Low-resistance gas sensors fabricated from multiwalled carbon nanotubes coated with a thin tin oxide layer

Gas sensors have been fabricated from multiwalled carbon nanotubes (MWNTs) coated with a thin tin oxide layer, and have been used to detect oxidizing and reducing gases down to a ppm level. The barriers between the tin oxide nanocrystal grains on the MWNTs dominate the sensor resistance in different gases, and the conducting carriers in the MWNTs have a low resistance, which make the resistance of the sensors much lower than that of SnO2 nanobelt sensors. The resistance is 130 kOmega in air, 230 kOmega in 2 ppm NO2, and 2.8 MOmega in 50 ppm NO2, so that impedance matching with amplifying circuits can be easily achieved. (C) 2004 American Institute of Physics.