Air pollution monitoring using tin-oxide-based microreactor systems

Recent research on metal-oxide gas sensors has shown that such devices respond to environmentally relevant concentrations of O3, NO2, NO and CO. Such sensors, therefore, hold the potential of becoming inexpensive monitors of air pollution. In our work, tin-oxide sensors were embedded into tiny microchambers with internal volumes of 270 μl to form microreaction chambers. Enclosing samples of polluted air within such chambers, gas depletion reactions can be observed, which provide analytical information about the pollutant species enclosed. We have extended this approach to a microanalysis system containing two sensor chambers, one equipped with a thin-film and the other with a thick-film tin-oxide sensor element. Performing experiments on such a system, we were able to obtain analytical information about air pollutants in relevant concentrations for indoor as well as outdoor applications. We further show that in addition to the very gas-analysis functions, our air-monitoring system can also be equipped with calibration and self-test features.