Elaboration de nanoparticules d'or fonctionnalisées pour la détection et l'imagerie biologiques

Gold nanoparticles seem to be ideal templates for immobilizing and carrying a high number of organic molecules. This property might have potential application in the field of microscopy by fluorescence and magnetic resonance imaging in order to lower the detection threshold. A study on this subject has also been launched and led to synthesis of gold nanoparticules (8-12 nm), functionnalized with several hundreds of fluorophores. A study performed on biochips demonstrated that these new luminescent nanoprobes have a real potential for the biological detection since signal is enhanced occur by two orders of magnitude. At the same time, the synthesis of gold nanoparticles (2-2.5 nm) surrounded by a multilayer of dithiolated derivatives (DTDTPA), especially stable in solution, are able to chelate gadolinium ions. MRI study of these nanoparticles reveal a significant enhancement of the contrast in comparison to DTPA:Gd.Les nanoparticules d'or représentent des plates-formes idéales pour l'immobilisation et le transport d'un nombre élevé de molécules organiques. Cette propriété revêt des applications potentielles en microscopie par fluorescence et en imagerie par résonance magnétique dans l'abaissement du seuil de détection. Une étude a donc été menée sur ce sujet aboutissant à la synthèse de nanoparticules d'or (8-12 nm), porteuses de plusieurs centaines de fluorophores. Une étude menée sur des puces ADN a ainsi démontré que ces nouvelles sondes luminescentes nanométriques possèdent un réel potentiel permettant d'abaisser le seuil de détection de deux ordres de grandeurs. Parallèlement, la synthèse de nanoparticules d'or (2-2,5 nm) recouvertes d'une multicouche d'un dérivé dithiolé (DTDTPA), particulièrement stables en solution ont permis la complexation d'ions gadolinium. L'étude IRM pratiquée sur ces nanoparticules révèle en effet une augmentation significative du contraste par rapport au DTPA:Gd

One-pot organometallic synthesis of well-controlled gold nanoparticles by gas reduction of Au(I) precursor: a spectroscopic NMR study

International audienceA stable colloidal solution of gold nanoparticles (AuNPs) has been prepared in tetrahydrofuran by gas reduction of AuCl(tetrahydrothiophene) and alkylamines (1-octylamine, 1-dodecylamine, and 1-hexadecylamine) as stabilizing agents. Carbon monoxide is a better reducing agent than hydrogen. The important parameters for control of the synthesis of AuNPs are the temperature, the molar ratio of ligand/metal, and the structure of the stabilizing agent. A high concentration of long alkyl chains (10 eq.) favours the control of the growth of AuNPs of defined size and shape with a diameter of 4.7 nm and a narrow size distribution. For the first time, liquid-state combined with solid-state NMR spectroscopies were used in order to determine the role of the long chain alkylamines in the synthesis of AuNPs in CO atmosphere. This combination enables the understanding of the complex chemistry of the surface of AuNPs involved in the stabilization of the AuNPs. Indeed, carbamide species were formed during the synthesis. They were strongly coordinated to the surface of AuNPs and exchange phenomena of the alkylamines present in solution occurred, too

PTA-stabilized ruthenium and platinum nanoparticles: characterization and investigation in aqueous biphasic hydrogenation catalysis

International audienceVery small ruthenium and platinum nanoparticles have been prepared from organometallic complexes by using 1,3,5-triaza-7-phosphaadamantane (PTA) as stabilizer, which allowed their easy dispersion into water. These nanoparticles were fully characterized by different techniques. In particular, the coordination of PTA to the surfaces of the particles was studied by NMR spectroscopy. The potential of these nanoparticles as catalysts was investigated in aqueous biphasic catalysis; olefins and arene derivatives were hydrogenated under mild conditions of temperature and pressure with interesting conversions and selectivities despite the change of environment they underwent after their dissolution in water

Investigation of the surface chemistry of phosphine-stabilized ruthenium nanoparticles - an advanced solid-state NMR study

Gutmann, Torsten Bonnefille, Eric Breitzke, Hergen Debouttiere, Pierre-Jean Philippot, Karine Poteau, Romuald Buntkowsky, Gerd Chaudret, BrunoInternational audience31 P-13C REDOR NMR measurements allowed a reasonable approximation of distances between stabilizing ligands and carbon monoxide (CO) molecules on the surface of phosphine-stabilized ruthenium nanoparticles (RuNPs). The studied systems are RuNPs in the size range of 1-2 nm stabilized with 1,3,5-triaza-7-phosphaadamantane (PTA) or triphenylphosphine (PPh3) and exposed to a CO atmosphere. This study sheds some light on the interactions between CO and phosphine molecules as well as on their binding geometries on the surface of the RuNPs. As information on the ligand location and mobility is precious for the understanding of the chemical and catalytic properties of nanoparticles, these results support the interest of using sophisticated NMR tools to investigate their surface chemistry

Tin dioxide and noble metal nanostructures for olfactory gas detection

International audienceAir quality control in closed spaces (e.g. automotive cabin, transportation and offices or working places) is getting more and more relevant due to the actual pollution levels present in our environment. In the past, our research group has successfully developed an advanced generation of metal oxide gas sensor, based on the combination of a micromachined silicon substrates and nanosized core shell Sn/SnOx composite derived from organometallic synthesis [1]. These sensors have been industrialized and implemented as air quality sensors in the automotive industry. A very new and improved generation of integrated gas sensors is presented here. It combines an improved silicon micromachined substrate and a fully oxidized nanosized tin dioxide material [2-4]. A key parameter for an improved response of the sensor is the highly porous nature of the sensitive layer that leads to a high number of electrical contacts between oxide grains. Indeed, the higher is the number of possible current pathways during sensor operation, the lower is the risk of sensitivity decreases due to deactivation of grain boundaries. As a matter of fact, for a given volume of sensitive layer, nanopowders offer the best ratio of grains and grain boundaries. The presented results demonstrate the high thermomechanical properties of the silicon substrate, the electrical and thermal stability of the platinum based heater element, and the very low membrane deformation during operation. High quality and micron thick layers can be obtained with a very low defect level (no cracks, no délamination). In addition, our team has developed a catalysis oriented approach for the improvement of the sensor response and selectivity: noble metal (Ru, Pt...) are added to the SnO2 matrix in order to reduce the response time and to increase the sensitivity of the sensors. Gas responses under CO, C3H8, NH3 and CH3CHO on undoped and doped layer are presented and discussed in view of applications in the selective gas detection of odorous gases in automobile cabins