Fabrication and Characterization of Amino Group Functionalized Multiwall Carbon Nanotubes (MWCNT) Formaldehyde Gas Sensors

Multiwall carbon nanotubes (MWCNTs) formaldehyde gas sensors functionalized with amino group were fabricated on interdigitated electrodes and the effects of the amount of amino group functionalized, sensing layer thickness, operating temperature, and humidity on the sensors sensitivity were investigated. The MWCNTs sensors with the optimal amount of 18.19 wt% amino group functionalized showed superior sensitivity at the formaldehyde concentration as low as 20 ppb. The optimal operation temperature for the sensor was found to be 22 $^{\circ}{\rm C}$ , which is advantageous for real applications. The sensors sensitivity deteriorated with the increase of sensing layers thickness. The sensor with the sensing layer thickness of 8.1 $\mu{\rm m}$ was demonstrated to possess the optimal combination of sensitivity and reproducibility. The mechanisms by which the sensors sensitivity depended on the amount of amino group functionalized, sensitive layers thickness, operating temperature, and humidity were discussed.