Carbon nanotube films for room temperature hydrogen sensing.

Thin, uniform, single-walled carbon nanotube films, made by a simple filtration process, subsequently coated with palladium, are shown to be promising detectors of hydrogen. The films detected hydrogen with relative responses of 20% at 100 ppm and 40% at 500 ppm concentrations. Most of the initial film conductance was recovered within 30 s by exposing the samples to air. This quick and easy recoverability make the Pd-coated nanotubes suitable for practical applications in room temperature hydrogen sensing while consuming only approximately 0.25 mW power. The film fabrication process provides highly reproducible control over the film thickness; an important ingredient for commercial production. In the course of this research strong evidence was obtained indicating that sputter deposition of metal onto the nanotubes, even under very low power, short exposure time conditions, does damage to the nanotubes.