Authors: O. Raccurt, J. Samuel, O. Poncelet, S. Szenknect, F. Tardif
Affilation: Laboratory of Tracers Technologies, France
Pages: 704 - 707
Keywords: nanotracers, nanoparticules, fluorescence, surface fonctionalization, transport colloïdal particles
Optical and magnetic nanoparticles are both attractive fields of investigation which are gaining in importance due to their potential markets e.g. polymer nano-composite, colloidal dispersion, environmental monitoring or biomedical diagnostics, etc. Among all the spectroscopic mechanisms used in order to monitor tracers, fluorescence is the most attractive because of its simplicity to use and inherently low detection limits. A very large set of fluorescent particles can be bought or synthesized thanks to recent progress in nanotechnologies. Their diameter, their surface functionalization, their spectral signature can be tailored for specific applications. For instance, these fluorescent nanotracers with controlled size and surface properties offer an interesting potential for different application such as nanofiller homogeneity monitoring in polymer composite, characterization of colloidal stabilirty in liquids and colloidal transport in porous media. In all the case, nanotracers may be constituted by engineered fluorescent particles presenting the same behavior as the colloids of interest (with peculiar size, density and zeta potential). - For the first application, dispersion of nanoparticles such as luminescent silica or nano-clays into polymer has been studied by measurement of the fluorescence. Fluorescent silica nanoparticles have been synthesized by sol-gel micro-emulsion process (Fig 1). The hydrophobic or hydrophilic surface properties are controlled by the covalent bounding of different molecules. For nano-clays, the intercalation of the fluorescent organic dyes into natural clay is studied. This fluorescent nano-clays are used to monitoring the mixing and the exfoliation process during extrusion. - The second application concerns the characterization of the dispersion and the colloidal stability in different solvent. In this part we will present the impact of the surface properties on the dispersion of fluorescent silica nanoparticle into polymeric material. - Finally the silica fluorescent nanoparticle are using for tracing the colloidal transport into the soil. Recent field and laboratory experiments have identified colloid-facilitated transport of contaminants as an important mechanism of contaminant migration through groundwater. To demonstrate the existence of colloid-facilitated transport, three criteria must be fulfilled: (1) soil colloidal particles must be mobilized; (2) pollutants must associate with the colloids and (3) colloids must be transported through the porous media. Our aim is to determine the physicochemical conditions that lead to soil colloid generation and transport in a heterogeneous porous media and compare them with the classical mobilization theory. As this theory hardly fits to natural heterogeneous porous media, we propose to use new colloidal tracers to simulate the transport of natural particles. The silica fluorescent nano-colloids, reproduce the main characteristics of the mobilizable soil particles (their size, density and zeta potential) and incorporate fluorescent dyes to be detected by fluorescence measurements (Fig 2).