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

Abstract

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 ${\mathrm{SnO}}_2$ nanobelt sensors. The resistance is $130\mathrm{k}\Omega$ in air, $230\mathrm{k}\Omega$ in $2\mathrm{ppm}$ ${\mathrm{NO}}_2$ , and $2.8\mathrm{M}\Omega$ in $50\mathrm{ppm}$ ${\mathrm{NO}}_2$ , so that impedance matching with amplifying circuits can be easily achieved.