Multi-wall carbon nanotube networks as potential resistive gas sensors for organic vapor detection

The sensitivity of multi-wall carbon nanotube (MWCNT) networks of randomly entangled pure nanotubes and those oxidized with acidic KMnO4 to various organic solvent vapors (iso-pentane, diethyl ether, acetone and methanol) has been investigated by resistance measurements. The solvents had different polarities given by Hansen solubility parameters and different volume fractions of saturated vapors defined by the vapor pressure. The results show that the network electrical resistance increases when exposed to organic solvent vapors, and a reversible reaction is observed when the network is removed from the vapors. The reaction with KMnO4 increases oxygen content on the nanotube surface and causes lower porosity of MWCNT network as well as higher electrical resistance, which improves the network selectivity to polar solvents. The investigated MWCNT networks could be potentially used as sensing elements for sensitive and selective organic vapor switches.