Polyaniline/carbon nanotubes nanocomposite was synthesized by in situ polymerization. The samples were characterized by XRD, TEM, IR and EDS. The gas sensitivity properties of the sensors made from polyaniline/carbon nanotube nanocomposite were studied. The results showed that nanocomposite was composed of carbon nanotubes coated evenly by polyaniline, with a diameter of 60-80 nm. The gas sensitivity of polyaniline/carbon nanotube nanocomposite was higher than that of pure polyaniline. The sensor doped with 30 % mol carbon nanotubes has the highest gas sensitivity and highest selectivity for formaldehyde.
