Abstract. A new method for the detection of nitric oxide (NO) in gas phase is based on a combination of acidic gas scrubbing, oxidation, and conductivity measurements using a chemically functionalized carbon nanotube field-effect transistor (NTFET) device. Gas mixtures containing NO are passed through an Ascarite scrubber and then an oxidizing material (CrO₃) which converts NO into NO₂. The latter is delivered to the surface of the NTFET sensor coated with poly(ethylene imine) (PEI) polymer. Interaction of the gas with a chemically functionalized NTFET results in a conductivity change that is proportional to the NO gas concentration. The wide range of NO gas concentrations from about 2 ppb up to 5 ppm was tested. A detection limit of NO has been measured as 5 ppb with a signal-to-noise ratio (S/N = 3) in inert atmosphere at a fixed relative humidity (RH =  30%). Cross-sensitivity to CO₂ and O₂ was measured in the gas mixture, modeling human breath conditions. Compared to using chemiluminescence, a state-of-the-art technique for monitoring NO concentrations, this method offers the advantages of low cost, compact size and simplicity of set-up for monitoring NO concentrations while overcoming the limitations of cross-contaminants, possibly creating a foundation for enabling self-diagnostics and home care for asthma sufferers.

Print publication: Issue 37 (19 September 2007)
Received 30 May 2007, in final form 26 June 2007
Published 22 August 2007