Ammonia gas sensors with Au-decorated carbon nanotubes

In this study, high-density carbon nanotubes (CNTs) are grown on an oxidized Si substrate by thermal chemical vapor deposition (CVD). CNTs were synthesized by thermal CVD at 700 °C in a C₂H₂ atmosphere and used to fabricate a gas sensing-device. The average length and diameter of the CNTs were about ~ 4.52 μm and ~ 45 nm, respectively. Au nanoparticles were coated onto nanotube surfaces to a thickness of approximately 5 nm and the CNTs thus formed could be utilized to sense acetone vapor. In 800 ppm ammonia (NH₃) vapor at room temperature, the adsorption of Au nanoparticles increased the sensitivities of the device to these species from 1.11, 1.54, 2.03, 2.44 and 2.74%, respectively.