Single-walled carbon nanotube composite inks for printed gas sensors: enhanced detection of NO2, NH3, EtOH and acetone

The monitoring and detection of harmful vapours and precursor gases is an ever present concern to security services, industry and environmental groups. Recent advances in carbon nanotube based resistive sensors highlight potential applications in explosive detection, industrial and environmental monitoring. Metal oxide semiconducting (MOS) gas sensor technology also shows promise when applied in discriminatory arrays to form an electronic nose. Novel single-walled nanotube (SWNT)-metal oxide (SnO2 and WO3) composite inks were synthesised and used to fabricate sensors with enhanced responses to low concentrations of NO2, NH3, acetone and EtOH vapours. Characterisation of the sensing material was accomplished by X-ray diffraction (XRD), Raman spectroscopy, thermo-gravimetric analysis (TGA), UV-Vis-IR absorption spectroscopy (UV-Vis-IR), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The enhancements were found to depend on the preparation route and operating temperature of the devices. A micro-structural model of resistance contribution was applied to explain the improvements of up to 198% in sensor response. Modification of sensing characteristics, through incorporation of SWNTs produced by the high pressure carbon monoxide disproportionation (HiPco) process, provides a new route to improved sensitivity and selectivity in an array of SWNT modified devices, useful in trace gas detection.