On-board phthalocyanine gas sensor microsystem dedicated to the monitoring of oxidizing gases level in passenger compartments

The monitoring of in-vehicle pollutant concentrations by means of an on-board molecular semiconductor gas sensor microsystem is described in this paper. The main objective is to measure in real time with a high level of accuracy the variations of oxidizing gases concentration in bus passenger compartments to inform travelers or commuters and to evaluate the assessment of bus drivers’ exposure. A self-contained gas sensor microsystem of which the sensitive element is constituted by a thin layer of copper phthalocyanine has been developed, validated at laboratory under controlled experimental conditions and then implemented in a bus of the urban network of Clermont-Ferrand, France. Preliminary in-car measurements realized with commercial analyzers show that nitrogen dioxide is the major oxidizing gas present on urban roads and so is considered as the target gas in this study. Tests realized under artificially polluted atmosphere show the high performances obtained with our microsystem, such as high resolution, low threshold, good reproducibility, satisfying concentration range and real time detection. The calibration curve has been determined at laboratory by experiments made under low NO2 concentrations in the range of those measured in urban atmosphere. The relation between sensor microsystem response and gas concentration is established with accuracy. The validation of our microsystem is illustrated by measurements realized under real conditions, i.e., in an urban bus. It shows that NO2 concentration variations are mainly correlated with the nature of roads and that rates of pollutant measured in traffic are always greater than those measured by the nearest stations of the air quality control network.