Plasma treatment as a way of increasing the selectivity of carbon nanotube networks for organic vapor sensing elements

Abstract

Multi-walled carbon nanotubes networks (MWCNTs) were used as a layer for organic vapor detection. The sensor detects volatile organic compounds (VOC). The gas sensing by MWCNTs is measured by means of macroscopic electrical resistance. The selected solvents had different polarities and volume fractions of saturated vapors. The electrical resistance of MWCNTs increases when exposed to organic solvent vapors, and a reversible reaction is observed when the MWCNT is removed from the vapors. The MWCNTs were modified by means of plasma treatment. For modifications RF plasma in O-2 at 50 Pa and an afterglow configuration were used. The modified MWCNTs show an increase in sensitivity caused by creating carboxylic groups on the surface of the carbon nanotubes. It leads, for example, to enhancement of the sensitivity from usual 30 % for heptane at RT to more than 200% after plasma treatment in O-2 for 10s.