Magnetic edge state and dangling bond state of nanographene in activated carbon fibers

The electronic structure of nanographene in pristine and fluorinated activated carbon fibers (ACFs) have been investigated with near-edge x-ray absorption fine structure (NEXAFS) and compared with magnetic properties we reported on previously. In pristine ACFs in which magnetic properties are governed by nonbonding edge states of the pi electron, a prepeak assigned to the edge state was observed below the conduction electron pi* peak close to the Fermi level in NEXAFS. Via the fluorination of the ACFs, an extra peak, which was assigned to the sigma-dangling bond state, was observed between the prepeak of the edge state and the pi* peak in the NEXAFS profile. The intensities of the extra peak correlate closely with the spin concentration created upon fluorination. The combination of the NEXAFS and magnetic measurement results confirms the coexistence of the magnetic edge states of pi electrons and dangling bond states of sigma electrons on fluorinated nanographene sheets.