Carbon nanotube networks as sensitive layers for resistive gas sensor applications

Abstract

Carbon nanotube (CNT) networks offer fascinating opportunities as active layers for gas sensor devices. We here review our work on the use of CNT fi lms prepared by airbrush spraying as sensitive layers in resistive sensor devices for gas detection. The sensor fi lms were fabricated by airbrushing nanotube dispersions on alumina substrates. Networks of different CNT materials were tested as active sensing element sensors for the detection of pollutant gases (H2, NO2, octane, toluene, NH3). Our results indicate that the CNT structure and chemical functionalization affect both the CNT entanglement within the airbrushed networks and their gas sensing performance. Thus, highly sensitive NO2 and H2 resistive sensors were fabricated out of networks of carboxylic acid functionalized double-walled carbon nanotubes and Pd-functionalized single-walled carbon nanotubes, respectively. Issues related to gas sensing mechanisms of the tested resistive sensors, and device performance dependence upon the sensor operation temperature are also discussed here. All tested resistive sensors provided negligible responses to interfering gases such as NH3, toluene and octane. CNT-based gas sensors made by other fi lm preparation techniques are also reviewed, and their gas sensor performance is compared to those reported here.