文摘
This study deals with the differentiation and quantification of both nitrogen dioxide and ozone at ppb level when using amperometric gas sensors. We investigate, here, the addition of a layer of MnO2 microparticles powder as a chemical filter for ozone in a commercial amperometric gas sensor. Experimental results show that a sensor equipped with an MnO2 powder filter is insensitive to O3 but gives a well-defined limited current signal when exposed to NO2. In contrast, an unfiltered sensor senses both gases with a defined sensitivity for each gas. We find that the use of a pair of sensors, with one of the sensors filtered and one unfiltered, allows the quantification of both O3 and NO2. However, the MnO2 filter confers some indirect NO cross-sensitivity to the filtered sensors. Further studies show that it is possible to minimize this unwanted cross-sensitivity by replacing the MnO2 microparticles powder filter by an MnO2/PTFE microparticle composite filter powder. We find that the developed sensors allow reproducible measurements, linear output with the concentration and significant O3 filter capacity for an extended period of time.
