Transition metal and nitrogen doped carbon nanostructures

We review our theoretical first-principle studies of carbon nanostructures based on graphene sheets, carbon nanotubes, nanocones and fullerenes that are substitutionally doped with transition metal and nitrogen atoms. The results obtained show that metal doping leads to more stable systems in buckled rather than planar structures. The hybrid structures have low-lying excited states, allowing for catalytic activity, in analogy to metalloporphyrins and metallophthalocyanines, as confirmed in recent experiments with Fe-xN-doped carbon nanotubes. Metal-doped carbon nanocones and nanocapsules based on typical fullerenes manifest remarkable electronic and spin polarizations. Additional doping by boron atoms adjacent to the metals increases their HOMO-LUMO gap, stabilizes their electronic structures and causes that their ground states have higher spin multiplicity, where the spin density is spread over the systems. The metallic sites allow functionalization and potential activation of these nanosystems. The hybrid structures formed can have a broad range of applications in catalysis, molecular electronics, light-harvesting and nanomechanics. (C) 2009 Elsevier B.V. All rights reserved.