Electrophoretic deposition of Au NPs on MWCNT-based gas sensor for tailored gas detection with enhanced sensing properties

Multiwalled carbon nanotube (MWCNT)-based gas sensors were decorated by an electrophoretic deposition of electrochemically preformed gold nanoparticles (Au NPs) with controlled size and loading, for the detection of gaseous pollutants at sub-ppm concentrations and operating temperature in the range of 100-200 °C. The effects of the tailored Au content on the sensitivity and selectivity of MWCNT-based gas sensors were evaluated towards the NO2 monitoring, and also towards some interfering reducing gases, such as NH3 and H2S. Gas sensing measurement revealed the highest NO2 response up to sub-ppm level by using MWCNTs functionalized by the lowest Au content; instead, the worse NO2 response was obtained by modified MWNTs containing the highest Au loading. Moreover, the control of the deposited gold loading has allowed to control the MWCNT sensing response; specifically the increase of gold content on MWCNT has reduced the selectivity and sensitivity towards NO2 gas, and, on the contrary, at the same time it has improved those towards H2S and NH3 interfering gases. Finally, binary gas mixtures (NO2/H2S and NO2/NH3) were performed to evaluate the detection of the targeted NO2 gas, simulating possible real-world conditions.