Pierre R. Marcoux

A spectroscopic study of the fluorination and defluorination reactions on single-walled carbon nanotubes

The manipulation of isolated single-wall carbon nanotubes (SWNTs), rather than bundles, has led to active research in the field of the functionalisation of such carbon compounds. Different ways exist today to obtain some new soluble macromolecules from SWNTs. Here we focus on the fluorination functionalisation. As the solubility properties depend essentially on the degree of functionalisation, it is important to develop reliable and simple methods to quantify this. The CnF stoichiometry of three different fluorinated SWNTs samples are determined with X-ray photoelectron spectroscopy (XPS). Then the evolution of the Raman spectra with the degree of fluorination of these samples is discussed. An atomic force microscopy (AFM) study highlights the good solvation properties of the most fluorinated sample with a majority of isolated nanotubes being observed. Then we take advantage of these good solvation properties, combined with the possibility of recovering the pristine non-fluorinated nanotubes, to carry out surface enhanced Raman spectroscopy (SERS) studies of well-dispersed SWNTs. These studies put in evidence the bundle effect, which is due to the agglomeration of SWNTs into bundles. This effect can be readily observed by Raman spectroscopy.

Core–shell structure of chemically synthesised FePt nanoparticles: a comparative study

We carried out solution synthesis of FePt nanoparticles through different chemical methods, using four “hot soap methods”, i.e. particle formation in the presence of surfactant molecules at high temperatures, and one polyol process. Structural and magnetic properties of the as-made particles pointed to a core–shell structure for the particles prepared with hot soap methods, with an iron-depleted core surrounded by a pure iron shell. Such a structure has an impact on the magnetic properties of as-made particles since Fe atoms from the shell are oxidised and non magnetic. We proved however that iron atoms of this shell are available during the formation of the ordered phase upon annealing: L10 phase for small particles, L12 for bigger ones. In contrast, the core–shell structure was not observed in the case of nanoparticles synthesised according to the polyol process. This outlines the key role of the stabilising ligands, long alkyl chain surfactants in the former case and tetraethylene glycol in the latter.

Surface Enhanced Raman Scattering on Fluorinated Single Wall Carbon Nanotubes

In the following paper we will describe a method to produce substrates with thin films of silver or gold which are particularly active for Surface Enhanced Raman Scattering (SERS). These substrates are used to perform a new deposition process of reversibly functionalized SWNTs which permits to obtain isolated SWNTs on SERS surfaces. These studies put in evidence the bundle effect, which is due to agglomeration of SWNTs into bundles.

Functionalized nanoporous materials for volatile metabolites monitoring with direct optical transduction

A noninvasive and low cost colorimetric test is proposed to detect microorganisms in complex media via volatile metabolites released by enzymatic activity. The sensor is based on a hybrid organic-inorganic nanoporous xerogel. This transparent and colorless silica matrix traps and concentrates targeted volatile metabolites which are then detected by absorbance measurements. Ortho-nitrophenol was chosen as a volatile metabolite. At a first stage, the trapping efficiencies of various functionalized xerogels were compared in order to optimize the detection of ortho-nitrophenol. As a second step, we used xerogels with the best composition to detect E. coli cells in blood samples.