Materials Literature
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Highly oriented boron carbonitride (BCN) nanostructures consisting of nanotubes and nanofibers have been synthesized by bias-assisted hot-filament chemical vapor deposition from the source gases of B2H6, CH4, N2, and H2. It is found that the B concentration of the BCN nanostructures increases with increasing B2H6 in t…
The following features of multiwalled BN nanotubes were discovered using a field emission high-resolution analytical transmission electron microscope: (i) coexistence of hexagonal and rhombohedral stacking in nanotube shell assembly; (ii) flattening of nanotube cross section, which makes possible clear atomic resoluti…
Adsorption and desorption of an oxygen molecule on carbon nanotubes are investigated using density functional calculations. Several precursor states exist at the edge of armchair nanotubes, whereas an exothermic adsorption takes place at the edge of zigzag nanotubes. We also estimate desorption barriers of a CO molecu…
Surfaces of reactively evaporated In2O3 films were investigated in situ by synchrotron-excited photoemission. Work function, valence band maximum, and electronic states in the band gap were determined as a function of oxygen pressure. Surface and bulk electronic properties can only be explained consistently with the a…
Two methods are proposed to evaluate the second-order elastic constants of quantum mechanically treated solids. One method is based on path-integral simulations in the (NVT) ensemble using an estimator for elastic constants. The other method is based on simulations in the (NpT) ensemble exploiting the relationship bet…
We propose a junction of metal and rare-earth compound semiconductor as the basis for a possible efficient low-temperature thermoelectric device. If an overlayer of rare earth atoms differing from the bulk is placed at the interface, very high values of the figure of merit ZT can be reached at low temperature. This is…
The exciton decay rate at a rough interface in type-II semiconductor superlattices is investigated. It is shown that the possibility of recombination of indirect excitons at a plane interface essentially affects kinetics of the exciton photoluminescence at a rough interface. This happens because of strong correlation…
The excited triplet state deactivation of zinc(II) meso -diaryloctaalkylporphyrins (ZnDAOAP) has been studied over a wide temperature range using transient triplet−triplet absorption spectroscopy together with steady-state and time-resolved phosphorescence techniques. The results from transient absorption measurements…
Our prior designs for molecular-based information storage devices have employed multiple redox-active units organized in weakly coupled, covalently linked arrays. To explore a simpler design, we report here the synthesis of porphyrin arrays where porphyrins with identical oxidation potentials are directly linked to on…
We present the rational design and synthesis of multiporphyrin arrays containing thiol-derivatized linkers for the purpose of multibit molecular information storage. Porphyrin dimers and trimers were synthesized by the Pd-mediated coupling of iodo-substituted and ethynyl-substituted porphyrin building blocks in 5-51%…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTTriplet Energy Transfer in Porphyrin Dimers: Comparison between π- and σ-Chromophore Bridged SystemsJoakim Andréasson, Johan Kajanus, Jerker Mårtensson, and Bo AlbinssonView Author Information Departments of Physical Chemistry and Organic Chemistry Chalmers University…
The structure and orientation of heptylxanthate adsorbed on a ZnS surface have been studied by the FTIR-ATR technique. By using polarized light and the dichroic ratio, we found the average tilt angle to be approximately 44 degrees. The adsorbed layer studied was prepared by self-assembly from solution or by spraying t…
The structure of Pd interacted with acid sites of ZSM-5 was studied by using extended X-ray absorption fine structure (EXAFS). Dispersed PdO was generated on ZSM-5 upon the oxidation treatment, where the degree of dispersion was dependent on the acid amount of ZSM-5 support. The reduction of the dispersed PdO with H 2…
The storage of multiple bits of information at the molecular level requires molecules with a large number of distinct oxidation states. Lanthanide triple-decker sandwich molecules employing porphyrins and phthalocyanines afford four cationic states and are very attractive for molecular information storage applications…
Transparent nanocomposite gels have been synthesized by the sol−gel method using hybrid precursors composed of two triethoxysilane groups and a mid polyether chain [poly(ethylene oxide) or poly(propylene oxide)] of various chain lengths. The end silicate groups are linked with the polyether chain through urea bridges…
The giant, nanoporous Keplerate (NH4)42[Mo132O372(CH3COO)30(H2O)72] was incorporated into a permeable ultrathin film using a stepwise self-assembly strategy. Alternating adsorption of the Keplerate anions and PAH results in single layers with an apparent surface coverage of ≈50%. Such permeable composite coatings may…
Detailed EXAFS (extended X-ray absorption fine structure spectroscopy) measurements have been collected for two nanocrystalline forms of zirconia, namely, dense films of yttria-stabilized cubic zirconia (YSZ) and tetragonal phase powders of pure ZrO 2 . Zr and Y K edge EXAFS spectra for the YSZ films with grain sizes…
Attempts were made to prepare completely regioregular poly(3-dodecylthienylenevinylene) (PDDTV) and the completely regiorandom PDDTV. However, attempts to prepare the regioregular PDDTV by a Heck polymerization of 2-bromo-3-dodecyl-5-vinylthiophene leads to a regioirregular PDDTV that also contains cross-conjugated de…
Glycidol as latent branching AB 2 monomer was used in combination with glycidyl ethers as linear AB comonomers for the preparation of hyperbranched random copolymers with controlled degree of polymerization ( DP n = 42−72) and relatively low polydispersity ( M w /M n < 1.7). Extending previous theoretical consideratio…
The elastic-like and viscous-like viscosity components of model, Brownian hard sphere suspensions were determined. The elastic-like component, sometimes called the thermodynamic component, is due to Brownian motion while the viscous-like component, sometimes called the hydrodynamic component, is due to hydrodynamic in…