Self-organized ZnAl2O4 nanostructures grown on -sapphire

Self-organized ZnAl₂O₄ nanostructures with the appearance (in SEM) of high aspect ratio horizontal nanowires are grown on uncatalysed c-sapphire by vapour phase transport. The nanostructures grow as three equivalent crystallographic variants on c-sapphire. Raman and cathodoluminescence spectroscopy confirm that the nanostructures are not ZnO and TEM shows that they are the cubic spinel, zinc aluminate, ZnAl₂O₄, formed by the reaction of Zn and O with the sapphire substrate.     

Molecular Rydberg transitions. Intermediate coupling in simple bromides

An intermediate coupling analysis of the low-energy π → σ Rydberg transitions of hydrogen bromide, cyanogen bromide, acetylene bromide and alkyl bromides is presented. Exchange and spin-orbit coupling parameters are calculated and their variations discussed. The Br 5s orbital is delocalized in the larger alkyl bromides and Br 4p is heavily involved in π bonding in acetylene and cyanogen bromides.     

Electrical characterisation of phosphorus-doped ZnO thin films grown by pulsed laser deposition

Phosphorus-doped ZnO films were grown by pulsed laser deposition using a ZnO:P₂O₅-doped target as the phosphorus source with the aim of producing p-type ZnO material. ZnO:P layers (with phosphorus concentrations of between 0.01 to 1 wt%) were grown on a pure ZnO buffer layer. The electrical properties of the films were characterised from temperature dependent Hall-effect measurements. The samples typically showed weak n-type conduction in the dark, with a resistivity of 70 Ω cm, a Hall mobility of μ_n0.5 cm² V ⁻¹ s⁻¹ and a carrier concentration of n3×10¹⁷ cm⁻³ at room temperature. After exposure to an incandescent light source, the samples underwent a change in conduction from n- to p-type, with an increase in mobility and decrease in concentration for temperatures below 300 K.     

Nucleophilic Reactivity of a Copper(II)–Superoxide Complex

Metal‐bound superoxide intermediates are often implicated as electrophilic oxidants in dioxygen‐activating metalloenzymes. In the nonheme iron α‐ketoglutarate dependent oxygenases and pterin‐dependent hydroxylases, however, Fe^III–superoxide intermediates are postulated to react by nucleophilic attack on electrophilic carbon atoms. By reacting a Cu^II–superoxide complex ( 1 ) with acyl chloride substrates, we have found that a metal–superoxide complex can be a very reactive nucleophile. Furthermore, 1 was found to be an efficient nucleophilic deformylating reagent, capable of Baeyer–Villiger oxidation of a number of aldehyde substrates. The observed nucleophilic chemistry represents a new domain for metal–superoxide reactivity. Our observations provide support for the postulated role of metal–superoxide intermediates in nonheme iron α‐ketoglutarate dependent and pterin‐dependent enzymes.