Joining Nanotubes with Pentagons and Heptagons

The different images show either different orientations of the tube or have the pentagons and heptagons marked in colour to make them easier to spot. Click on an image to see a larger version..

"It is possible to connect two nanotubes with different chiralities by just introducing a pair of heptagon and pentagon in the otherwise perfect hexagonal graphite lattice. Quasi one-dimensional heterojunctions can therefore be realized in this way, including metal-semiconductor hybrids for which interesting properties may be expected."

(9,0)-(5-5) knee The (9,0)-(5,5) knee illustrated here connects a nanotube with the parallel orientation (bottom) to one with the perpendicular orientation (top). The diameters of the two half nanotubes are close to 0.35 nm.
(10,0)-(6,6) knee The (10,0)-(6,6) knee is a semiconductor-metal hybdrid. The calculations indicate that the band gap requires a distance of the order of 1 nm to settle in the semiconducing nanotube.
(8,0)-(7,1) knee A group in Berkley University has investigated the electronic properties of small-bend heterostructures in which the pentagon and heptagon are adjacent. Local densities of states were computed by Green's functions for several systems, including the (8,0)-(7,1) hybrid illustrated on the left (by courtesy of Leonor Chico). The lower half of this hybrid is a semiconductor, the upper part is a metallic chiral nanotube.
(9,0)-(12,0) connection The (11,0)-(12,0) connection is a semiconductor-metal hybrid. Two nanotubes with the parallel (or zig-zag) orientation are connected with a pair of edge-sharing pentagon (red) and heptagon (blue) oriented parallel to the tubule axis. This results in a straight connection.

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