▎ 摘　　要

Electron spin resonance study of unzipped graphene nanoribbons (GNRs) reveals a specific carbon-related signal, denoted G(C), at g=2.0032, attributed to GNRs periphery centers. The signal is observed to be readily quenched upon O-2 adsorption, which appears to be fully reversible upon room temperature vacuum treatment. Its depassivation behavior, observed from 130 K onward, is well described by first-order kinetics, characterized by the dissociation energy of 0.58 +/- 0.04 eV of spread 0.11 +/- 0.02 eV. The G(C) signal is not sensitive to other gases, such as H-2, He, N-2, and Ar, pointing to a G(C)-O-2 physisorption interaction unique for GNRs, in agreement with theoretical insight. The G(C) center thus emerges as a highly selective, sensitive, and reversible O-2 sensor. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3559229]