Abstract
The aim of this work is to investigate the gas sensing performance of single wall carbon nanotubes (SWCNTs)-based conductive sensors operating at low–medium temperatures (<250 °C). The investigated sensing films consists of an SWCNT network obtained by drop-casting a SWCNT suspension. Starting from this base preparation, different sensing devices were obtained by decorating the SWCNT network with materials suitable for enhancing the sensitivity toward the target gas. In particular, in this paper, nano-particles of gold and of TiO2 were used. In the paper, the performance of the different sensing devices, in terms of response time, sensitivity toward NO2 and cross-sensitivity to O2, CO and water vapor, were assessed and discussed. Sensors based on decorated SWCNT films showed high performance; in particular, the decoration with Au nano-particles allows for a large enhancement of sensitivity (reaching 10%/1 ppm at 240 °C) and a large reduction of response time. On the other hand, the addition of TiO2 nanoparticles leads to a satisfactory improvement of the sensitivity as well as a significant reduction of the response time at moderate temperatures (down to 200 °C). Finally, the suitability of using Au decorated SWCNTs-based sensors for room temperature sensing is demonstrated.
Highlights
Carbon nanotubes (CNTs), since their discovery in 1991 by Iijima [1], have deeply attracted the interest of researchers, enough to play a key role in nanotechnology nowadays [2,3,4,5], and have found employments in a wide range of engineering applications
single-walled carbon nanotubes (SWCNTs) consist of a single atom-thick layer of graphene wound on itself in a cylindrical shape, whereas multi-walled carbon nanotubes (MWCNTs) can be seen as multiple concentric SWCNTs structures
The analysis reported aims to characterize the dispersion of the SWCNTs prepared by the authors and the uniformity of the films by deposition
Summary
Carbon nanotubes (CNTs), since their discovery in 1991 by Iijima [1], have deeply attracted the interest of researchers, enough to play a key role in nanotechnology nowadays [2,3,4,5], and have found employments in a wide range of engineering applications. SWCNTs consist of a single atom-thick layer of graphene wound on itself in a cylindrical shape, whereas MWCNTs can be seen as multiple concentric SWCNTs structures. Their electronic behavior depends heavily on their size and chirality, CNTs can behave as semiconductors (with a band gap that can be modified as it depends, for instance, on the tube diameter) or, in some cases, exhibit a very large electrical conductivity and charge carrier mobility [2]. The research shows that CNTs with semiconductor behavior can be employed as gas sensing materials, exploiting the influence that the adsorption of gases from the environment has on their electronic conductivity. It was shown that adsorbates can donate or accept free carriers, they
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