High-performance room-temperature formic acid vapor sensors based on multi-walled carbon nanotubes/polypyrrole composites

• MWCNTs/polypyrrole composites were prepared by in-situ polymerization with varying MWCNTs amounts. • 10–20 nm MWCNTs were found to be embedded on 50–200 nm polypyrrole particles. • Response to 1 vol% HCOOH at 25 °C was upsurged from 2.6 to 900 with 1 wt% MWCNTs. • The composite prepared with 1 wt% MWCNTs offered a low HCOOH detection limit of ∼0.1 vol% at 25 °C. • The sensor exhibited excellent HCOOH selectivity against H2, CO2, CH4, C2H5OH, CH3OH, and C3H6O. In this research, functionalized multi-walled carbon nanotubes/polypyrrole (fMWCNTs/PPy) composites were synthesized by in-situ oxidative polymerization approach to fabricate sensing films for room-temperature formic acid (HCOOH) detection. The material properties were characterized by X-ray spectroscopy, infrared spectroscopy, transmission electron microscopy, and nitrogen adsorption analysis. The study results confirmed the formation of well-defined multiwalled nanotubes embedded on PPy nanoparticulate matrix with varying MWCNTs loading levels. From gas-sensing measurement results, the addition of 1 %wt fMWCNTs during PPy polymerization greatly enhanced the sensor response from 2.6 to ∼900 towards 1 vol% HCOOH with excellent selectivity against H 2 , CO 2 , CH 4 , C 2 H 5 OH, CH 3 OH, and C 3 H 6 O at 25 °C. The dispersion of functionalized MWCNTs-PPy heterointerfaces could play an important role in the significant improvement of gas-sensing properties. Therefore, the functionalized MWCNTs-embedded PPy-based sensor would be an attractive choice for formic acid detection at room temperature and useful in medical and environmental applications. The formation of fMWCNTs/PPy heterointerfaces could play an important role in the significant improvement of gas-sensing properties via chemical and electronic mechanisms.