Oxidation of Graphene Nanoribbon by Molecular Oxygen

Density-functional theory based on first principles is used to investigate oxidation of a semiconducting graphene nanoribbon with armchair edges (9-AGNR) by oxygen. The calculated results demonstrate that the oxygen is favorably physisorbed on the inner of 9-AGNR, while the oxygen is chemisorbed at the edge of 9-AGNR. Compared to the oxygen chemisorbed (cyclo- addition) 9-AGNR, two epoxy groups formed from cyclo-additions at the edge of 9-AGNR is energetically preferred. It is also found that the uniaxial strain generated by the cooperative alignment of two epoxy groups can significantly change the band gaps of 9-AGNR, leading to a change in the band gap for 9-AGNR as the concentration of epoxy groups varies. The pronounced change in the electronic properties, in particular, the band gaps, of 9-AGNR, as oxygen is adsorbed on 9-AGNR, may indicate that a semiconducting AGNR could have a potential application as a chemical (oxygen) sensor.