Supramolecular Surface Modification and Solubilization of Single-Walled Carbon Nanotubes with Cyclodextrin Complexation

A novel approach to solubilize single-walled carbon nanotubes (SWCNTs) in the aqueous phase is described by employing supramolecular surface modification. We use cyclodextrin complexes of synthetic molecules that contain a planar pyrene moiety or a bent, shape-fitted triptycene moiety as a binding group connected through a spacer to an adamantane moiety that is accommodated in the cyclodextrin cavity. The binding groups attach to the sidewalls of SWCNTs through a pi-pi stacking interaction to yield a supramolecular system that allows the SWCNTs to dissolve in the aqueous phase through the formed hydrophilic cyclodextrin shell. The black aqueous SWCNT solutions obtained are stable over a period of months. They are characterized through absorbance, static, and time-resolved fluorescence spectroscopy as well as Raman spectroscopy, TEM, and fluorescence-decay measurements. Furthermore, the shape-fitted triptycene-based system shows a pronounced selectivity for SWCNTs with a diameter of 1.0 nm.