Materials Literature
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Quantum dots are clusters of atoms (or molecules) that are small enough that their electronic states are discrete. They can be prepared with a variety of compositions and covering ligands but are not quite identical. In particular, the dots will have a variable size. The study of the properties of individual dots is a…
Rayleigh scattering spectra and Raman spectra from single bundles of aligned single-wall carbon nanotubes (SWNTs) have been obtained with dark field optical microscopy and Raman microscopy. Rayleigh scattering spectrum reveals resonance peaks due to the optically allowed interband transitions in SWNTs. The intensity o…
Homoassociates of the achiral title porphyrins in acid solutions show spontaneous symmetry breaking, which can be detected by circular dichroism (CD). The CD spectra are due to differential scattering and differential absorption contributions, the relative significance of which is related to the shape and size of the…
Polymeric supports have become a big necessity for automated synthesis and combinatorial chemistry, yet, the loading capacities of most polystyrene resins are very limited (typically < 1.5 mmol x g(-1)). Dendrimers and hyperbranched polymers have been discussed for this application and now became readily available. Th…
Combinatorial catalysis is the systematic preparation, processing, and testing of large diversities of chemically and physically different materials libraries in a high-throughput fashion. It also embodies microfabrication, robotics, automation, instrumentation, computational chemistry, and large-scale information man…
Transition-metal-substituted polyoxometalates (TMSP) of the type [MII(H2O)PW11O39]5- (M = Co, Zn) and [SiW9O37(CoII(H2O))3]10- have been chemically anchored to modified macroporous (400 nm pores), mesoporous (2.8 nm pores), and amorphous silica surfaces. The materials were characterized by solid-state 31P MAS NMR, UV-…
Electron microdiffraction study of phase transition in ${\mathrm{La}}_{2/3}{\mathrm{Ca}}_{1/3}{\mathrm{MnO}}_{3}$ revealed temperature-dependent $(h+1/2,0,l)$ diffraction spots. Their intensity peaks at ${T}_{c}.$ Quantitative electron diffraction intensity analysis shows that they come from nanometer-sized domains wi…
We study, through large scale stochastic simulations using the noise reduction technique, a large number of simple nonequilibrium limited mobility solid-on-solid growth models. We find that d=2+1 dimensional surface growth in several noise reduced models (most notably the Wolf-Villain and the Larger-Curvature model) e…
In the absence of coalescence, coarsening of emulsions (and foams) is controlled by molecular diffusion of dispersed phase between droplets/bubbles. Studies of dilute emulsions have shown how the osmotic pressure of a trapped species within droplets can ``osmotically stabilise'' the emulsion. Webster and Cates (Langmu…
We have performed density functional theory calculations with the generalized gradient approximation to investigate CO oxidation on a close-packed transition metal surface, Pd(111), and a more open surface, Pd(100), aiming to shed light on surface structure effects on reaction pathways and reactivity, an important iss…
Rings of 24 atoms form part of the two-dimensional structure of the novel compounds [NdM(bpym)(H2O)4(CN)6]⋅3 H2O (M = Fe (1), Co (2); bpym = 2,2′-bipyrimidine). These compounds are the first two-dimensional cyano-bridged species containing lanthanide and transition metal centers (see picture). The structures and magne…
Transport of redox-active probe ions through multilayers made from highly charged polyelectrolytes is described. Because of intrinsic charge balance between polyelectrolyte segment ion pairs, there are no sites for the exchange of small ions within the bulk of as-made multilayers. In the presence of salt in the extern…
Largely monodisperse, crystalline nanoscale oxide particles (for example, Cu2O, TiO2, Nb2O5) are preparatively accessible with the polyol method (see picture). The colloidal suspensions of the particles thus obtained can be employed readily for the homogeneous coating of various substrates (for example, glass plates,…
We report a nanoscale "lost-wax" method for forming colloids with size distributions around 5% and their corresponding colloidal crystals. Macroporous polymer templates are first prepared from a silica colloidal crystal. We then use the uniform and interconnected voids of the porous polymer to generate a wide variety…
Dc-magnetization, x-ray diffraction, and Raman-scattering studies in polycrystalline $({\mathrm{La}}_{1\ensuremath{-}y}{\mathrm{Nd}}_{y}{)}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{MnO}}_{3}$ $(y=0.0,0.5,1.0,$ and $x=1/3)$ samples are presented. The samples with $y=0.5$ and 1.0 show complex magnetic states at low t…
Polyurethane networks bearing dendritic wedges of the second, third and fourth generation were prepared by polymerization of dendritic diols of the corresponding generation with a commercially available triisocyanate (Desmodur RFE). The formation of a three-dimensional network was greatly influenced by the shielding e…
We report the synthesis of a new series of cyclophanes 11a-d by ester-forming macrocyclization reactions of diol 9 with the dicarbonyl chloride derivatives of benzene, thiophene, ferrocene, and diphenyl ether, 10a-d, respectively. Compounds 11a-d display a two-electron, quasireversible oxidation wave in the cyclic vol…
The substitution of Ga(3+) into the Jahn--Teller distorted, antiferromagnetic perovskites LaMnO(3) and NdMnO(3) strongly affects both the crystal structures and resulting magnetic ordering. In both compounds the Ga(3+) and Mn(3+) cations are disordered over the six coordinate sites. La(2)GaMnO(6) is a ferromagnetic in…
A series of chlorinated aliphatic compounds (RCI, including carbon tetrachloride (PCM), 1,1,1-trichloroethane (TCA), 1,1,2,2-tetrachloroethane (TeCA), pentachloroethane (PCA), hexachloroethane (HCA), trichloroethene (TCE), tetrachloroethene (PCE), trichloronitromethane (chloropicrin, CP), and trichloroacetonitrile (TC…
Substitution of Mn by Fe in ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{Mn}}_{1\ensuremath{-}y}{\mathrm{Fe}}_{y}{\mathrm{O}}_{3}$ induces a gradual transition from a metallic ferromagnet with a high Curie temperature ${(T}_{c}\ensuremath{\sim}370 \mathrm{K})$ for $y=0,$ to a ferromagnetic insulator with low ${T}_{…