Realisation of highly sensitive and selective NO2 detection at room temperature utilizing defect-induced single-walled carbon nanotubes combined with Pt functionalisation

Abstract

For the discriminative detection of trace amounts of certain gas molecules in ambient environments, the gas response, selectivity, and humidity independence of sensing characteristics should be improved to realise real-time environmental monitoring applications. In this study, we implement a NO2 gas sensor operating at room temperature with excellent selectivity. The fabricated sensor exhibits good NO2 response even under a humid atmosphere between 33% and 76% RH (RH = relative humidity), compared with previously reported carbon-based sensing materials. To synthesise Pt-functionalised defect-induced single-walled carbon nanotubes (SWCNTs), pure SWCNTs are heat treated at 700 °C for 1 h under an Ar atmosphere for defect formation; subsequently, nanosized Pt particles are randomly functionalised on the surfaces of defect-induced SWCNTs via optimal ultraviolet irradiation. The Pt-functionalised defect-induced SWCNTs achieves high NO2 response, low detection limit (67 ppb), strong selectivity, good reversibility, and the ability to detect NO2 under a humid atmosphere. However, they exhibit only moderately improved humidity-immune NO2 sensing characteristics. The NO2 response of both the Pt-functionalised and defect-induced SWCNTs deteriorates significantly in a humid atmosphere (76% RH). These results show that Pt-functionalised defect-induced SWCNTs are a promising sensing material for the detection of NO2 gas in real-time applications.