Overhauser shift and dynamic nuclear polarization on carbon fibers

We report on the first experimental magnetic resonance determination of the coupling between electrons and nuclear spins (1H, 13C) in carbon fibers. Our results strongly support the assumption that the electronic spins are delocalized on graphene like structures in the fiber. The coupling between these electrons and the nuclei of the lattice results in dynamic nuclear polarization of the nuclei (DNP), enabling very sensitive NMR experiments on these nuclear spins. For possible applications of graphene in spintronics devices the coupling between nuclei and electrons is essential. We were able to determine the interactions down to 30×10−9(30ppb). We were even able to detect the coupling of the electrons to 13C (in natural abundance). These experiments open the way for a range of new double resonance investigations with possible applications in the field of material science.