(HCHO) by forming chemisorption. Besides, silicon is also used asdopant to enhance the gas sensing of graphene, mainly for sensingof NO and NO2 [12,13]. However, for doped-graphene the sensitivityis heavily limited by the low dopant concentration (2% [8,9,12,13] or3.12% [10] as reported) due to the fact that only the dopant providesreactive site for gas adsorption. Meanwhile, the doping concentration is also uncontrollable in experiments, making the sensingperformance unpredictable.