Synthesis and Characterization of ZnO Nanowires

Zinc oxide is a wide bandgap (3.37 eV) semiconductor with a hexagonal wurtzite crystal structure. ZnO prepared in nanowire form may be used as a nanosized ultraviolet light-emitting source. In this study, ZnO nanowires were prepared by vapor-phase transport of Zn vapor onto gold-coated silicon substrates in a tube furnace heated to 900 ?C. Gold serves as a catalyst to capture Zn vapor during nanowire growth. Size control of ZnO nanowires has been achieved by varying the gold film thickness…     

Dichlorodinickel(I) Complexes with μ2-CO or μ2-CS Bridges and Trimethylphosphane Ligands: Homologous Composition,but Different Frameworks

High ligand mobility is shown by the coordinatively unsaturated nickel(I ) compound 1 with a short Ni–Ni distance and an asymmetric CO bridge. The thio homologue 2 contains the novel (thiocarbonyl)trimethylphosphorane bridging ligand, which sits like a “stork's nest” on top of the roof-shaped dinuclear complex. In contrast to 1 , complex 2 does not show fluctional behavior and can be methylated without decomposition. X=Cl, Me.     

Transition metals in silicon

A review is given on the diffusion, solubility and electrical activity of 3d transition metals in silicon. Transition elements (especially, Cr, Mn, Fe, Co, Ni, and Cu) diffuse interstitially and stay in the interstitial site in thermal equilibrium at the diffusion temperature. The parameters of the liquidus curves are identical for the Si:Ti — Si:Ni melts, indicating comparable silicon-metal interaction for all these elements. Only Cr, Mn, and Fe could be identified in undisturbed interstitial sites after quenching, the others precipitated or formed complexes. The 3d elements can be divided into two groups according to the respective enthalpy of formation of the solid solution. The distinction can arise from different charge states of these impurities at the diffusion temperature. For the interstitial 3d atoms remaining after quenching, reliable energy levels are established from the literature and compared with recent calculations.     

Kalorimetrische Untersuchungen des Wassereinflusses auf den Lösungsvorgang von Aerosol OT in apolaren Lösungsmitteln

Calorimetric Investigations of the Effect of Water on the Solution Process of Aerosol OT in Apolar Media. Heats of solution of Aerosol OT in apolar solvents are influenced considerably by already small amounts of water. Calorimetric investigations of the solution process with differently dried surfactant and solvent samples showed the predominating effect on the heats of hydration with regard to the ionic and polar groups of the surfactant. Only if the hydration is finished prior to the process of solution, the latter is endothermic. An estimation of the various enthalpic contributions demonstrates that the destruction of the coherence of the built-in water within the surfactant is decisive in the latter case. Two models corresponding to definite structures of the liquid crystalline mesophase of the surfactant show very satisfactory agreement with the experimental ΔH-values.     

Zum Mechanismus massenspektrometrischer Fragmentierungsreaktionen–II: Methoxygruppenwanderungen und Ringfragmentierungen in den Massenspektren der Methylather cyclischer Polyalkohole

The mass spectra of methyl ethers of cyclopentane-, cyclohexane- and cycloheptanediols contain a characteristic m/e 75 peak of ions of the structure ⊕CH(OCH₃)₂, which are formed by 1,3-, 1,4- or 1,5-migration of a methoxy group. The formation of these ions does not depend on the stereochemistry of the original molecule; probably the methoxy group migration occurs after α-cleavage of the molecular ion in an open chain radical ion: In the case of cycloalkanes with three or more methoxy groups the m/e 75 rearrangement ions give rise to one of the most prominent peaks of the mass spectra. Chemical bonds, terminating at a carbinol-C-atom, are weaker than normal. The presence of several carbinol-C-atoms in the molecular ions of cyclic polymethoxy compounds therefore favours fragmentations which differ from those of simple derivatives of cyclanols and which are typical of the position of the methoxy groups.