Intercalation and guest–host interaction in nano-graphite☆ Original Research Article

Nano-graphene having open edges has unconventional nanoscopic electronic and magnetic features inherited to the presence of non-bonding edge π-electron state appearing around the Fermi level. We investigate host–guest systems of nanographite in relation to their adsorption, doping and intercalation activities. Staging phenomenon is absent in nanographite intercalated with K, Br and I as expected for finite-size host–guest systems. The charge transfer is reduced/enhanced in donor/acceptor compounds in comparison with the corresponding bulk GICs. Iodine, which is not intercalated in bulk graphite, gives intercalated nanographite where the edge state plays an important role in the electronic structure. Fluorine prefers addition reaction with edge carbon atoms in the early stage of the reaction, which is followed by the fluorination in the interior sites, diminishing the edge state contribution to the electronic structure. Physisorption of guest molecules in the micropore space in the 3D nanographite network shows a magnetic switching phenomenon related to the edge-state spins. Edge state spins are a sensitive probe to gas adsorption, demonstrating a huge amount of helium condensation in the micropore space.