Promotional effect of the electron donating functional groups on the gas sensing properties of graphene nanofakes

The adsorptions of several gas molecules (O-2, N-2, CO, and NO) on functionalized graphene nanoflakes (GNFs) have been investigated. Three electron donating functional groups including -OH, -NH2 and -NHCHO are considered to improve the gas sensing behavior of GNF. The electronic properties of gas/GNF adducts are strongly dependent on the functional group and on the molecular adsorption configuration. Adsorption of NO molecule can significantly influence the electronic properties of functionalized GNFs, while adsorptions of O-2, N-2, and CO molecules have little effect. The most effective functional group is -NHCHO which has a prominent role in the enhancement of both sensitivity and reactivity of GNF toward NO. The strong interactions between NO and functionalized GNFs induce dramatic changes to the GNF's electronic properties and lead to large opening of the band gap. The introduced sensors also preserve their sensitivity under humid conditions. Our quantitative study on the impact of functionalization on the gas/GNF interaction has relevance for devising chemical modification strategies for designing selective carbon-based gas sensors.