Electrochemical Redox Switchable Dispersion of Single-Walled Carbon Nanotubes in Water

We present a new, efficient approach to achieve superior dispersibility of single-walled carbon nanotubes (SWNTs) in water by integrating reversible host-guest interaction and pi-pi stacking. In this approach, beta-cyclodextrin (beta-CD) was first modified with a pyrene group to be adsorbed onto the wall of pristine SWNTs via pi-pi stacking, followed by further functionalization with ferrocene (Fc)-terminated water-soluble poly (ethylene glycol) (PEG) through supramolecular host-guest interaction between beta-CD and Fc. Upon alternate electrochemical oxidative/reductive stimuli, the reversible host-guest pair enabled the PEG-Fc@Py-CD@SWNTs to exhibit switchable conversion between dispersion and aggregation states. Electric field controllable PEG-Fc@Py-CD@SWNTs with good reversibility and intact nanotube structure may find potential applications in selective screening of SWNTs, biosensors, and targeted drug delivery.