NMR chemical shifts of N-bearing graphene

Wang, X.*; Hou, Z.*; Ikeda, Takashi; Terakura, Kiyoyuki*

The NMR chemical shifts of possible N-containing moieties at edges and defects of graphene are investigated by using the first-principles method. Our computations show that pyridine-like and graphite-like N are rather easily identifiable using N NMR technique, in agreement with experiment. On the other hand, pyridinium-like N is hardly distinguished from pyrrole-like one because these N nuclei give nearly overlapping signals. However, our simulations suggest that H NMR is useful to discriminate between them; The NMR chemical shift of H directly bonded with pyridinium-like and pyrrole-like N is estimated as 0.8 and 10.8 ppm, respectively. The N NMR signals for various moieties at edges we considered are found to be similar to the corresponding ones at defects except for pyridine-like nitrogens. Conversely, the N NMR chemical shifts are altered sensitively by the degree of aggregation of pyridine-like N atoms both along armchair edges and at defect sites.