Roland Benoit

Fullerene core star-like polymers—1. Preparation from fullerenes and monoazidopolyethers

Abstract Monomethyl ethers of oligomeric polyoxyethylenes having azide end-groups were reacted with fullerenes (C60). Depending on the feed mole ratio, linear or star-like polymers were formed. The obtained fullerene-core star-like polymers (FCSP) were characterized by UV and FTIR spectroscopies, size-exclusion chromatography, vapor-pressure osmometry, thermogravimetric analysis, XPS measurements, and FAB-MS. The thermal stability of FCSP was higher than that of the starting polyethers. The thermal treatment of FCSP up to 1000°C did not lead to regeneration of C60. The FCSP gave stable emulsions of water-in-oil type in water/toluene system. FCSP showed herbicidal activity.

Characterization of diamond films deposited on titanium and its alloys

Abstract Titanium and its alloys have important applications for example in aerospace or as bioimplants. Some of these applications would be improved by diamond coatings. However the large thermal expansion mismatch between diamond and titanium or its alloys creates high residual stresses, up to about 7 GPa at 800 °C, which represent an important drawback. In this study, polycrystalline diamond films were deposited on pure titanium and Ti-6Al-4V in a classical tubular microwave plasma reactor from C-H(-O)-containing gas mixtures, at a temperature in the range 600–900 °C. Raman spectroscopy provided information about the diamond grain stress, which is obviously related to the deposition temperature. X-ray diffraction indicates the presence of titanium carbide or oxycarbide. Some other characterizations by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) are reported. It is shown that XPS coupled to argon ionic etching allows us to study the first steps of the deposition process. The structure and the chemical composition at the interface of a thicker deposit are obtained by TEM and EELS.

Magnetic nanocarriers of doxorubicin coated with poly(ethylene glycol) and folic acid: relation between coating structure, surface properties, colloidal stability, and cancer cell targeting

We report the efficient one-step synthesis and detailed physicochemical evaluation of novel biocompatible nanosystems useful for cancer therapeutics and diagnostics (theranostics). These systems are the superparamagnetic iron oxide nanoparticles (SPIONs) carrying the anticancer drug doxorubicin and coated with the covalently bonded biocompatible polymer poly(ethylene glycol) (PEG), native and modified with the biological cancer targeting ligand folic acid (PEG-FA). These multifunctional nanoparticles (SPION-DOX-PEG-FA) are designed to rationally combine multilevel mechanisms of cancer cell targeting (magnetic and biological), bimodal cancer cell imaging (by means of MRI and fluorescence), and bimodal cancer treatment (by targeted drug delivery and by hyperthermia effect). Nevertheless, for these concepts to work together, the choice of ingredients and particle structure are critically important. Therefore, in the present work, a detailed physicochemical characterization of the organic coating of the hybrid nanoparticles is performed by several surface-specific instrumental methods, including surface-enhanced Raman scattering (SERS) spectroscopy, X-ray photoelectron spectrometry (XPS), and time-of-flight secondary ion mass spectrometry (ToF-SIMS). We demonstrate that the anticancer drug doxorubicin is attached to the iron oxide surface and buried under the polymer layers, while folic acid is located on the extreme surface of the organic coating. Interestingly, the moderate presence of folic acid on the particle surface does not increase the particle surface potential, while it is sufficient to increase the particle uptake by MCF-7 cancer cells. All of these original results contribute to the better understanding of the structure-activity relationship for hybrid biocompatible nanosystems and are encouraging for the applications in cancer theranostics.

Influence of chemical modification of anthracite on the porosity of the resulting activated carbons

Activated carbons in a wide range of porosity (from essentially microporous to essentially mesoporous) have been prepared from anthracite by the combination of a chemical treatment with HClO or Mg(ClO ) and a physical activation 44 2 with CO at 8508C. The main effects of the chemical treatment are a modification of anthracite microstructure by insertion 2 and oxidation. The extent of these two reactions was found to be related to the nature of the chemical agents, the treatment time and temperature, and the textural properties of anthracite. As a consequence, the pretreatment of anthracite causes a noticeable reduction of the activation time and a change of the final pore size distribution. The influence of chemical treatment parameters has been analysed by means of XPS, FTIR, TGA, mass spectrometry, elemental analysis and gas adsorption techniques. The optimal conditions for producing activated carbons from chemically modified anthracites were identified. Step by step increasing of the temperature of anthracite treatment by HClO up to 1608C seems to be the best way 4 to obtain a precursor of highly activated carbon with well-balanced micro and meso porosity.

