Gas sensors micro-array for air quality monitoring based on pure and doped SnO/sub 2/ thick sensing films

Among the many physical and chemical strategies used to make air pollution gas sensors for CO and NO ₂ monitoring, those employing multisensor arrays offer excellent selectivity, long lifetimes, low drift and low costs of manufacture. Targeting the two gases CO and N O ₂, new thick film sensor matrix was fabricated using the screen printing technology. With this purpose, undoped and noble metal-doped thick film SnO ₂ sensing layers deposited by screen printing technique upon micromachined Si substrate have been characterised. The main objective in this study has been the challenging perspective to define a sensing layer type which allows a high quality monitoring and easy discrimination of low concentration of NO ₂ by an interfering species like CO, both present in the outdoor air. The experimental results reported in this work have shown that combining the sensor technology with a suitable catalytic element in the present case, gold, palladium and platinum, low concentration of NO ₂ can be revealed with a sufficient selectivity towards CO.