Jean-François Colomer

Large-scale synthesis of single-wall carbon nanotubes by catalytic chemical vapor deposition (CCVD) method

The large-scale production of single-wall carbon nanotubes (SWNTs) is reported. Large quantities of SWNTs can be synthesised by catalytic decomposition of methane over well-dispersed metal particles supported on MgO at 1000°C. The thus produced SWNTs can be separated easily from the support by a simple acidic treatment to obtain a product with high yields (70–80%) of SWNTs. Because the typical synthesis time is 10 min, 1 g of SWNTs can be synthesised per day by this method. The SWNTs are characterized by high-resolution transmission electron microscopy and by Raman spectroscopy, showing the quality and the quantity of products.

Control of the outer diameter of thin carbon nanotubes synthesized by catalytic decomposition of hydrocarbons

Abstract Multi-wall carbon nanotubes have been produced by the catalytic decomposition of acetylene. Co–Mo, Co–V and Co–Fe mixtures supported either on zeolite or corundum alumina were used as catalysts. When Fe or V is added to Co, the carbon deposit increases. The nanotubes were characterized by both low and high resolution TEM. From histograms representing the outer diameter distributions, it is clear that the outer diameter of the nanotubes can be controlled by choosing the appropriate catalyst.

Different purification methods of carbon nanotubes produced by catalytic synthesis

Different purification methods of carbon nanotubes produced by catalytic process are described, based on the reactivity differences between carbon nanotubes and impurities (principally amorphous carbon). The quality, but also the major modifications of the nanotubes caused by these treatments are investigated by transmission electron microscopy.

Purification of catalytically produced multi-wall nanotubes

Carbon nanotubes were produced in large amounts by catalytic decomposition of acetylene over a Co incorporated zeolite NaY support. Purification of multi-wall nanotubes was required in order to eliminate catalyst and amorphous carbon produced by thermal decomposition of hydrocarbon. First, separation of nanotubes and catalyst particles was carried out by hydrofluoric acid treatment. Then, two ways of removing amorphous carbon were studied: permanganate oxidation and air oxidation. The quality of nanotubes was characterized by means of transmission electron microscopy and the yield of pure nanotubes was quantitatively determined. Changes caused by treatment of the nanotubes were investigated by high resolution electron microscopy and a comparison was made between the nanotubes produced by this method and those synthesized by an arc discharge process after oxidation treatment.

Segmented and opened multi-walled carbon nanotubes

Cutting multi-walled carbon nanotubes and letting them open is a key issue for potential applications which imply insertion of chemical species. This is performed by using a new, clean, and simple abrasive method involving diamond particles. Direct observation of the treated sample by transmission electron microscopy reveals fragments of tubes with lengths ranging from 200 to 600 nm and opened on both of their ends. X-ray diffraction and micro-Raman spectroscopy attest that tubes keep their initial structure confirming that the proposed method does not induce drastic structural damage.

Titanium oxide nanoribbons

Thin titanium oxide nanoribbons with a thickness of several nanometers and a width of 30–200 nm have been synthesized hydrothermally via the reaction of TiO2 particles and NaOH solution. Either amorphous TiO2 gel or crystalline anatase or a mixture of anatase and rutile can be used as the raw material. The typical lengths of nanoribbons are in the range of several micrometers to several tens of micrometers. The growth of nanoribbons is along the [0 0 1] direction of the anatase structure. 2002 Elsevier Science B.V. All rights reserved.

Functionalization of vertically aligned carbon nanotubes

Summary This review focuses and summarizes recent studies on the functionalization of carbon nanotubes oriented perpendicularly to their substrate, so-called vertically aligned carbon nanotubes (VA-CNTs). The intrinsic properties of individual nanotubes make the VA-CNTs ideal candidates for integration in a wide range of devices, and many potential applications have been envisaged. These applications can benefit from the unidirectional alignment of the nanotubes, the large surface area, the high carbon purity, the outstanding electrical conductivity, and the uniformly long length. However, practical uses of VA-CNTs are limited by their surface characteristics, which must be often modified in order to meet the specificity of each particular application. The proposed approaches are based on the chemical modifications of the surface by functionalization (grafting of functional chemical groups, decoration with metal particles or wrapping of polymers) to bring new properties or to improve the interactions between the VA-CNTs and their environment while maintaining the alignment of CNTs.

Synthesis of single-wall carbon nanotubes by catalytic decomposition of hydrocarbons

Individual single-wall carbon nanotubes (SWNTs) and bundles can be obtained over different types of supported metal catalysts by decomposition of ethylene, similar to the synthesis of multi-wall carbon nanotubes.

Graphene-coated holey metal films: Tunable molecular sensing by surface plasmon resonance

We report on the enhancement of surface plasmon resonances in a holey bidimensional grating of subwavelength size, drilled in a gold thin film coated by a graphene sheet. The enhancement originates from the coupling between charge carriers in graphene and gold surface plasmons. The main plasmon resonance peak is located around 1.5 μm. A lower constraint on the gold-induced doping concentration of graphene is specified and the interest of this architecture for molecular sensing is also highlighted.

Characterization of single-wall carbon nanotubes produced by CCVD method

Abstract Carbon single-wall nanotubes (SWNTs) can be produced by the catalytic chemical vapor deposition (CCVD) method. They are synthesized by catalytic decomposition of methane at 1000 °C on 2.5 wt% Co/MgO catalyst. SWNT samples have been characterized by transmission electron microscopy (TEM) and Raman spectroscopy. Using these two techniques, a comparison between the SWNTs produced by CCVD and synthesized by electric arc discharge has been made. Finally, we give conclusions about the diameter distribution and the electronic structure of SWNTs produced by the CCVD method.