Determination of certain VOCs in paints and architectural coatings by dynamic headspace gas chromatography-mass spectrometry.

A quantitative method for the determination of the following VOCs: acetone, dichloromethane, dimethyl carbonate, methyl acetate, tertiary butyl acetate, chlorobenzotrifluoride (4-CBTF) and propylene carbonate in paints was developed in support of Environment and Climate Change Canada's Automotive Refinishing Product and Architectural Coatings VOC Concentration Limits regulations. These compounds are excluded from the VOC definition by Canadian Environmental Protection Act (CEPA) regulations, and their content do not contribute to the overall VOC content in products for regulatory purposes. The method is based on Dynamic Headspace GC-MS. It was determined that activated carbon is the best trapping medium for these compounds. The technique has been compared to a currently used direct injection technique, with comparable results. Contrary to the direct injection method which requires complex sample handling prior to injection in the gas chromatograph, the dynamic headspace method practically eliminates the need for sample handling allowing for much shorter sample turnover and reducing the possibility of sampling handling errors.

Reaction of CO2 with a Vanadium(II) Aryl Oxide: Synergistic Activation of CO2 /Oxo Groups towards H-Atom Radical Abstraction.

Treatment of divalent (ONNO)V(TMEDA) (1; ONNO=[2,4-Me2 -2-(OH)C6 H2 CH2 ]2 N(CH2 )2 NMe2 ) with CO2 afforded [(ONNO)V]2 (µ-OH)(µ-formate) (2). Whereas the bridging hydroxo and formate groups both originated from CO2 , the H atoms present on the two residues were obtained through H-atom radical abstraction from the solvent. DFT calculations revealed an initially linear CO2 bonding mode, followed by deoxygenation, and highlighted a synergistic effect between the so-formed oxo group and an additional bridging CO2 residue in promoting radical behavior.

Radical Behavior of CO2 versus its Deoxygenation Promoted by Vanadium Aryloxide Complexes: How the Geometry of Intermediate CO2 -Adducts Determines the Reactivity.

The reactivity of carbon dioxide with vanadium(III) aryloxo complexes has been investigated. The formation of either carbon monoxide or incorporation into the ligand system with the ultimate formation of organic ester was observed depending on the overall electron donor ability of the ligand field. DFT calculations were carried out to investigate the proposed mechanism for carbon dioxide coordination and reduction.

Revisiting the behaviour of BiVO4 as a carbon dioxide reduction photo-catalyst.

Bismuth vanadate is a widely known photocatalyst for the hydro-reduction of CO2. In spite of the great appeal of such a catalytic system, problems arise due to deactivation of the catalyst with consequent low reaction yield. We have investigated the catalyst behavior during methanol production and have found that the catalyst irreversibly loses vanadium from the structure whilst depositing bismuth oxides on the surface of the catalyst. While catalyst activity can be restored upon heating, leaching of vanadium, leading in long term to catalyst decomposition, is unavoidable and irreversible.

Photon tunneling into a single-mode planar silicon waveguide.

We demonstrate the direct excitation of a single TE mode in 25 nm thick planar crystalline silicon waveguide by photon tunneling from a layer of fluorescent dye molecules deposited by the Langmuir-Blodgett technique. The observed photon tunneling rate as a function of the dye-silicon separation is well fitted by a theoretical tunneling rate, which is obtained via a novel approach within the framework of quantum mechanics. We suggest that future ultrathin crystalline silicon solar cells can be made efficient by simple light trapping structures consisting of molecules on silicon.