Quantification and prediction of water uptake by soot deposited on ventilation filters during fire events.

Soot samples from different fuels were produced in small and pilot combustion test benches at various O concentrations, and were then characterized in terms of primary particle diameter, specific surface area and oxygen content/speciation. Water sorption measurements were then carried out for soot compacted into pellet form and in powder form, using both a gravimetric microbalance and a manometric analyser. Water adsorption isotherms are all found to be Type V, and reveal the central role of the specific surface area and the oxygen content of soot.

How the Intricate Interactions between Carbon Nanotubes and Two Bilirubin Oxidases Control Direct and Mediated O2 Reduction.

Due to the lack of a valid approach in the design of electrochemical interfaces modified with enzymes for efficient catalysis, many oxidoreductases are still not addressed by electrochemistry. We report in this work an in-depth study of the interactions between two different bilirubin oxidases, (from the fungus Myrothecium verrucaria and from the bacterium Bacillus pumilus), catalysts of oxygen reduction, and carbon nanotubes bearing various surface charges (pristine, carboxylic-, and pyrene-methylamine-functionalized). The surface charges and dipole moment of the enzymes as well as the surface state of the nanomaterials are characterized as a function of pH.

Surface-enhanced nitrate photolysis on ice.

Heterogeneous nitrate photolysis is the trigger for many chemical processes occurring in the polar boundary layer and is widely believed to occur in a quasi-liquid layer (QLL) at the surface of ice. The dipole-forbidden character of the electronic transition relevant to boundary layer atmospheric chemistry and the small photolysis/photoproduct yields in ice (and in water) may confer a significant enhancement and interfacial specificity to this important photochemical reaction at the surface of ice. Using amorphous solid water films at cryogenic temperatures as models for the disordered interstitial air-ice interface within the snowpack suppresses the diffusive uptake kinetics, thereby prolonging the residence time of nitrate anions at the surface of ice.

Proton transfer reactions between nitric acid and acetone, hydroxyacetone, acetaldehyde and benzaldehyde in the solid phase.

The heterogeneous and homogeneous reactions of acetone, hydroxyacetone, acetaldehyde and benzaldehyde with solid nitric acid (HNO(3)) films have been studied with Reflection-Absorption Infrared Spectroscopy (RAIRS) under Ultra-High Vacuum (UHV) conditions in the 90-170 K temperature range. In the bulk or at the surface of the films, nitric acid transfers its proton to the carbonyl function of the organic molecules, producing protonated acetone-H(+), hydroxyacetone-H(+), acetaldehyde-H(+) and benzaldehyde-H(+), and nitrate anions NO(3)(-), a reaction not observed when nitric acid is previously hydrated [J. Lasne, C.

Adsorption of acetaldehyde on ice as seen from computer simulation and infrared spectroscopy measurements.

Detailed investigation of the adsorption of acetaldehyde on I(h) ice is performed under tropospheric conditions by means of grand canonical Monte Carlo computer simulations and compared to infrared spectroscopy measurements. The experimental and simulation results are in a clear accordance with each other. The simulations indicate that the adsorption process follows Langmuir behavior in the entire pressure range of the vapor phase of acetaldehyde.

Interaction of acetone, hydroxyacetone, acetaldehyde and benzaldehyde with the surface of water ice and HNO3·3H2O ice.

Oxygenated volatile organic compounds (OVOCs) influence the oxidative properties of the atmosphere, and their transport from the ground may occur by scavenging by the HNO(3)-rich supercooled water droplets found in polluted convective air masses. With infrared spectroscopy, we have studied the interactions of four typical atmospheric OVOCs (acetone, hydroxyacetone, acetaldehyde and benzaldehyde) with model surfaces of water ice and of trihydrated nitric acid (NAT) ice. We show that these molecules weakly adsorb on water ice and NAT by hydrogen bonding.

HCl adsorption on ice at low temperature: a combined X-ray absorption, photoemission and infrared study.

The reaction of HCl on water ice provides a simple case for understanding dissociation and proton transfer in this non-optimal, incomplete solvation environment, playing a central role in atmospheric chemistry. This reaction has been repeatedly reported as thermally dependent, whereas the theoretical models predict a spontaneous dissociation. We examine the adsorption of HCl on ice at low temperature (50 K and 90 K) via a combination of near-edge X-ray absorption spectroscopy (NEXAFS) at the chlorine L-edge, photoemission (XPS and UPS), and reflection-adsorption infrared spectroscopy (FT-RAIRS).