How strain controls electronic linewidth in single beta-phase polyfluorene nanowires.
Low-temperature single-molecule fluorescence spectroscopy reveals pure, virtually defect-free chains of the one-dimensional crystalline beta-phase of polyfluorene. The likelihood of beta-phase formation is shown to correlate directly with the initial shape of the polymer chain, with extended chains preferentially forming this planarized phase. Planarized chains, characterized by a distinct spectroscopic signature can, however, exhibit substantial bending within the plane. This bending results in a strong increase in the elementary transition linewidth of the conjugated segment. The transition linewidth provides a lower limit to the electronic dephasing time of the excited state of >3 ps at 5 K. Remarkably, bending does not appear to disrupt the pi-electron conjugation so that the emission from a single bent beta-phase chromophore is not necessarily linearly polarized as is generally assumed.
Da Como
Enrico
E
Photonics and Optoelectronics Group, Department of Physics and CeNS, Ludwig-Maximilians-Universität, Amalienstrasse 54, D-80799 Munich, Germany. Enrico.Dacomo@physick.uni-muenchen.de
Becker
Klaus
K
Feldmann
Jochen
J
Lupton
John M
JM
D003460:Crystallization / Q000379:methods*; D004548:Elasticity; D004559:Electric Wiring; D004579:Electron Transport; D005449:Fluorenes / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D036103:Nanotechnology / Q000379:methods*; D043942:Nanotubes / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D044367:Phase Transition; D011108:Polymers / Q000737:chemistry*; D013314:Stress, Mechanical; D013499:Surface Properties
D005449:Fluorenes; D046911:Macromolecular Substances; D011108:Polymers