Selective gas detection using a carbon nanotube sensor

A circular disk resonator is used to study the gas sensing properties of carbon nanotubes. It detects the presence of gases based on the change in the dielectric constant rather than electrical conductivity of single walled carbon nanotubes (SWNTs) upon gas exposure. A conducting circular disk is coated with electric arc prepared SWNTs and degassed by heating under a high vacuum. It exhibits noticeable shifts in resonant frequency to both polar $({\mathrm{NH}}_3$ and CO) and nonpolar gases (He, Ar, ${\mathrm{N}}_2,$ and ${\mathrm{O}}_2\mathrm{).}$ Gas concentrations as low as 100 ppm can be detected using this sensor configuration.