Remarkable improvement of CO-sensing performances in single-walled carbon nanotubes due to modification of the conducting channel by functionalization of Au nanoparticles

Recently, chemiresistor gas sensors based on carbon nanostructured materials such as single-walled carbon nanotubes (SWCNTs), multi-walled CNTs (MWCNTs), graphene, graphene oxide (GO), and reduced-graphene oxide (RGO) have been extensively studied for use in breath analyzers as well as industrial and environmental monitoring. In this study, in order to improve the CO gas sensing performance of networked SWCNTs, the surface of the SWCNTs was functionalized with Au nanoparticles (NPs) for application in highly sensitive and selective gas detection. The networked Au NP-functionalized SWCNTs were synthesized via a dipping method and self-agglomeration of the Au film. The responses of the Au NP-functionalized SWCNTs to various gases such as CO, NH3, C3H6O, C7H8, C6H6, NO2, and NO were investigated. The enhanced response to certain gases due to the presence of the Au NPs can be explained in terms of a synergic effect between catalytic and electronic sensitizations. In particular, the Au NP-functionalized SWCNT sensors are highly sensitive and selective to low ppm CO at room temperature. The detection limit of fabricated sensors for CO is as low as 1 ppm and good selectivity for 2 ppm CO is achieved for the first time.