Noncovalent interactions of derivatized pyrenes with metallic and semiconducting single-walled carbon nanotubes

Pyrene has been a popular molecular structure in the noncovalent functionalization of single-walled carbon nanotubes (SWNTs), and the selectivity between metallic and semiconducting SWNTs for the underlying interactions has been exploited for the postproduction metallic-semiconducting nanotube separation. Two pyrene derivatives, 1-pyreneacetic acid (PyAA) and 1-docosyloxylmethylpyrene (DomP), which are hydrophilic and hydrophobic, respectively, were evaluated on their noncovalent interactions with SWNTs, as relevant to their selectivity and applicability to the postproduction separation. The results suggested that the interactions were not only dependent on molecular structures but also sensitive to solvent conditions and that a relatively lower solvent strength environment (solutions of less polar solvents) might be more favorable to the realization of the selectivity between interactions with metallic and semiconducting SWNTs. The surprising differences for the two pyrene derivatives in terms of their doping effects on the band gap transitions in semiconducting SWNTs are also reported and discussed.