▎ 摘　　要

Purpose The authors designed those experiments to test the sensitivity of graphene when it is exposed to NO2 gas, to find a way to decrease the recovery time of graphene and to find the difference effect between monolayer and bilayer graphene in the experiments. Design/methodology/approach The authors transferred graphene from film on Cu foil to NO2 sensor sample and measured the resistances of on monolayer and bilayer graphene when they were exposed to NO2 gas under different concentration; then, the authors obtained the results. Findings The results show that monolayer graphene exhibits a linear response when the NO2 concentration is below 20 ppm. But the monolayer graphene will not be so sensitive to NO2 gas when the concentration continues to reduce. The desorption time of monolayer graphene is longer when compared with bilayer graphene. It shows faster recovery time and higher response of bilayer graphene under low NO2 concentration. And the limit detectable NO2 concentration of bilayer graphene is 50 ppb. Desorption time of bilayer graphene is shortened to below 20 s under UV light. Originality/value The authors found a reliable way to decrease the recovery time of graphene when it is exposed NO2 gas and got the concrete data.