Hole doping and surface functionalization of single-walled carbon nanotube chemiresistivesensors for ultrasensitive and highly selective organophosphor vapor detection

Abstract

We developed a chemiresistive sensor based on doped and functionalized semiconductingsingle-walled carbon nanotube (SWNT) networks for ultrasensitive and rapiddetection of dimethyl methylphosphonate (DMMP) (simulant of nerve agent sarin)vapor. The semiconducting SWNT network was deposited between interdigitatedelectrodes and modified by solid organic acid tetrafluorohydroquinone (TFQ).The TFQ molecules could not only selectively bind DMMP onto the sidewalls ofSWNTs via the strong hydrogen bonding interaction, but also tailor the electronicproperties of SWNTs via heavy hole doping. This synergetic effect significantlyimproved the sensitivity of the devices, and enabled the sensors to easily detectDMMP at 20 parts-per-trillion (ppt) concentration with a response time of less than2 min, without the need for pre-concentration of the analytes. This sensitivityis about five orders of magnitude higher than that of the unmodified SWNTchemiresistor, and also significantly higher than that of the functionalized SWNTchemiresistors previously reported. Moreover, the SWNT–TFQ sensors couldbe recovered when DMMP is replaced with referencing gas. The SWNT–TFQsensors also show excellent selectivity toward DMMP over some interfering organicvapors. The response mechanism, i.e. charge transfer and dedoping was investigated.