 OH, which are generated in these solutions, reduce Au(I) in Au(CN) 2 -, and the reduced…
Strong and sustained electron emission at low electric fields was observed in undoped, nanostructured diamond. Electron emission of 10 milliamperes per square centimeter was observed at applied fields of 3 to 5 volts per micrometer. These are the lowest fields ever reported for any field-emitting material at technolog…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSelf-Assembly of [2]Catenanes Containing Metals in Their BackbonesMakoto FujitaView Author Information Coordination Chemistry Laboratories, Institute for Molecular Science, Myodaiji, Okazaki 444, Japan Cite this: Acc. Chem. Res. 1999, 32, 1, 53–61Publication Date (Web):Novem…
The layered and hexagonal yttrium-based surfactant mesophases templated by anionic surfactant (C(n)()H(2)(n)()(+1)OSO(3)(-) and C(n)()H(2)(n)()(+1)SO(3)(-)) assemblies were synthesized by the homogeneous precipitation method using urea. The layered mesophase is formed of a layered but curving or bending microstructure…
The unsymmetrical porphyrazine (tetraazaporphyrin) bearing a single peripheral bis(dimethylamino) functionality, Mg[pz(NMe(2))(2)(Pr)(6)], was prepared by base-catalyzed cross condensation of dipropyl maleonitrile (in excess) with dimethylamino maleonitrile. The freebase (2H[pz(NMe(2))(2)(Pr)(6)]) and centrally metala…
Cannabis plants have been cultivated in Europe, Asia, Africa and the Americas for hundreds, perhaps even thousands of years as a source of three main products-hemp fibre, cannabis seeds and medicinal or narcotic preparations (Fairbairn, 1976). Hemp fibre is obtained from cannabis stems, and has been used over the cent…
The temperature dependence of the 7 Li NMR shift was measured for LiMn 2 O 4, LiMn 2 - y Ni y O 4 ( y = 0.1, 0.25, 0.33), LiMn 2 - y Co y O 4 ( y = 0.25, 0.5, 1.0), Li[Mn 2 - y Li y ]O 4 ( y = 0.1, 0.33), and λ-MnO 2 spinel oxides. The 7 Li NMR shift can be separated into temperature-independent and -dependent compone…
In the search for boron nanotubes, the geometrical duals of carbon nanotubes, we employ the Euler−Poincare formula for a cylinder, P − C + F = 0. As may be seen in the attached figure, boron nanotubes may be imagined as arising from a correspondence between a boron atom and the center of each of the faces in a carbon…
Au colloids in the 2-3-nm size regime were prepared by in situ reduction of HAuCl(4) in the presence of poly(amidoamine) dendrimers. The dendrimers encapsulate the colloids, imparting stability to the aqueous colloidal solutions. The nanocomposite materials can be isolated by precipitation. The dendrimer generation us…
A quantitative analysis of gallium species (GaO 4 tetrahedra and GaO 6 octahedra) by means of X-ray absorption spectroscopy (XANES and EXAFS) at the Ga K-edge was performed on a series of gallium oxides with various phases and SiO 2 -supported ones. XANES spectra of gallium oxides showed two distinguishable peaks that…
On the basis of a new ab initio, all-electron response scheme, formulated within time-dependent density-functional theory, we solve the puzzle posed by the anomalous dispersion of the plasmon linewidth in K. The key damping mechanism is shown to be decay into particle-hole pairs involving empty states of d-symmetry. W…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTNanometer Gold Clusters Protected by Surface-Bound Monolayers of Thiolated Poly(ethylene glycol) Polymer ElectrolyteW. Peter Wuelfing, Stephen M. Gross, Deon T. Miles, and Royce W. MurrayView Author Information Kenan Laboratories of Chemistry University of North Caroli…