Adsorption kinetics of NO 2 gas on oxyfluorinated graphene film.

We report the fabrication of high-performance NO ₂ gas sensors based on oxyfluorinated graphene (OFG) layers. At room temperature, the times of adsorption/desorption of NO ₂ on/from the surface of thin OFG films are less than 1200 s and can be reduced by increasing the operation temperature. The sensors are capable of detecting NO ₂ molecules at sub-ppm level with a sensitivity of 0.15 ppm ^-1 at 348 K. The temperature dependence of the rate constants shows that the simultaneous presence of a large number of fluorine- and oxygen-containing groups on the graphene surface provides the formation of low-energy sites (Δ H _a < 0.1 eV) for NO ₂ adsorption. The combination of the high sensitivity of the sensor and a reasonable adsorption/desorption time of the analyte is promising for on-line monitoring.