Theory of DNA-wrapped Carbon Nanotubes

Carbon nanotubes embedded in single-stranded DNA (CNT@DNA) were investigated by self-consistent density-functional-based tight-binding calculations (DFTB). A phenomenological model for the stability was derived, which gives the CNT-DNA interaction energy as a function of the nanotube radii and the number of DNA chains. Single CNTs are readily complexed by the DNA, but for CNT bundles an essential energy gain is only obtained, if multiple chains wrap around the tubes. Hence, the destruction of the CNT bundles, e.g. by sonication, can promote the CNT@DNA complex formation. Pyrimidine-based homopolymeric DNA more effectively wraps the DNA, whereas purine-based DNA exhibits the larger radius selectivity. The CNT-DNA interaction is not a genuine Van-der-Waals’ interaction. In general, the electronic structure is close to the superposition of the DOS curves of the “free” DNA and CNT fragments, but the most strongly bonding systems are characterized by a number of the mixed electronic states below Fermi level. Hence, magic matching occurs in conjunction with remarkable charge transfer.