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Communication Dans Un Congrès Année : 2008

An original all-organic sensor with integrated gas filtering layer for selective measurements of NO2

Résumé

The selective and real time monitoring of oxidising gases in atmosphere by semiconductor gas sensors remains a real challenge despite all improvements to reach analyzer performances. Thanks to its insensitivity to reducing species and its high reactivity with oxidising ones, even for low concentrations, copper phthalocyanine (CuPc) is one of the most attractive semiconductor for this application. In recent works, we have shown that selective detection of O3 can be obtained with CuPc based gas sensor, using an appropriate methodology of measurements exploiting the fastest kinetics of response to this gas [1-2]. For the selective detection of NO2 in air, ozone constitutes the most important interfering agent and leads to the irreversible degradation of phthalocyanine molecular units in long term which reduces the sensors lifetime [3]. Thus, to efficient monitoring of NO2 in atmosphere by phthalocyanine gas sensors, it appears necessary to eliminate O3 without altering NO2 concentration, by means of selective filter. Among all the material investigated as ozone filter (MnO2 powder or impregnated grids, charcoal, C60 powder, stainless steel cuttings, indigo powder...), only indigo can be considered as a real selective ozone filter. Moreover, indigo powder being easily sublimed to be deposited as thin layers, this material is really suitable for the realization of integrated selective ozone filter. The structure investigated in this work is constituted by a 300nm-CuPc thin film as sensitive layer and an additional indigo evaporated film as the filter layer. The range of thickness investigated for indigo layer is 10-100nm. The very low intrinsic conductivity of indigo films (Σ = 2.10-107-1.cm-1) makes them insulating, that's avoid bypassing the sensitive layer. Sensor responses measured for the same concentration of NO2 and O3 emphasize that response and recovery times remain high, gas/phthalocyanine interactions are reversible, the response under O3 is negligible and kinetics of response to NO2 is slower than device without indigo filter due probably to the slow diffusion of NO2 species through the filtering layer to reach the sensitive one. The last point is confirmed by experiments made on structures with different thicknesses of indigo: the thicker the layer is, the slower the kinetics of response is. The integrated indigo layer on phthalocyanine sensors makes them selective to NO2 and avoids the fast ageing effect due to the strong and irreversible interaction of O3 on the sensitive layer.
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Dates et versions

hal-00282838 , version 1 (28-05-2008)

Identifiants

  • HAL Id : hal-00282838 , version 1

Citer

Jérôme Brunet, Bernard Lauron, Alain Pauly, Christelle Varenne, Marcel Bouvet, et al.. An original all-organic sensor with integrated gas filtering layer for selective measurements of NO2. 12th International Conference on ORGANIZED MOLECULAR FILMS (LB-12), Jul 2007, Cracovie, Poland. ⟨hal-00282838⟩
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