The paper presents the effect of acid treatment on the structure of single-walled carbon
nanotube (SWNT) bundles and on the characteristics of SWNT-based gas sensors. The commercial
SWNT powder was treated with a mixture of concentrated H2SO4:HNO3 (3:1 in volume) before used
to fabricate sensors for ammonia (NH3) detection at room temperature. The Transmission Electron
Microscopy (TEM) and Scanning Electron Microscopy (SEM) images indicated that the acid
treatment not only removed most of catalytic particles from the SWNT bundles, but also caused
SWNT bundles to be fragile. The fracture of the SWNT facilitated for gas molecules to adsorb in the
SWNT sites, leading to an enhancement in sensitivity of the sensors. Upon exposing to 50 ppm NH3
in 450 sccm of nitrogen flowing rate at room temperature, the resistance of the 2-h-stirred sensors
increased to 38% compared to 22% of the 1-h-stirred sensor. The recovery of the SWNT sensor was
also accelerated owing to the treatment. These findings opened a new direction to improve the
characteristics of SWNT-based gas sensors.
Enhancement of NH3 Gas Sensitivity at Room Temperature by Carbon Nanotube-Based Sensor Coated with Co Nanoparticles
