Nanoparticles-based chemical gas sensors for outdoor air quality monitoring microstations

Current cost-effective semiconductor sensors used to monitor indoor air quality are not suitable for outdoor air quality monitoring due to their insufficient sensitivity and to their cross-sensitivity to humidity. We present here some of our consolidated results on the optimization of chemical gas sensors based on metal oxide semiconductors. In order to increase sensitivity and selectivity while keeping fabrication at low cost, three major research directions have been considered: (1) the use of semiconductor nanoparticles in the fabrication of screen-printed gas sensors to increase the sensitivity; (2) the printing of sensitive layers on alumina tiles using a simple mechanical layer-by-layer technique to further increase the sensitivity; (3) the control and tailoring of surface chemistry of nanoparticles proved to be a critical step for further device optimisation. To date, our sensor prototypes are capable of detecting O3 and NOx concentrations down to 20 and 50 ppb, respectively, and CO concentrations down to 3 ppm in air. These prototype devices can be used as sensing elements in novel and cost-effective air monitoring microstations.