Use of a voltammetric electronic tongue for predicting levels of nerve agent mimics

[EN] An electronic tongue (ET) based on pulse voltammetry containing a set of eight metallic electrodes (Au, Pt, Ir, Rh, Cu, Co, Ni and Ag) encapsulated on a stainless steel cylinder has been used to discriminate and predict levels of nerve agent mimics in aqueous environments. Analysis including principal component analysis (PCA) and partial least square techniques (PLS) have been applied for data management and prediction models. A good discrimination from other organophosphorous derivatives was found for the nerve agent simulants diethyl-chlorophosphate (DCP) and diethyl-cyanophosphate (DCNP).We thank the Ministerio de Ciencia y Tecnologia (project CTQ2006-15456-C04-01), and Universidad Politecnica de Valencia (project PAID-06-07-3243) for support. I.C. thanks the Universidad Politecnica de Valencia for a Doctoral Fellowship.S3253281

Template Free Synthesis of Hollow Ball-Like Nano-Fe2O3 and Its Application to the Detection of Dimethyl Methylphosphonate at Room Temperature

This paper is focused on the template-free synthesis of nanosized ferric oxide (nano-Fe2O3) and its application in quartz crystal microbalance (QCM) resonators to detect dimethyl methylphosphonate (DMMP), a simulant of Sarin. The X-ray diffraction (XRD) patterns confirm that the synthesized samples are made of Fe2O3 and the scanning electron microscopy (SEM) pictures show that the samples have ball-like shapes. The DMMP sensors with a sensing film of hollow ball-like and solid ball-like Fe2O3 are fabricated and their sensing characteristics are compared. The sensitivity of the hollow ball-like Fe2O3 sensor is more than 500% higher than the one of the solid ball-like Fe2O3 sensor. The hollow ball-like nano-Fe2O3 can be synthesized by a novel low temperature hydrothermal method. The sensors with the hollow ball-like Fe2O3 film perform well in a range of 1 to 6 ppm, with a sensitivity of 29 Hz/ppm at room temperature, while the appropriate recoverability and selectivity are maintained. In addition, the performance of different thicknesses of the sensing film of the hollow ball-like nano-Fe2O3 is investigated and the optimized relative film thickness of the hollow ball-like nano-Fe2O3 is found to be 20 μg/mm2

Study of a QCM Dimethyl Methylphosphonate Sensor Based on a ZnO-Modified Nanowire-Structured Manganese Dioxide Film

Sensitive, selective and fast detection of chemical warfare agents is necessary for anti-terrorism purposes. In our search for functional materials sensitive to dimethyl methylphosphonate (DMMP), a simulant of sarin and other toxic organophosphorus compounds, we found that zinc oxide (ZnO) modification potentially enhances the absorption of DMMP on a manganese dioxide (MnO2) surface. The adsorption behavior of DMMP was evaluated through the detection of tiny organophosphonate compounds with quartz crystal microbalance (QCM) sensors coated with ZnO-modified MnO2 nanofibers and pure MnO2 nanofibers. Experimental results indicated that the QCM sensor coated with ZnO-modified nanostructured MnO2 film exhibited much higher sensitivity and better selectivity in comparison with the one coated with pure MnO2 nanofiber film. Therefore, the DMMP sensor developed with this composite nanostructured material should possess excellent selectivity and reasonable sensitivity towards the tiny gaseous DMMP species

Semiconducting Metal Oxide Based Sensors for Selective Gas Pollutant Detection

A review of some papers published in the last fifty years that focus on the semiconducting metal oxide (SMO) based sensors for the selective and sensitive detection of various environmental pollutants is presented

Étude et réalisation d'amplificateur à transistor à effet de champ a l'AsGa refroidi à très basse température

Minimum noise figure and optimum source impedance of GaAs field-effect transistors cooled at cryogenic temperatures are computed. Noise characteristics are derived with excess of noise in low frequencies of the microwave band taken into account ; this low frequency noise nonnegligible at 300 MHz exceeds other sources of noise. Cooling influence was correlated to the physical changes of the material. Amplifiers using GaAs field-effect transistors (NE 244 and Gat 1) were designed at 300 MHz and cooled in liquide nitrogen and liquid helium. Noise performances of this amplifiers fits well with theory predictions. The liquid helium cooled amplifier using the transistor NE 244 has a noise figure of 0.25 dB.On calcule le facteur de bruit minimum et l'impédance de source optimale des transistors à effet de champ à l'AsGa refroidis à très basse température. Cette étude tient compte de l'excès de bruit dans les basses fréquences de la bande micro-onde que l'on ne peut négliger car par exemple à 300 MHz, il est plus important que les autres sources de bruit. On étudie l'influence du refroidissement sur les paramètres du transistor à partir des modifications des caractéristiques physiques du matériau semiconducteur. Des amplificateurs à 300 MHz utilisant des transistors à effet de champ à l'AsGa (NE 244 (1) et Gat 1 (2)) ont été réalisés et refroidis dans l'azote liquide et dans l'hélium liquide. Les caractéristiques du point de vue du bruit de ces amplificateurs correspondent aux prévisions théoriques. On a pu obtenir avec un amplificateur refroidi à l'hélium liquide utilisant un transistor NE 244 un facteur de bruit 0,25 dB

Tomographie axiale transverse d'absorption x en controles non destructifs

Différents aspects de l'application de la tomographie axiale transverse dans les Contrôles Non Destructifs industriels par rayons X et rayons gamma sont présentés. Nous montrons en particulier qu'un optimum de l'énergie du rayonnement à utiliser peut être trouvé. Cet optimum, qui dépend de l'objet lui-même, correspond à des processus d'interaction prépondérants qui peuvent être soit l'absorption photoélectrique, soit la diffusion Compton. Le choix de l'énergie a donc des conséquences importantes tant au niveau de l'acquisition qu'au niveau de l'interprétation. Certains problèmes statistiques de la reconstruction sont ensuite abordés, et un système d'étude, qui a été réalisé à l'E.T.C.A., est présenté

Shear-thinning fluids for gravity and anisotropy mitigation during soil remediation in the vadose zone

International audienc

Générateur d'impulsions pour un banc automatique de réflectométrie

National audienc