Gas sensing at the nanoscale: engineering SWCNT-ITO nano-heterojunctions for the selective detection of NH₃ and NO₂ target molecules

Abstract

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.

Highly Conductive Copper Selenide Nanocrystal Thin Films for Advanced Electronics

“…According to the positive response of the chemiresistors, we suggest that the major sensing mechanism for our NC arrays is the induced expansion of the interparticle spacing upon exposure to both polar and nonpolar analytes, which leads to an increase in resistance. Even though the observed magnitude of the relative response of our films is lower than that in some reports in the literature, − one should note that the films investigated here have a very small thickness (2–3 monolayers), show a fast response and recovery within the seconds time regime, respond nearly rectangularly, and operate at room temperature and under ambient conditions. They were also prepared by a room-temperature technique without any further thermal treatment.…”

Electronically Coupled, Two-Dimensional Assembly of Cu1.1S Nanodiscs for Selective Vapor Sensing Applications

“…In comparison with other previously reported chemiresistors based on NC ensembles for room temperature vapor sensing, these preliminary sensing measurements are encouraging. For instance, networks of Au NCs cross-linked with a variety of alkanethiols have shown Δ R / R 0 -values between 0.1 and 10% but suffer from gradual degradation in air due to oxidation of the thiol cross-linkers. ,,− Utilizing more durable tin-doped indium oxide NCs yielded Δ R / R 0 -values of 2–3%. , Higher values of 80–500% are typically only obtained for very large analyte concentrations or at elevated temperatures (300 °C). , For example, ZnO nanoflowers decorated with Au NCs have been reported to exhibit a Δ R / R 0 of 7500% toward 100 ppm acetone, however only at a working temperature of 270 °C . The material investigated in the present paper is operative under ambient conditions, unoptimized and holds the potential for selective vapor sensing at low detection limits due to its heterostructure as outlined above.…”

Facile Fabrication of Hybrid Carbon Nanotube Sensors by Laser Direct Transfer

“…The slope (0.00164) was obtained from the calibration curve of the sensor response in Figure 5c. For the LIFT-printed SWCNT@SnO 2 sensors, we obtained a LOD = 23.93 ppt, which is among the lowest LOD value reported by other chemiresistive sensors based on hybrid carbon nanotubes and tin oxide nanoparticles [27]. Even more, this LOD is two orders of magnitude lower than the LOD of a single tin oxide nanowire [28].…”