Doping-Dependent Energy Transfer from Conjugated Polyelectrolytes to (6,5) Single-Walled Carbon Nanotubes

Conjugated polymers exhibit strong interactions with single-walled carbon nanotubes (SWNTs). These enable the selective dispersion of specific semiconducting SWNTs in organic solvents and polymer-mediated energy transfer to the nanotubes followed by emission in the near-infrared. Conjugated polyelectrolytes with ionic side-chains can add further functionalities to these nanotube/polymer hybrids such as dispersibility in polar solvents (e.g., methanol) and self-doping. Here, we demonstrate and investigate energy transfer from a range of conjugated polymers to preselected (6,5) SWNTs with varying spectral overlap between the optical transitions of the polymer and nanotube. We find evidence for increased backbone planarization of the polymers wrapped around the nanotubes. Furthermore, ambient p-doping of hybrids of anionic conjugated polyelectrolytes and (6,5) SWNTs blocks energy transfer in contrast to cationic polyelectrolytes. By addition of a mild reducing agent, thus removing the p-doping, the energy transfer can be fully restored pointing toward an electron exchange mechanism. The p-doping of nanotube/polyelectrolyte hybrids in air and their doping-dependent emission and charge transport properties also become apparent in water-gated field-effect transistors based on such networks and might be useful for dual-signal sensing applications.