Étude d’une réaction des complexes dinucléaires de l’iridium Ir

La fixation du monoxyde de carbone sur les complexes conduit à la formation des complexes Ir2(µ-RC ≡ CR)(µ-S-t-C4H9)(µ-X)(CO)2(PPh3)2 (1a : R = CF3 ; X = CF3CO2. 1b : R = CH3CO2 ; X = CF3CO2. 1c : X = S-t-C4H9) ; R = CH3CO2) conduit à la formation des complexes Ir2(µ-RC ≡ CR)(µ-S-t-C4H9) (CO)3(X)(PPh3)2, 2a, b, c, dans lesquels le ligand X est passé de la position pontante à la position terminale, révélant par con séquent une inertie relative du pontage par l’alcyne. Les complexes 2 existent sous deux formes isomères α et β qui ont été isolées et caractérisées par spectroscopies IR, de RMN du proton, du phosphore et du carbone. Ces deux types d’isomères se différentient par les positions des ligands carbonyles et/ou du ligand X devenu ter minai par rapport au groupe S-t-C4H9 resté en position pontante. On a observé également à partir de 1c, la formation d’un composé que l’on peut identifier, sur la base de plusieurs arguments spectroscopiques, comme un troisième isomère présentant un motif -C(R) = C(R)-C(0)- en pont entre les deux atomes d’iridium. Il s’agit donc d’un cas d’insertion du groupement carbonyle dans une liaison métal-carbone du ligand acétylénique bimétallée

Room-Temperature Organometallic Synthesis of Soluble and Crystalline ZnO Nanoparticles of Controlled Size and Shape.

Nanomaterials made easy! The facile oxidation of [Zn(c-C6H 11)2] at room temperature in an organic solvent containing long-chain amine ligands leads to the formation of size- and shape-controlled crystalline ZnO nanoparticles (see picture). These particles, in the form of nanodisks and nanorods of low size dispersity in the 3-10 nm size range, are fully soluble in organic solvents (e.g., THF) and photoluminescent

EXAFS and XANES Study of a Pure and Pd Doped Novel Sn/SnOx Nanomaterial .

status: publishe

Improvement of micromachined SnO2 gas sensors selectivity by optimised dynamic temperature operating mode

International audienceThis study shows the influence of short temperature variations on the transient response of a nanoparticular SnO2 gas sensor. By consideration of the shape and time constants of the normalized response curves, we can differentiate different gas mixtures at a ppm level. In this paper, different concentrations of CO (from 50 to 200 ppm) are well differentiated even in high level of C3H8 and NO2 concentrations. The shapes of transient responses are also modified by adding different catalysts (Pt, Pd) in SnO2 sensing layer. This new method of analysis is promising to conceive a selective gas detector based on combination of temperature profiles and different sensitive layers

Optimised dynamic temperature operating mode specifically dedicated to micromachined SnO2 gas sensors

International audienceIn this paper, we show the influence of short temperature variations on the transient response of a SnO2 nanoparticular gas sensor. By consideration of the shape and time constants of the normalized response curves, we can differentiate different gasses mixtures at a ppm level. This new method of analysis is promising to conceive a gas detector based on combination of temperature profiles and different sensitive layers

Recherches récentes sur le cobalt carbonyle et ses dérivés

Faisant le point sur l'ensemble de leurs résultats obtenus au cours des dernières années, les auteurs développent divers aspects relatifs aux synthèses, à la physico-chimie et aux structures des complexes dérivés des cobalt carbonyle. L'étude concerne essentiellement : - les dérivés de simple substitution de l'octacarbonyle dicobalt et la tautomérie des complexes dinucléaires; - les dérivés mononucléaires ioniques et leur relation avec les formes alkyle et acétyle du cobalt (I); - le bis (tétracarbonyle cobalt) mercure et ses dérivés de substitution ; - les dérivés tétranucléaires et le phénomène de « migration intramoléculaire » des ligands. Les caractéristiques spectrographiques de quelque soixante-dix complexes sont fournies en annexe

Recherches récentes sur le cobalt carbonyle et ses dérivés Recent Studies of Cobalt Carbonyl and Its Derivatives

Faisant le point sur l'ensemble de leurs résultats obtenus au cours des dernières années, les auteurs développent divers aspects relatifs aux synthèses, à la physico-chimie et aux structures des complexes dérivés des cobalt carbonyle. L'étude concerne essentiellement : - les dérivés de simple substitution de l'octacarbonyle dicobalt et la tautomérie des complexes dinucléaires; - les dérivés mononucléaires ioniques et leur relation avec les formes alkyle et acétyle du cobalt (I); - le bis (tétracarbonyle cobalt) mercure et ses dérivés de substitution ; - les dérivés tétranucléaires et le phénomène de « migration intramoléculaire » des ligands. Les caractéristiques spectrographiques de quelque soixante-dix complexes sont fournies en annexe. <br> The authors review their findings concerning the synthesis, physico-chemical properties and structural nature of cobalt carbonyl derivatives. The article deals with : - Normal substitution of Col (CO),, and tautomerism of binuclear complexes; - lonic mononuclear derivatives in relation with alkyl and acetylcobaltcarbonyls ; - Bis (tetracarbonylcobalt) mercury and its substituted derivatives ; - Tetranuclear cobalt complexes exhibiting intramolecular scrambling. Spectrographic data of some 70 compounds are given

Influence of Humidity on the CO Sensitivity of a New Gas Sensor Based on SnO2 Nanoparticles Surface-Doped with Palladium and Platinum

International audienceIn this paper, we show the influence of two doping agents Palladium and Platinum on the sensitivity for CO sensing of the nanoparticular SnO2 sensors at an operating temperature of 450°C. It is well known that the evolution of the conductance of the sensitive layer is largely modified by doping. A study carried out to measure the influence of humidity demonstrates that if un-doped sensors show a variation of same sign but less important than in dry air, doped sensors display a very different behavior. Indeed, we obtain a point of null sensitivity between 0 and 10%RH (RH = relative humidity) and a strong inverse sensitivity above 15% RH. These results demonstrate the presence of unexpectedly different chemical operating modes for CO sensing according to the rate of humidity

A New Generation of SnO2 gas sensor for agro-industrial applications

International audienceA new generation of gas sensor which consists of a silicon platform with an integrated polysilicon resistor as heater and a nanoparticular SnO2 sensitive layer has been developed and characterized. Methods of deposition and oxidation of the sensitive layer on the substrate were first optimized. Then, a demonstrator was implemented to evaluate the sensor's electrical behaviour under controlled atmospheric conditions. An electrical circuit has been developed to model the electrical behaviour of the sensor. Comparisons between PSPICE simulations and experimental data shows close agreement

Characterization of Dynamic Measurements with Nanoparticular SnO 2 Gas Sensors

International audienceA temperature step dynamic measurement on a nanoparticular SnO2 gas sensor is studied.Different sequences applied on the heater sensor are investigated to determine the best way to have a reproducible response. The sensor performances are then compared for CO detection in isotherm mode and in dynamic mode, with the previously highlighted sequence.A characterization of the step length is also led to its influence on sensor sensitivity. Finally, the best temperature profile to use for dynamic measurements is presented to improve significantly sensor sensitivity, reproducibility and stability