Edge-functionalized graphene nanoflakes as selective gas sensors

• We exploit the potential applicability of using armchair graphene nanoflakes as gas sensor.
• Six different graphene nanoflakes including pristine, B- or N-doped as well as functionalized nanoflakes with COOH, CN, and NO2 have been investigated.
• Functionalization of graphene nanoflakes, particularly, by carboxylic functional group prompts both sensitivity and reactivity of the sheet toward NO.

Graphene nanoribbon has a great potential to be used in the future electronic applications. Working on desirable properties by modifying nanoribbons by appropriate elements or functional groups helps us find the suitable form of graphene nanoribbon for each application. The main goal of the present study is to exploit the potential applicability of using finite graphene fragments referred to graphene nanoflakes (GNFs) as gas sensor. For this purpose, the interactions between small gas molecules (O2, N2, CO and NO) and six different armchair GNFs including pristine, B- or N-doped as well as functionalized GNFs with COOH, CN, and NO2 have been investigated. We found that the pristine, B- and N-doped and also functionalized GNF are not sensitive to N2, O2 and CO. On the other hand, while the pristine GNF shows sensitivity and reactivity to NO molecule, functionalization of GNFs, particularly, by carboxylic functional group prompts both sensitivity and reactivity of the GNF toward NO. The strong interactions between the NO and the functionalized GNFs induce dramatic changes to GNF's electronic properties and lead to large opening of the band gap of the nanoflake. However, the results of this study open the ways to manipulate graphene nanoflakes and development of new and effective sensors based on functionalized nanoflakes.

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