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Аннотация Heat-treatment-induced conversion of nanodiamond to nanographite is investigated. Graphitization starts at the surface region around a heat-treatment temperature of 900oC, then it proceeds inward in the particle, and finally it is completed around 1600oC, where nanographite particles form a polyhedron with a hollow inside. The change in the electronic feature is subjected to the structural change induced by the heat treat treatment. In the intermediate stage of graphitization, where graphene sheets are small and defective, charge transfer takes place from graphitic pi-band to non-bonding edge states. Electrophoretic deposition of nanodiamond particles provides technique of fabricating isolated single nanodiamond particles on a substrate. Successive heat-treatment at 1600oC converts a nanodiamond particle to a single nanographene sheet laying flat on a highly oriented pyrolytic graphite substrate. Weak interaction between the nanographene sheet and the substrate is expected to give a model system of nanographene, for which theory predicts the presence of nonbonding pi-electron states of the edge origin and its related unconventional nanomagnetism. This work is supported by the Grant-in-Aid for \glqq Research for the Future\grqq Program, Nano-Carbons and 15 105 005 from JSPS.