Highly Sensitive Detection of NO2 by Au and TiO2 Nanoparticles Decorated SWCNTs Sensors

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 TiO 2 were used. In the paper, the performance of the different sensing devices, in terms of response time, sensitivity toward NO 2 and cross-sensitivity to O 2 , 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 TiO 2 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.

NO2 Sensing with SWCNT Decorated by Nanoparticles in Temperature Pulsed Mode: Modeling and Characterization

“…The sensing films, as well as the sensors’ structure, used in this work were realized according to the procedure described in detail in Reference [ 3 ]. For completeness and clarity, a brief summary is reported here.…”

“…Details about the measurement and characterization system used to acquire the sensor responses, as well as the used sensor structure, can be found in References [ 22 , 23 , 24 ], and a schematic representation is reported in Figure 1 . It is worth to notice that a deeper investigation concerning the performance of the proposed sensing devices, in terms of response time, cross-sensitivity to different target gases and humidity levels, was presented and discussed by the authors in Reference [ 3 ]. The system remotely manages and controls the working conditions in the gas measurement chamber in terms of gas concentration and species, keeping the total gas flow constant during measurements thanks to a digitally controlled gas flow meter system (BronkHorst F-201C).…”

“…In fact, it is well known that these materials act as catalysts and favor the adsorption of the target gas. For example, it was shown that SWCNT decorated with both TiO 2 and Au become more active at a lower temperature with respect to the pristine material [ 3 ].…”

“…The suitability of single-wall carbon nanotubes (SWCNT)-based materials as sensing layers for toxic gas detection has been widely investigated in the last years [ 1 , 2 , 3 , 4 , 5 ], and recent researches have shown that they can be successfully employed to realize conductive gas sensors with promising performance. The achieved results point out the potentialities of these materials, but a large effort is still needed to reach the exhaustive knowledge of their gas sensing properties [ 6 ], which is needed to enable the evolution of commercial solutions employing SWCNT-based sensors.…”

Special Issue “Advanced Nanomaterials Based Gas Sensors”

“…Both metal and metal oxide NPs have been used for this purpose. Among the contributions to this Special Issue, the use of Au and TiO 2 NPs is studied in [4], in which successive drop-casting of colloids containing the SWCNTs and the NP over a pair of electrodes was used to obtain the decorated nanotubes. This facile procedure of decoration allowed for increased sensitivity to NO 2 with reduced response and recovery times while retaining a low response to humidity.…”