Tube chirality

Figure 3. Calculated adsorption energies ads of a single hydrogen atom on the zigzag BNNTs (n,0) with n ranging from 5 to 10 versus the radius R of the tube. The heavy dots and triangles refer to the adsorption on the B atom and the N atom, respectively.The numbers in parenthesis stand for the tube chirality indices.The solid and dashed lines are intended as a guide to the eye.

Applications of CNTs based on their electrical properties strongly depend on the diameter and helicity as well as parity.2 3 Doping of CNTs by boron and nitrogen renders them p-type and retype, respectively. MWNTs and SWNTs doped with nitrogen 4 17 and boron"1 9 have been reported. Boron-doped carbon nanotubes appear to exhibit enhanced electron field emission due to the presence of the boron atom at the nanotube edges.20 2 N-doped CNTs show retype behavior regardless of tube chirality.22... 

Figure 3.12 Schematic representation of DNA wrapping around a CNT (inset) and an initial configuration of the C-oligomer wrapped along the (6,5) tube chirality. Carbon atoms of the CNT marked by light gray indicate the direction of DNA wrapping with seven cytosine bases per helical turn, which lay parallel to the tube surface and nearly normal to the tube chiral vector, thus increasing the n-jt overlap between the base and tube orbitals. Reprinted with permission from ref. 120. Copyright 2009 American Chemical Society.

Atomic structure of nanotubes can be described in terms of tube chirality, orhelicity, which is defined by the chiral vector, and the chiral angle, 0. Figure 9.17 shows visualized cutting a graphite sheet along the dotted lines and rolling the tube so that the tip of the chiral vector touches its tail. 

Depending on the tube chirality and diameter of the SWCNT, a single aryl group adsorption on metallic tubes is significantly stronger than that on semiconducting tubes, and the adsorption energy decreases with increased tube diameter. 

Maiti, A., Svizhenko, A., Anantram, M. (2002). Electronic transport through carbon nanotubes Effects of structural deformation and tube chirality. Physical Review Letters, 88,126805. 

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