Energy transfer from photo-excited fluorene polymers to single-walled carbon nanotubes

The energy transfer from fluorene-based polymers such as poly(9, 9-dioctylfluoreny-2, 7-diyl) (PFO) and poly[(9, 9-dioctylfluorenyl-2, 7-diyl)-co-(bithiophene)] (F8T2) to single-walled carbon nanotubes (SWNTs) is proved by photoluminescence excitation (PLE) and fluorescence lifetime studies. The excitation wavelength to cause optimal emissions from SWNTs is tunable in a wide wavelength range from 388 to 480 nm (from 488 to 520 nm) depending on the concentration of excess PFO (F8T2) polymers. The energy transfer and hence the excitation wavelength to cause optimal SWNT emissions is govern by the chain conformation and aggregation state of the polymers proximate to SWNT surfaces. The PLE mapping technique, an ideal method to monitor the energy transfer process, is adopted to study the SWNT binding competition between PFO and F8T2. We conclude that SWNTs are preferentially bound with F8T2 polymers. Moreover, the molecular dynamic simulation also agrees well with the experiment results. This study explores the photon conversion process between aromatic polymers and SWNTs and suggests a convenient method of adjusting the desired wavelength for the optimal energy conversion, useful for polymer-SWNT composites in optoelectronic applications.