Dispersion-Process Effects on the Photoluminescence Quantum Yields of Single-Walled Carbon Nanotubes Dispersed Using Aromatic Polymers

We studied the dispersion-process effects on the photoluminescence (PL) properties of single-walled carbon nanotubes (SWNTs) dispersed using poly[9,9-dioctylfluorenyl-2,7-diyl] (PFO) (PFO-SWNTs). The difference of the synthesis method (CoMoCAT, HiPco, and alcohol chemical vapor deposition) is insignificant for the PL quantum yields (QYs) of PFO-SWNTs. SWNTs processed using a moderate bath-type sonicator showed the maximum PL QY (similar to 2%) and the QY decreased drastically due to ultrasonic dispersion using a vigorous tip-type sonicator. The very low density of exciton quenching sites (<2 mu m(-1)) introduced by the vigorous sonication was deduced based on the exciton diffusion model, indicating that the nanotube length itself almost limits the PL QYs in PFO-SWNTs.