Gas sensing performance and charge-transfer mechanism of semiconducting single-walled carbon nanotubes

Large specific surface areas and unique monolayer atomic structures enable single-walled carbon nanotubes (SWCNTs) to exhibit highly local-environment-sensitive electrical properties, which have been demonstrated to be ideal candidates for the next-generation sensing nanodevices. However, the interfacial interaction between gas molecules and SWCNTs has not been investigated experimentally so far. Herein, (6, 5)-enriched semiconducting SWCNTs have been used to fabricate room-temperature gas sensors, which exhibits a high sensitivity of 232 % toward 1 ppm nitrogen dioxide (NO2) at room temperature. Importantly, the sensing mechanism has been first investigated according to the Raman shift of 2D peak in SWCNTs, which provides direct evidence for the interfacial charge transfer between NO2 molecules and SWCNTs. Moreover, an exponential relationship between the 2D peak position and NO2 concentration has been established, which can be used to simply evaluate the charge transfer and the adsorption state of gas molecules. We believe that our results will not only promote the development of high-performance SWCNT-based sensing devices, but also provide a novel methodology to characterize the interaction between gas/vapor molecules and carbon nanomaterials.