Excitation quenching in polyfluorene polymers bound to (6,5) single-wall carbon nanotubes

- Fluorescence of polymer train sections contacting SWNTs is quenched during 3 ps.
- Fluorescence of nonwrapped polymer tails is quenched during tens to hundreds of ps.
- PFO-BPy fluorescence quenching by SWNT occurs by energy rather than charge transfer.
- Aging of SWNT/PFO-BPy suspensions causes desorption of polymers from SWNT.

Fluorescence quenching of polyfluorene-based polymer (PFO-BPy) attached to single-wall carbon nanotubes (SWNT) has been investigated by means of fluorescence and transient absorption spectroscopy. Fluorescence of SWNT/PFO-BPy complex suspension in chlorobenzene decays nonexponentialy on a time scale from several to several hundreds of picoseconds, and experiences slower depolarization if compared with free polymer in solution. We attribute the slowly quenched and more polarized fluorescence to the polymer tail segments that are not in direct contact with the SWNT. Polymer fluorescence in SWNT/PFO-BPy solid films is quenched about 10 times faster than in suspensions. The initial excited state quenching in films occurs with a 2.3 ps time constant, which we attribute to the polymer chains intimately attached to the SWNT. Slow changes of the spectroscopic properties of the SWNT/PFO-BPy suspensions with time revealed that their aging is associated with the desorption of polymers from SWNT, increasing their tendency to aggregate.

85