▎ 摘　　要

We show that graphene films synthesized by chemical-vapor-deposition enables detection of trace amounts of nitrogen dioxide (NO2) and ammonia (NH3) in air at room temperature and atmospheric pressure. The gas species are detected by monitoring changes in electrical resistance of the graphene film due to gas adsorption. The sensor response time was inversely proportional to the gas concentration. Heating the film expelled chemisorbed molecules from the graphene surface enabling reversible operation. The detection limits of similar to 100 parts-per-billion (ppb) for NO2 and similar to 500 ppb for NH3 obtained using our device are markedly superior to commercially available NO2 and NH3 detectors. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4720074]