The team reports that robust detection in a wide range of NO2 concentrations, 10-154 ppb, was achieved, highlighting the great potential for graphene-based NO2 sensors, with applications in environmental pollution monitoring, portable monitors, automotive and mobile sensors for a global real-time monitoring network.
The measurements were performed in a complex environment, combining NO2/synthetic air/water vapor, traces of other contaminants and variable temperature in an attempt to fully replicate the environmental conditions of a working sensor.
It was shown that the performance of the graphene-based sensor can be affected by co-adsorption of NO2 and water on the surface at low temperatures (≤70 °C). However, the sensitivity to NO2 increases significantly when the sensor operates at 150 °C and the cross-selectivity to water, sulphur dioxide and carbon monoxide is minimized. Additionally, it was demonstrated that single-layer graphene exhibits two times higher carrier concentration response upon exposure to NO2 than bilayer graphene.
The team stated that the potential for such miniature, high sensitivity and low cost sensors is huge for air quality measurements. At the moment the air quality is measured in specific locations using very expensive equipment. The future would be to distribute these low-cost sensors in large cities and therefore generate a dense monitoring network. The development and deployment of such highly sensitive and ultra-small footprint gas sensors is expected to have significant socio-economic impact by closely monitoring the air quality at the source, therefore enforcing environmental regulations aiming at improving the health and quality of life.