Graphene SOI CMOS sensors for detection of PPB levels of NO2 in air

There is considerable demand for sensors that are capable of detecting ultra-low concentrations (sub-PPM) of toxic gases in air. Of particular interest are NO₂ and CO that are exhaust products of internal combustion engines. Electrochemical (EC) sensors are widely used to detect these gases and offer the advantages of low power, good selectivity and temporal stability. However, EC sensors are large (~1 cm³), hand-made and thus expensive (~$25). Consequently, they are unsuitable for the low-cost automotive market that demands units for less than $10. One alternative technology is SnO₂ or WO₃ resistive gas sensors that are fabricated in volume today using screen-printed films on alumina substrates and operate at ~400°C. Unfortunately, they suffer from several disadvantages: power consumption is high ~200 mW; reproducibility of the sensing element is poor; and cross-sensitivity is high.