Modifications of single-wall carbon nanotubes upon oxidative purification treatments

A systematic characterization of single-wall carbon nanotube (SWCNT) material after successive purification steps, including reflux treatment with nitric acid, air oxidation, and annealing, has been performed. Inductively coupled plasma–optical emission spectroscopy shows that a considerable reduction of the metal impurities by up to 95% can be obtained by the nitric acid reflux treatment. During this process, Raman spectroscopy clearly proves that HNO3 molecules are intercalated into the bundles of SWCNTs. At the same time, SWCNTs have suffered a high degree of degradation and defects are being introduced. The subsequent thermal processes lead to the removal of further defect carbon materials and to the almost complete de-intercalation of the HNO3 molecules. Transmission electron microscopy reveals that the remaining SWCNT bundles tend to form thick bundles. Thus the applied purification process results in a high-purity SWCNT material with a drastically reduced content of metal nanoparticles and composed of large bundles of SWCNTs.This work was supported by the European Commission under the Research Training Network contract NANOCOMP (HPRN-CT-2000-00037).Peer reviewe

Sensitivity of single wall carbon nanotubes to oxidative processing: structural modification, intercalation and functionalisation

The effect of oxidation on modification of single wall carbon nanotubes (SWCNTs) through successive purification steps has been studied. The efficient elimination of metal impurities has been followed by induced coupled plasma spectroscopy. Upon acid treatment, Raman spectroscopy clearly proofed that HNO3 molecules were intercalated into the bundles of SWCNTs. At the same time, SWCNTs also have suffered a high degree of degradation and defects were introduced. The subsequent thermal processes led to the removal of further defect carbon materials and to the almost complete de-intercalation of the HNO3 molecules. Changes in the structure of the SWCNT bundles have been observed by transmission electron microscopy. While bundles tend to separate upon acid treatment, after the complete purification process, the remaining SWCNTs tend to form thick bundles again. The existence of functional groups in the raw single wall carbon nanotubes material and their modification and almost complete removal after the final annealing step has been studied by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and temperature programmed desorption. Nitrogen adsorption isotherms analysed according to Brunauer–Emmet–Teller showed important changes in the pore volume and surface area through the purification steps.This work was supported by the European Commission under the Research Training Network contract NANOCOMP (HPRN-CT-2000-00037).Peer reviewe

Indoor air quality and comfort in seven newly built, energy-efficient houses in France

International audienceA field survey was carried out in seven newly built energy-efficient houses in France. Several indoor air-quality indicators (total volatile organic compounds, volatile organic compounds, aldehydes, carbon monoxide, particulate matter less than 2.5 micrometre in diameter (PM2.5) and radon) and indoor environmental parameters (carbon dioxide, temperature, relative humidity and noise) were measured before and during the houses' first year of occupancy. The air exchange per hour (ACH) and air exhaust rate were measured simultaneously, and the perceptions of the occupants were evaluated with a questionnaire. The results show that the levels of aromatic hydrocarbons, terpenes, alkanes and aldehydes were higher before occupancy than during occupancy, whereas the opposite trend was observed for PM2.5. During occupation, the concentrations of acetaldehyde, alpha-pinene, ethylbenzene, limonene, styrene, toluene and xylenes decrease, most likely because of the decrease in emissions sources from houses. At the same time, the levels of benzene, formaldehyde, hexaldehyde, n-decane and n-undecane temporarily increase because of human activities. The PM2.5 levels show seasonal variation. Compared to standard French houses, the concentrations of benzene, ethylbenzene, m- and p-xylenes, PM2.5 and radon were low, whereas the CO2 and formaldehyde levels were not significantly different. In contrast, the levels of acetaldehyde, hexaldehyde, n-decane, n-undecane, oxylene and styrene were higher in these new homes, possibly because of the emissions from products and materials. Mechanical ventilation with heat-recovery systems allows for ACH levels of 0.5 h-1 or higher, making the air drier. Shortcomings of the system are also reported

Synthesis of a new polyaniline/nanotube composite: “In-situ” polymerisation and charge transfer through site-selective interaction

A new polyaniline/multi-wall carbon nanotube (PANI/MWNT) composite has been successfully synthesized by an “in-situ” polymerisation process; Raman studies indicate a site-selective interaction between the quinoid ring of the polymer and the MWNTs opening the way for charge transfer processes; transport measurements clearly reveal drastic changes in the electronic behaviour confirming the formation of a true composite material with enhanced electronic properties.This work was supported by the EC RTN contract NANOCOMP (HPRN-CT-2000-00037).Peer reviewe

Méthodologie Pour Comparer Différentes Méthodes D'extraction De Biomarqueurs Sans Méthode De Référence. Application À La Segmentation Du Ventricule Gauche En Irm Cardiaque Pour Estimer La Fraction D'éjection.

International audienceUne méthodologie est proposée pour comparer plusieurs méthodes d’estimation d’un paramètre d’intérêt clinique sans connaître de gold standard. Elle est appliquée à un problème de comparaison de la fraction d’éjection du ventricule gauche en IRM cardiaque obtenue par sept approches de segmentation différentes et appliquée à 30 examens issus de la base de données constituée pour le challenge Miccai 2009 de segmentation du ventricule gauche. La comparaison des méthodes montre une supériorité du tracé manuel, un bon comportement des méthodes de segmentation semi-automatiques et un plus mauvais comportement des méthodes plus largement automatisées. La méthodologie de comparaison proposée qui ne fait aucun a priori sur les méthodes retrouve ainsi l’ordre attendu. Cette approche méthodologique est donc pertinente et doit permettre une classification non supervisée de différentes méthodes d’estimation de biomarqueurs