A TiP2O7 superstructure

A room-temperature structural model of titanium pyrophos­phate, TiP₂O₇, has been determined from synchrotron X-ray data. The structure consists of TiO₆ octahedra and PO₄ tetrahedra sharing corners in a three-dimensional network. The PO₄ tetrahedra form P₂O₇ groups connecting the TiO₆ octahedra. The 3 × 3 × 3 superstructure differs substantially from the parent AB₂O₇ structure. The P—O—P bonding angles of the pyrophosphate group are between 141.21 (12) and 144.51 (13)° for those groups not located on the threefold axis. The individual TiO₆ octahedra and PO₄ tetrahedra are somewhat distorted.     

Resonant Auger decay study of core-excited OCS

The present work aims at characterizing short-lived C1s⁽⁻¹⁾π^*(1) core-excited states of the OCS molecule based on the analysis of the vibrational fine structure and lineshape profiles of the high-resolution resonant Auger decay spectra recorded at the excitation energies along the C1s→π^* resonance in the binding energy region 15–19 eV. Very different behavior in terms of lineshape and resonant enhancement is observed for the , and final states. This is explained by (1) the variation in the C–O bond lengths for the states involved in the electronic relaxation and (2) different contributions in terms of Mulliken population to the molecular orbitals determining the electronic character of the corresponding states. Since the final-state geometries are known from a number of previous experiments and ab initio calculations, the geometry of the C1s⁽⁻¹⁾π^*(1) intermediate states can be predicted in analogy with e.g. the N₂, CO₂ and N₂O molecules.     

Possible role of charge transport in enhanced carbon nanotube growth

We consider the role of electric fields during metal-catalysed thermal chemical vapour deposition growth of carbon nanotubes and show that enhanced growth occurs from a negatively biased electrode. An electric field, applied externally to the growing tubes and/or generated as a result of electron emission or self-biasing, may strongly affect the carbon supply through the catalyst nanoparticle, enhancing the growth rate. Different aspects of the growth process are analysed: the nature of the nanoparticle catalysis, carbon dissolution kinetics, electron emission from the nanotube tips, charge transport in the nanotube–catalytic nanoparticle system and carbon drift and diffusion through the catalyst under the action of the electric field. A fundamental tenet for modelling of charge-transport dynamics during the nanotube growth process is proposed. PACS 81.07.De; 81.15.Gh     

Electric field aligned growth of single-walled carbon nanotubes

Electric field aligned, single-walled carbon nanotubes are grown between electrodes using thermal chemical vapour deposition (CVD) of methane. The growth occurs on a thin film layered catalyst of aluminium, iron and molybdenum patterned on top of electrodes. The nanotubes bridge 10 μm sized electrode gaps and have a typical diameter of less than 2 nm as measured by Raman spectroscopy and atomic force microscopy. We present electrical transport measurements on a directly grown nanotube which shows p-type semiconducting behaviour.     

The directing effect of annelated rings in aromatic systems—XI : Bromination of bicyclic phenols with heterocyclic annelated rings

Bicyclic phenols of type 1 with annelated rings containing a N or an O heteroatom (X = N or O) as well as the ring opened analogs have been brominated and the product distribution determined. The results indicate that while most annelated rings have a directing effect to the ar-β position of the molecule, a 6-membered annelated ring is an exception and it facilitates substitution in the ar-α position.