Titre : Fluorescence Behavior of Single Polyfluorene Nanoparticles.
Endroit : Pavillon Claire-McNicoll, salle Z-330 à 14 h.
Hôte : Professeure Julian Zhu.
Cette conférence sera prononcée par le professeur Shinjiro Machida du Département des sciences macromoléculaires et de génie au Kyoto Institute of Technology.
Résumé :
Conjugated polymers are expected to be applied to optoelectronic devices, such as light-emitting device and solar cell. The nanoparticles of the conjugated polymers are also studied as probes for bioimaging with lower toxicity compared to semiconductor quantum dots. Poly(9,9-di-n-octylfuluorenyl-2,7-diyl) (PFO) is one of the well-studied conjugated polymer showing bright fluorescence in the aggregated state. In particular, the PFO nanoparticles containing a crystalline phase (called β-phase) are reported to exhibit higher fluorescence quantum yield (0.40) than the nanoparticles of other conjugated polymers. For the imaging applications, it is important to reveal the photoluminescent characteristics of the conjugated polymer nanoparticles at the single particle level. In this study, we measured the time traces of the fluorescence intensity and the polarization degree of single PFO nanoparticles with different particle size and the degree of cristallinity. The prepared PFO nanoparticles containing β-phase showed stronger and red-shifted fluorescence compared to those in amorphous phase. According to Hambury-Brown and Twiss type photon correlation measurements, no photon antibunching was observed for the nanoparticles with sizes of 5-60nm, indicating that there are more than several emissive sites in a single PFO nanoparticle. In addition, discontinuous fluctuations were observed in both the emission intensity and the polarization degree of single nanoparticles. The amplitudes of such fluctuations werelarger for the nanoparticles with smaller size and higher crystallinity. These results indicated that these fluctuations were induced by the change in the emission quantum yield in each crystalline phase.
Références bibliographiques :
Wu, C.; Bull, B. Szymanski, C.; Christensen, K.; McNeill, J. ACS Nano, 2008, 2, 2415.
