Role of interface interactions in the sensitivity of sulfur-modified single-walled carbon nanotubes for nitrogen dioxide gas sensing

Single-walled carbon nanotubes (SWCNTs) possess the unique ability to tune their functional properties by modifying the outer surface or interior space. Using the same modifier – sulfur, we demonstrate a difference in sensing properties of coated and filled single-walled carbon nanotubes to gaseous nitrogen dioxide. A comprehensive investigation of materials by transmission electron microscopy, X-ray photoelectron spectroscopy, density functional theory, and kinetics simulation led to an in-depth understanding of the factors influencing the sensor response of sulfur-modified SWCNTs, such as the role of surface and volumetric processes and interface effects. The sulfur-filled nanotubes with sulfur coating showed an outstanding sensitivity to detect nitrogen dioxide over a range from 1 ppb to 10 ppm due to the involvement of sulfur species in charge transfer between nanotubes and adsorbed molecules. Our data create a platform for the development of sensitive and reversible gas sensors using nanotube-based networks.