Gas sensing at the nanoscale: engineering SWCNT-ITO nano-heterojunctions for the selective detection of NH and NO target molecules.

The gas response of single-wall carbon nanotubes (SWCNT) functionalized with indium tin oxide (ITO) nanoparticles (NP) has been studied at room temperature and an enhanced sensitivity to ammonia and nitrogen dioxide is demonstrated. The higher sensitivity in the functionalized sample is related to the creation of nano-heterojunctions at the interface between SWCNT bundles and ITO NP. Furthermore, the different response of the two devices upon NO exposure provides a way to enhance also the selectivity. This behavior is rationalized by considering a gas sensing mechanism based on the build-up of space-charge layers at the junctions. Finally, full recovery of the signal after exposure to NO is achieved by UV irradiation for the functionalized sample, where the ITO NP can play a role to hinder the poisoning effects on SWCNT due to NO chemisorption.