X-ray diffraction as a tool for the determination of the structure of double-walled carbon nanotube batches

The average structure of double-walled carbon nanotube DWCNT samples can be determined by x-ray diffraction XRD. We present a formalism that allows XRD patterns of DWCNTs to be simulated and we give researchers the tools needed to perform these calculations themselves. Simulations of XRD patterns within this formalism are compared to experimental data obtained on two different DWCNT samples, produced by chemical vapor deposition or by peapod conversion i.e., high-temperature peapod annealing. For each sample, we are able to determine structural aspects such as the number of walls, the diameter distribution of inner and outer tubes, the intertube spacing, and the bundled structure

Critical role of surface chemical modifications induced by length shortening on multi-walled carbon nanotubes-induced toxicity.

International audienceABSTRACT: Given the increasing use of carbon nanotubes (CNT) in composite materials and their possible expansion to new areas such as nanomedicine which will both lead to higher human exposure, a better understanding of their potential to cause adverse effects on human health is needed. Like other nanomaterials, the biological reactivity and toxicity of CNT were shown to depend on various physicochemical characteristics, and length has been suggested to play a critical role.We therefore designed a comprehensive study that aimed at comparing the effects on murine macrophages of two samples of multi-walled CNT (MWCNT) specifically synthesized following a similar production process (aerosol-assisted CVD), and used a soft ultrasonic treatment in water to modify the length of one of them.We showed that modification of the length of MWCNT leads, unavoidably, to accompanying structural (i.e. defects) and chemical (i.e. oxidation) modifications that affect both surface and residual catalyst iron nanoparticle content of CNT. The biological response of murine macrophages to the two different MWCNT samples was evaluated in terms of cell viability, pro-inflammatory cytokines secretion and oxidative stress. We showed that structural defects and oxidation both induced by the length reduction process are at least as responsible as the length reduction itself for the enhanced pro-inflammatory and pro-oxidative response observed with short (oxidized) compared to long (pristine) MWCNT.In conclusion, our results stress that surface properties should be considered, alongside the length, as essential parameters in CNT-induced inflammation, especially when dealing with a safe design of CNT, for application in nanomedicine for example

Large specific surface area in highly crystalline Silicon Carbide (SiC) from templated poymeric precursors

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Etude structurale et vibrationnelle de composés à base de nanotubes de carbone : nanotubes bifeuillets, peapods et composés ternaires.

This work is dedicated to the structural and vibrationnal properties of carbon nanotube based molecular compounds: double-walled carbon nanotubes, peapods and ternary compounds. In the first part of the manuscript, the structure of these compounds is studied by X-ray and neutron powder diffraction. The diffraction patterns are numerically calculated, and comparisons between numerical and experimental results allow to determine the structure of these compounds. In the second part of this work, the dynamical properties of peapods and double-walled carbon nanotubes are studied by inelastic neutron scattering. The experimental phonon densities of states of peapods and double-walled carbon nanotubes are compared with the results of lattice dynamics calculations, performed for different structural hypothesis (in the case of peapods, C60 stacked as monomer chains, as dimer chains or as polymeric chains).Ce travail de thèse est dédié aux propriétés structurales et vibrationnelles de composés moléculaires comportant des nanotubes de carbone: nanotubes bifeuillets, peapods et composés ternaires. Dans la première partie de ce manuscrit, la structure de ces composés est étudiée par diffraction de poudre des rayons X et des neutrons. Les diagrammes de diffraction sont calculés numériquement et des comparaisons entre résultats numériques et résultats expérimentaux permettent de résoudre précisément la structure des composés. Dans la seconde partie de ce travail, les propriétés dynamiques des peapods et des nanotubes bifeuillets sont étudiées par diffusion inélastique des neutrons. Les densités d'états de phonons expérimentales sont comparées avec les résultats de dynamique des réseaux effectués pour différentes hypothèses structurales (dans le cas des peapods, chaînes de C60 insérées dans les nanotubes sous forme de monomères, de dimères ou de polymères)

Étude structurale et vibrationnelle de composés à base de nanotubes de carbone (nanotubes bifeuillets, peapods et composés ternaires)

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Systèmes unidimensionnels de fullerènes C60 et C70 confinés dans les nanotubes de carbone (transformations structurales et dynamique)

ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Multi-method analysis of functionalized single-walled carbon nanotubes for cesium liquid–solid extraction

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Soft templated mesoporous SiC from polycarbosilane grafted onto triblock copolymers

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Aggregation of semifluorinated alkanes in cyclic organic solvents: A SAXS study

International audienceSemifluorinated alkanes (SFA) are diblock molecules able to self-assemble in various organic media due to their fluorophilic/fluorophobic interactions. Such mixtures accordingly represent a model system for the further elaboration of soft-templated inorganic materials in totally anhydrous media. The aggregation behavior of four SFA species has been studied in two different organic and cyclic solvents in function of temperature by small angle X-ray scattering (SAXS). As long as the SFA-solvent mixtures remain in the liquid state, SAXS patterns reveal an aggregation behavior dependent on temperature and concentration, and on the internal structure of the SFA. We identify the relevant parameters governing the aggregation of these molecules based on the simulation of SAXS data versus temperature