Internal doping of metallic carbon nanotubes for chemiresistive sensing of explosive molecules

Carbon nanotubes (CNTs) have been the focus of much chemical sensing research, typically employing a chemiresistive sensing mechanism. Their effective application in hazardous gas sensing has been hindered by a number of drawbacks, including: poor selectivity, irreversibility, temperature instability, and relatively high sensitivity to oxygen. All of these issues may be addressed by deploying metallic CNTs in a new configuration: nanotube sensor arrays internally doped by encapsulated species (halogens, alkali metals, interhalogens, and alkali metal halides) which p-dope or n-dope the pristine material. Such a sensor design offers: selectivity via the dissimilar response of the diversely doped tubes to various analytes, reversibility by establishing the fully cleaned CNT surface as a sensor reference state, temperature stability by encapsulation of the dopants, and doping-induced sensitivity to a range of analytes, including ammonia, nitrogen dioxide, and both nitramine and nitroaromatic explosives. Ab initio analysis suggests that internally doped metallic CNT sensor arrays can dramatically improve the performance of CNT based gas sensors, capitalizing on both the high mass specific surface area and the stable encapsulation features of one dimensional materials.