Determination of optimal nanotube radius for single-strand deoxyribonucleic acid encapsulation

The molecular interactions between a single-strand deoxyribonucleic acid (ssDNA) molecule and a carbon nanotube (CNT) are modelled to determine the suction force experienced by the DNA which is assumed to be located on the axis near the open end of a single-walled CNT (SWCNT). They determine the optimal nanotube radius for encapsulation, that is, the radius of the nanotube with the lowest interaction energy. The expression for the molecular interaction energy is derived from the 6-12 Lennard-Jones potential together with the continuum approach, which assumes that a discrete atomic structure can be replaced by a line or a surface with constant average atomic density. It was found that an ssDNA can be encapsulated inside a SWCNT with a radius larger than 8.2 Å, and it is shown that the optimal SWCNT needed to fully enclose the DNA molecule has a radius of 8.8 Å, which approximately corresponds to the chiral vector numbers (13, 13). This means that if it is wished to encapsulate the ssDNA into a CNT, an ideal SWCNT to do this is (13, 13) which has the required radius of 8.8 Å.