Carbon nanotube-based SAW sensors

Surface acoustic wave (SAW) gas sensors based on the use of carbon nanotube (CNT) networks as sensitive layers have been investigated for the detection of atmospheric gas pollutants: volatile organic compounds (VOCs), NO
₂
, CO, and H
₂
. SAW sensor configuration consists of a delay line made on a piezoelectric substrate (ST -X cut quartz) and a sensitive layer (CNTs) deposited between the interdigital transducers (IDTs). CNT networks were fabricated by airbrushing single-walled-(SWCNTs) and double-walled- (DWCNTs) CNT dispersions onto quartz substrates. Among all the tested CNT materials and gases, only DWCNT -based SAW sensors were sensitive upon exposure to low concentration of octane and toluene, providing fast response and recovery times to these VOCs.