Perfluorofullerenes: Characterization and structural aspects

Abstract Characterization of highly fluorinated fullerenes (perfluorofullerenes) has revealed a wide range of x values. High reaction temperatures are limited by volatilization of the compounds. A good compromise is obtained for a reaction at 300 °C for several hours leading to a white C 60 F 54 compound with a narrow range of x values (± 2). X-ray powder diffraction reveals a f.c.c. lattice. Sublimation of C 60 F x compounds is carried out under static vacuum and separate fractions are condensed successively. As sublimation temperature is increased, fractions move from the liquid state to solids. 19 F NMR spectroscopy reveals a single narrow peak for liquid fractions, with a chemical shift of −72ppm/ CF 3 COOH thus suggesting a highly symmetrical species. The presence of oxygen is also detected when the starting material is exposed to air. The first fraction of air exposed compounds gives rise to a NMR signal at −55ppm. A relatively large quantity of liquid phase is obtained by direct condensation during C 60 fluorination. The NMR spectra is similar to that of the first sublimation fraction, exhibiting a peak at −72ppm.

Functionalization of multiwall carbon nanotubes: Properties of nanotubes-epoxy composites

Multiwall nanotubes were functionalized using plasma treatments, chemical oxidation, ball milling and thermal treatments. In optimized conditions, plasmas modify nanotubes surface chemistry with a great selectivity. Vickers microindentation and tension tests performed on epoxy resin loaded with multiwall nanotubes allow comparison of the influence of nanotubes surface chemistry and microtexture on loaded resin mechanical properties.

Clay/carbon nanocomposites as precursors of electrode materials for lithium-ion batteries and supercapacitors

Abstract Chars prepared by pyrolysis of organic precursors (Indoine Blue, Safranine, Pyrene) in the interlayer space of taeniolite were used as electrode materials in lithium/carbon cells. Due to oxidation of interlayer carbon by the silicate host, they contain a high amount of surface groups, and their essentially mesoporous character is attributed to the space liberated by the elimination of the clay template. A large reversible capacity for lithium insertion, up to 900 mAh/g, was detected for these materials. The chars presented a high capacitance which could reach 85 F/g in KOH electrolyte if they were formed below 850°C. Such a high value relatively to the low BET surface area of the chars is strictly related to the important mesopore volume and to the rich surface functionality.

Functionalisation of carbon nanotubes for composites

Catalytic multiwall carbon nanotubes (MWNT) were functionalized by low-pressure ammonia plasma and chemical oxidation, and their surface groups were identified by X-ray Photoelectron Spectroscopy (XPS) and acid-base titration. The reactivity of MWNT with ammonia plasma largely depends on their microtexture and on residual oxygen pressure in the reactor. Using catalytic MWNT presenting numerous dangling bonds on their outer part, the N/C atomic ratio could reach 0.18. Oxidation by sodium chlorate was very efficient (O/C atomic ratio=0.2) for the creation of surface carboxylic groups.

Comparison of Zirconium Phosphonate-Modified Surfaces for Immobilizing Phosphopeptides and Phosphate-Tagged Proteins

Different routes for preparing zirconium phosphonate-modified surfaces for immobilizing biomolecular probes are compared. Two chemical-modification approaches were explored to form self-assembled monolayers on commercially available primary amine-functionalized slides, and the resulting surfaces were compared to well-characterized zirconium phosphonate monolayer-modified supports prepared using Langmuir-Blodgett methods. When using POCl3 as the amine phosphorylating agent followed by treatment with zirconyl chloride, the result was not a zirconium-phosphonate monolayer, as commonly assumed in the literature, but rather the process gives adsorbed zirconium oxide/hydroxide species and to a lower extent adsorbed zirconium phosphate and/or phosphonate. Reactions giving rise to these products were modeled in homogeneous-phase studies. Nevertheless, each of the three modified surfaces effectively immobilized phosphopeptides and phosphopeptide tags fused to an affinity protein. Unexpectedly, the zirconium oxide/hydroxide modified surface, formed by treating the amine-coated slides with POCl3/Zr(4+), afforded better immobilization of the peptides and proteins and efficient capture of their targets.