Nanocrystalline ZnO quantum dot-based chemiresistive gas sensors: Improving sensing performance towards NO2 and H2S by optimizing operating temperature

Nanocrystalline ZnO quantum dots (QD) with a diameter of 10 nm was synthesized and tested toward eight different toxic industrial chemicals (i.e., nitrogen dioxide (NO2), hydrogen sulfide (H2S), ammonia (NH3), carbon monoxide (CO), methane (CH4), ethanol (C2H5OH), acetone (CH3)2CO, and toluene (C6H5CH3)) with a broad concentration range at five different operating temperatures. Systemic studies allow to determine the kinetics of gas sensing as well as the competing reactions of analytes with sensing material and adsorbed oxygen. ZnO QD showed an excellent sensing performance toward NO2 and H2S in comparison to other target analytes. The selectivity can be further improved by controlling the operating temperature (i.e., higher selectivity toward NO2 and H2S were achieved at 300 °C and 450 °C, respectively). Moreover, the optimal temperature was found to be analyte dependent.