Search results for "Surfaces"

New materials with high spin polarization: half-metallic Heusler compounds

2007

Effects of Metal-Organic Chemical Vapour Deposition grown seed layer on the fabrication of well aligned ZnO nanorods by Chemical Bath Deposition

2011

Well aligned, long and uniform ZnO nanorods have been reproducibly fabricated adopting a two-steps Metal-Organic Chemical Vapour Deposition (MOCVD) and Chemical Bath Deposition (CBD) fabrication approaches. Thin (<100 nm) ZnO buffer layers have been seeded on silicon substrates by MOCVD and ZnO layers have been subsequently grown, in form of well textured nanorods, using CBD. It has been found that the structure and thickness of the seed layer strongly influence the final morphology and the crystal texturing of ZnO nanorods as well as the CBD growth rate. There is, in addition, a strong correlation between morphologies of CBD grown ZnO nanorods and those of the seed layer underneath. Thus, …

Facile formation of a meso–meso linked porphyrin dimer catalyzed by a manganese(iv)–oxo porphyrin

2011

A manganese(IV)-oxo porphyrin catalyzes C-C bond formation between zinc porphyrins at the meso-position with a two-electron oxidant to afford the meso-meso linked porphyrin dimer efficiently. The meso-meso linked dimer is formed via formation of the porphyrin radical cation, and the rate-determining step in the catalytic cycle is the formation of a manganese(IV)-oxo porphyrin with a two-electron oxidant.

Chemical and electrochemical behaviour of 4,4’,4’’,4’’’-tetrakis(dimethylamino)-tetraphenylethylene in an oxidant environment: Toward a new sensor fo…

2020

Abstract Electrochromic compounds are suitable candidates for being used in sensor design. Here we report the use of 4,4’,4’’,4’’’-tetrakis(dimethylamino)-tetraphenylethylene for detecting both NO2 and SO2. Whereas the sensing mechanism in the case of nitrogen dioxide is a simple chemical oxidation reaction, in the case of sulfur dioxide, the mechanism is much more complex and the reaction requires the presence of t-butylhydroperoxide to take place. By modifying the detection conditions both compounds can be detected in gas phase. Additionally, a wide electrochemical study has been carried out to understand the role played by the t-butylhydroperoxide in the reaction with sulfur dioxide.

Electro-optical spectroscopy on aggregated chromophore systems in Langmuir-Blodgett films

1992

Linear and quadratic Stark spectra were measured on LB films that contained a hydrophobically substituted cyanine chromophore in binary mixtures with arachidic acid. The external field was applied normal or parallel to the film surface on samples with different internal symmetry. It was found that the orientation of the symmetry axis of the dye molecule is close to the surface normal. A significant number of molecules, 5–10%, are flipped head-to-tail from the main orientation. Parallel to the film surface, large polarizability changes on electronic excitation, Δα ∼ 1000 A3, were observed that reflect electron delocalization over aggregates. At low dye concentrations, large internal electric…

Mixed silane self assembled monolayers and their in situ modification

1998

Mixed self assembled silane monolayers were prepared by coadsorption of Br and methyl terminated trichlorosilanes. By subsequent in situ modification the Br groups were converted into amino groups which can be used to tether polyglutamates to the surface. Here we describe the characterization of the monolayers by means of contact angle measurements and X-ray photoelectron spectroscopy (XPS). Both methods clearly indicate that the Br terminated silane is preferentially adsorbed from the solution. Following the in situ modification by XPS a yield of approximately 80% was determined for the substitution of the bromine by azide, whereas the yield for subsequent reduction to the amine is close t…

Template-controlled synthesis of chiral cyclohexylhemicucurbit[8]uril

2015

Enantiomerically pure cyclohexylhemicucurbit[8]uril (cycHC[8]), possessing a barrel-shaped cavity, has been prepared in high yield on a gram scale from either (R,R,N,N')-cyclohex-1,2-diylurea and formaldehyde or cycHC[6]. In either case, a dynamic covalent library is first generated from which the desired cycHC can be amplified using a suitable anion template.

Synthesis of huge macrocycles using two calix[4]arenes as templates.

2005

Macrocycles with up to 100 atoms have been synthesised using two calix[4]arenes as templates: first, (3,5-dialkenyloxy)phenyl groups are attached to the wide rim of a calix[4]arene via urea links, then the alkenyl groups are connected via a metathesis reaction using a tetratosylurea calix[4]arene for their correct prearrangement and finally the urea functions are cleaved to detach the newly formed macrocycles.

Gold(ii) in redox-switchable gold(i) catalysis

2019

Chemical communications 55(32), 4615 - 4618 (2019). doi:10.1039/C9CC00283A

A post-synthetic approach triggers selective and reversible sulphur dioxide adsorption on a metal-organic framework.

2018

We report the application of a post-synthetic solid-state cation-exchange process to afford a novel 3D MOF with hydrated barium cations hosted at pores able to trigger selective and reversible SO2 adsorption. Computational modelling supports the full reversibility of the adsorption process on the basis of weak supramolecular interactions between SO2 and coordinated water molecules.