Gas sensor using single-wall carbon nanohorns

We fabricated a gas sensor using single-walled carbon nanohorns (SWNHs) produced by the gas-injected arc-in-water method. This gas sensor consisted of agglomerated SWNHs as a coating film between Al electrodes on a glass substrate and the shift of the electric resistance of this coating film caused by gas adsorption was monitored. Its sensing property was examined for the detection of NH3 and O3 at room temperature. It was confirmed that the electrical resistance of the SWNHs film increases with adsorption of NH3, whereas the adsorption of O3 induced the decrease of the resistance. A model to correlate the gas concentration and the sensing property was proposed focusing on the detection of NH3 based on mono-layer adsorption and a second-order interaction of adsorbed gas molecules for charge transfer.