Carbon nanotubes with adsorbed Au for sensing gas

In this paper, high-density carbon nanotube (CNT) are grown on an oxidized Si substrate by thermal chemical vapor deposition (CVD). CNT are 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 are ∼4.52 ?m and 45 nm, respectively. Au nanoparticles are coated onto nanotube surfaces to a thickness of ∼5 nm and the CNTs thus formed could be utilized to sense carbon dioxide (CO2), ethanol, and isopropyl alcohol vapor, respectively. In 800-ppm CO2 vapor at room temperature, the adsorption of Au nanoparticles increased the sensitivities of the device to these species from 1.9%, 1.7% and 1.5% to 3.4%, 3.3%, and 3.2%, respectively.