  Electron spin resonance (ESR) investigation of graphene nanoribbons (GNRs)
prepared through longitudinal unzipping of multiwalled carbon nanotubes
(MWCNTs) indicates the presence of C-related dangling bond centers, exhibiting
paramagnetic features. ESR signal broadening from pristine or oxidized graphene
nanoribbons (OGNRs) is explained in terms of unresolved hyperfine structure,
and in the case of reduced GNRs (RGNRs), the broadening of ESR signal can be
due to enhancement in conductivity upon reduction. The spin dynamics observed
from ESR linewidth-temperature data reflect a variable range hopping (VRH)
mechanism through localized states, consistent with resistance-temperature
data.
