Real-time detection of organic acid gases by QCM sensor based on acidified MWCNTs/PANI nanocomposites

A quartz crystal microbalance (QCM) gas sensor, based on the acidified multi-walled carbon nanotubes/polyaniline (MWCNTs/PANI) nanocomposite, was developed to detect the organic acid gas in this study. The nanocomposite was obtained by direct polymerization of PANI on the surface of MWCNTs via in situ chemical oxidation and characterized morphologically and chemically by field emission scanning electron microscope, X-ray diffraction and Fourier transform infrared. The experimental results indicated that the MWCNTs/PANI modified QCM sensors had high sensitivity (38.51 Hz/(mg/m 3 ) for formic acid gas and 30.70 Hz/(mg/m 3 ) for acetic acid gas), excellent repeatability, reversibility, and long-term stability. The repeatability cycle tests of the sensor produced highly similar across the concentration gradients, achieving over 90% frequency recovery. Additionally, the putative adsorption mechanism on formic and acetic acid gas molecules could be mainly attributed to hydrogen bonding and plentiful active sites. This work indicated this acidified MWCNTs/PANI-based QCM gas sensor might represent a promising approach for real-time organic acid gas detection. Graphical abstract