Highly sensitive and selective NO2 detection by Pt nanoparticles-decorated single-walled carbon nanotubes and the underlying sensing mechanism

In this study, we have demonstrated highly sensitive and selective NO2 gas sensors based on single-walled carbon nanotubes (SWCNTs) decorated with Pt nanoparticles (NPs) by applying a sputtering technique and sequential thermal treatment under atmosphere. The effect of the operating temperature on the sensing capabilities of SWCNT sensors was determined by using NO2 as a representative oxidizing gas. In spite of higher NO2-response of SWCNT sensors at 100°C than that at room temperature (25°C), their sensing characteristics for all gases such as NO2, NO, C6H6, C7H8, C3H6O, CO, and NH3, respectively, were investigated at room temperature for actual sensing applications. In order to estimate the NO2-selectivity of Pt NPs-decorated SWCNT sensors, the cross-sensibilities of the fabricated sensors to 2ppm target gases were measured at room temperature. The sensing results revealed that sputtering and post-annealing techniques were an effective means of decorating SWCNT surfaces with catalytic Pt NPs; the significant improvement in NO2-detection (i.e., response and selectivity for NO2) of SWCNT sensors, owing to this decoration, was also confirmed. The methodology used in this study can pave the way for synthesizing various combinations of metal NPs and carbon-based nanostructured materials, which may be used as sensing materials for detecting hazardous gas species.