The electronic structures and properties of open-ended and capped carbon nanoneedles

The existence of a family of very thin carbon needlelike nanostructures is predicted: the geometry and stability of several carbon nanoneedles (CNNs) formed by C4 and C6 units have been studied by quantum chemistry computational modeling methods. The structures of carbon nanoneedles are tighter than even the smallest single wall nanotubes (SWNTs) based on (4, 0) naphthacene. The electronic properties, energetic stability of geometrical structures with various terminal units are investigated. The relatively large band gaps, the strong bonding, and additional orbital interactions within the C4 rings and between the C4 layers make the H4(C4)(n)H4 type molecules nonmetallic. We have found indications that if the CNN (3, 0) structures are very long (in the limit of infinite-length), then they are likely to have semiconducting properties and could possibly be used as actual semiconductors. The studied families of CNNs can be considered as carbon nanostructures with unique structural and chemical properties and with possible potential for unusual electronic properties, with likely practical applications as nanomaterials and nanostructure devices.