Eric Pasquinet

Metalloporphyrins as sensing material for quartz-crystal microbalance nitroaromatics sensors

Five octaethylporphyrins (OEP) and tetraphenylporphyrins (TPP): (OEP)InCl, (OEP)MnCl, (OEP)GaCl, (TPP)Pd, and (TPP)RhI have been deposited as sensitive coating onto quartz-crystal microbalances. The sensitivities of the resulting sensors have been measured with respect to 2,4-dinitrotrifluoromethoxybenzene vapors. When exposed to the nitroaromatic compound, a large and significative response is recorded for every tested porphyrin, the detection process being slightly reversible. Along with a good sensitivity, the sensors exhibit an excellent selectivity when common solvents are used as interfering vapors. Among all the studied derivatives, (OEP)MnCl appears as the most sensitive and selective coating.

Comparison of fluorescence and QCM technologies: Example of explosives detection with a π-conjugated thin film

A pi-conjugated compound was synthesized as a sensitive material for explosives detection. The detection of vapors of 2,4-dinitrotoluene was demonstrated with quartz crystal microbalance (QCM) and fluorescence transduction methods. The fluorescence intensity monitoring shows a higher sensitivity and selectivity than the monitoring of the QCM frequency. Both methods appear to be synergic when used simultaneously as the sensor helps to discriminate interferent vapors from nitroaromatics.

Ability of various materials to detect explosive vapors by fluorescent technologies: A comparative study ☆

For the development of fluorescent sensors, one of the key points is choosing the sensitive material. In this article, we aim at evaluating, under strictly identical experimental conditions, the performance of three materials for the detection of dinitrotoluene (a volatile marker of trinitrotoluene) through different parameters: response time, fluorescence intensity, sensitivity, reversibility, reaction after successive exposures and long-term stability. The results are discussed according to the nature of the sensitive materials. This first study rendered it possible to select a conjugated molecule as the best sensitive material for the development of a lab-made prototype. In a second part, the selectivity of this particular sensitive material was studied and its ability to detect TNT could be demonstrated.

Efficient Sensing of Explosives by Using Fluorescent Nonporous Films of Oligophenyleneethynylene Derivatives Thanks to Optimal Structure Orientation and Exciton Migration

The fluorescence of thin films of a diimine-substituted phenyleneethynylene compound can be efficiently quenched by nitroaromatic vapors, which is not the case for the unsubstituted parent compound. Thin-film porosity is usually considered to be an essential factor for efficient quenching, but in the present case the origin of the quenching is completely different, as both films are nonporous and hermetic to 2,4-dinitrotoluene (DNT) molecules. The molecular organization in the two crystallized thin films offers a low level of πu2005stacking for both compounds, but the orientation of the phenylenethynylene fluorophore differs markedly with respect to the surface of the films. For the substituted compound, the fluorophore is almost parallel to the surface, thus making it readily available to molecules of a nitroaromatic quencher. This rationale is also observed in the case of a related compound bearing methoxy side chains instead of the long octyloxy moieties. Fluorescence-lifetime experiments show that the efficient quenching process in the nonporous crystallized films of the substituted compound is due to a fast (<70u2005ps) diffusion of excitons from the bulk of the film toward the surface where they are quenched, thus providing evidence of antenna effects.