No abstract

Hybrid nanostructured arrays based on carbon nanotubes (CNT) and palladium or titanium dioxide materials have been synthesized using self-supported and silicon-supported anodized aluminum oxide (AAO) as nanoporous template. It is well demonstrated that carbon nanotubes can be grown using these membranes and hydrocarbon precursors that decompose at temperatures closer to 600°C without the use of a metal catalyst. In this process, carbonic fragments condensate to form stacked graphitic sheets, which adopt the shape of the pores, yielding from these moulds' multi-walled carbon nanotubes. After this process, the ends of the tubes remain open and accessible to other substances, whereas the outer walls are protected by the alumina. Taking advantage of this fact, we have performed the synthesis of palladium and titanium dioxide nanostructures selectively inside carbon nanotubes using these CNT-AAO membranes as nanoreactors.

The synthesis and characterization of three novel ferrocenylphosphino sulfonates, namely ( 5-C 5 H 3 PR 2 (SO 3 i-Pr))Fe( 5-C 5 H 5) (R = Ph, p-Tol, Cy), is presented along with their solid-state X-ray crystal structures. Preliminary studies on the utility of these compounds as auxiliary ligands in aqueous catalysis, in particular for the rutheniumcatalyzed ortho-arylation of 2-phenylpyridine, are also discussed.

The hybrid structures composed of gold nanoparticles and carbon nanotubes were prepared using porous alumina membranes as templates. Carbon nanotubes were synthesized inside the pores of these templates by the non-catalytic decomposition of acetylene. The inner cavity of the supported tubes was used as nanoreactors to grow gold particles by impregnation with a gold salt, followed by a calcination-reduction process. The samples were characterized by transmission electron microscopy and X-ray energy dispersion spectroscopy techniques. The resulting hybrid products are mainly encapsulated gold nanoparticles with different shapes and dimensions depending on the concentration of the gold precursor and the impregnation procedure. In order to understand the electronic transport mechanisms in these nanostructures, their conductance was measured as a function of temperature. The samples exhibit a ‘non-metallic’ temperature dependence where the dominant electron transport mechanism is 1D hopping. Depending on the impregnation procedure, the inclusion of gold nanoparticles inside the CNTs can introduce significant changes in the structure of the tubes and the mechanisms for electronic transport. The electrical resistance of these hybrid structures was monitored under different gas atmospheres at ambient pressure. Using this hybrid nanostructures, small amounts of acetylene and hydrogen were detected with an increased sensibility compared with pristine carbon nanotubes. Although the sensitivity of these hybrid nanostructures is rather low compared to alternative sensing elements, their response is remarkably fast under changing gas atmospheres.

1,2,3-And 1,2,4-trisubstituted cyclopentadienyl manganese tricarbonyl compounds have been synthesized regioselectively from furans following a common synthetic strategy. The key steps include the transformation of furylcarbinols into hydroxycyclopentenones followed by the conjugate addition of Grignard reagents under chelation directed conditions. This affords hydroxycyclopentanones which can be dehydrated to cyclopentenones. These compounds are further elaborated into the final targets by the 1,2addition of organolithium reagents.