Materials Literature
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The Raman scattering spectra of Ba 3 MoNbO 8.5 and Ba 7 Nb 4 MoO 20, two cation-deficient perovskite-like oxides, are presented for the first time and analyzed in an attempt to confirm the distribution of octahedra and tetrahedra proposed in recent structural investigations. The Raman spectra are discussed in relation…
Bis(N-ethylideneethanamine)ruthenium(ii) porphyrins, [Ru11(Por)(N(Et)=CHMe)2] (Por=TTP, 4-Cl-TPP), were prepared by the reaction of dioxoruthenium(VI) porphyrins with triethylamine in approximately 85% yields. The reaction between dioxoruthenium(VI) porphyrins and benzophenone imine afforded bis(diphenylmethyleneamido…
Unusual thermal robustness is exhibited by a homoleptic ytterbium complex, which sublimes intact at temperatures in excess of 500 °C/760 Torr. Employment of a (N)-nPr substituted ketoiminate ligand provides notable metal encapsulation and ensures substantial air stability and vapor-phase integrity. The octahedral coor…
A new series of homo- and heterometallic oxalato-bridged dinuclear compounds of formulas [Et4N]4[MM'(ox)(NCS)8] ([Et4N]+ = [(C2H5)4N]+; ox = C2O4(2-)) with MM' = Cr(III)-Cr(III) (1), Fe(III)-Fe(III) (2), and Cr(III)-Fe(III) (3) is reported. They have been structurally characterized by infrared spectra and single-cryst…
The design, synthesis, and solution properties of six constitutional isomers of dendrimer-like star polymers is described. Each of the polymers have comparable molecular weights (∼80 000), narrow polydispersities (<1.19) and an identical number of branching junctures (45) and surface hydroxyl functionalities (48). The…
Three C 2 -symmetric (10 R,11 R )-diethyl substituted dibenzosuberane (DBS)-based helicenes with varying steric and conjugation demands of their bottom fragments were synthesized. The X-ray analyses of their precursors-episulfides reveal the preferred conformation of the DBS skeleton possessing equatorially oriented e…
When the dimensions of matter are reduced to the nanometer scale and beyond, strange properties often emerge. In their Perspective, Tosatti and Prestipino discuss the weird gold nanowire structures reported by Kondo and Takayanagi. They explain why the wires may be helical and only form certain "magic" sizes. Other me…
The reorientation dynamics of local tangent vectors of chains in isotropic amorphous melts containing semiflexible model polymers was studied by molecular dynamics simulations. The reorientation is strongly influenced both by the local chain stiffness and by the overall chain length. It takes place by two different su…
The spray pyrolysis technique has been employed to prepare uniform, large-area thin-film coatings of PbS on glass and on fluorine-doped tin oxide (FTO) conducting substrates at various substrate temperatures. Growth of polycrystalline PbS films occurred at a lower temperature ( T S = 275 °C) on conducting substrate th…
For future nanomechanical devices to be realized, sophisticated ways of manipulating small structures must be developed, and fundamental elements of macroscopic machines, such as switches and bearings, must be reproduced in the nanoscale. Forró highlights the nanotube nanobearings and nanoswitches reported by Cumings…
Mesoporous silica materials with well-ordered hexagonal structure were synthesized under acidic conditions by using various acid sources HX. The induction time for the formation of mesostructural precipitation increases in the lyotropic series HNO 3 < HBr < HCl < H 2 SO 4 under the same acid concentration. The inducti…
Photoinduced orientational behavior of polymethacrylates with side chains (amorphous polymers, pMAz2 and C2MeO, and liquid crystalline polymers, C6MeO and C12MeO) with different alkylene spacer lengths ( n = 2, 6, 12) were investigated by means of polarized Fourier transform infrared (FT-IR) and UV−vis absorption spec…
Aluminosilicate MCM-41 materials with Si/Al ratio between 10 and 50 were prepared via direct mixed-gel synthesis, and their hydrothermal stability in boiling water was investigated using a variety of techniques including powder XRD, N 2 sorption studies, and elemental analysis. The incorporation of Al markedly improve…
A highly concentrated (17 vol.%) Fe-C nano-particle system, with a narrow size distribution $d = 5.4\pm 0.4$ nm, has been investigated using magnetic ac susceptibility measurements covering a wide range of frequencies (17 mHz - 170 Hz). A dynamic scaling analysis gives evidence for a phase transition to a low temperat…
A simulated annealing algorithm is employed to generate a stochastic model for a Berea and a Fontainebleau sandstone with prescribed two-point probability function, lineal path function, and ``pore size'' distribution function, respectively. We find that the temperature decrease of the annealing has to be rather quick…
The Tm-Ba-Cu-O solder can be successfully used to produce a superconductive joint between MT-YBCO parts. The peculiarities of solidification, phase formation, structure transformations and electromagnetic properties of MT-YBCO soldered with TmBa2Cu3O7-d are discussed.
Silicotitanates are nanoporous materials that have been used as selective ion exchangers for removing cesium from waste streams and catalysts for promoting oxidation and hydroxylation reactions. The local bonding configurations and network charge distribution are known to influence the selectivity and reactivity of th…
The first neutral pentaatomic tetracoordinate planar carbon molecules, CAl 3 Si and CAl 3 Ge, as well as their anions, CAl 3 Si - and CAl 3 Ge -, were experimentally observed in the gas-phase and characterized by ab initio calculations and anion photoelectron spectroscopy. A four-center bond involving ligand−ligand in…
Suspended gold nanowires were made in an ultra-high vacuum. The finest of them was 0.6 nanometer in diameter and 6 nanometers in length. By high-resolution electron microscopy, they were shown to have a multi-shell structure composed of coaxial tubes. Each tube consists of helical atom rows coiled round the wire axis.…
Nearly full color emission has been achieved using quantum dot (QD)–polymer composites. The fluorescence of the resulting composites spans the entire visible range with narrow emission profiles and high photoluminescence (PL) quantum yields. Moreover, mixed colors are easily produced by controlling the mixing ratio of…