title: Fluorescence blinking, exciton dynamics, and energy transfer domains in single conjugated polymer chains.
abstract: In order to understand exciton migration and fluorescence intensity fluctuation mechanisms in conjugated polymer single molecules, we studied fluorescence decay dynamics at "on" and "off" fluorescence intensity levels with 20 ps time resolution using MEH-PPV [poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] dispersed in PMMA. Two types of intensity fluctuations were distinguished for single chains of conjugated polymers. Abrupt intensity fluctuations (blinking) were found to be always accompanied by corresponding changes in fluorescence lifetime. On the contrary, during "smooth" intensity fluctuations no lifetime change was observed. Time-resolved data in combination with data on fluorescence emission and excitation anisotropy lead to a picture where a single polymer molecule is seen as consisting of several energy transfer domains. Exciton migration is efficient within a domain and not efficient between domains. Each domain can have several emitting low-energy sites over which the exciton continuously migrates until it decays. Emission of individual domains is often highly polarized. Fluorescence from a domain can be strongly quenched by Forster energy transfer to a quencher (hole polaron) if the domain overlaps with the quenching sphere.
authors.affiliation: Chemical Physics, Lund University, Box 124, 22100 Lund, Sweden.
authors.forename: Hongzhen
authors.initials: H
authors.lastname: Lin
authors.forename: Seyed R
authors.initials: SR
authors.lastname: Tabaei
authors.forename: Daniel
authors.initials: D
authors.lastname: Thomsson
authors.forename: Oleg
authors.initials: O
authors.lastname: Mirzov
authors.forename: Per-Olof
authors.initials: PO
authors.lastname: Larsson
authors.forename: Ivan G
authors.initials: IG
authors.lastname: Scheblykin
mesh_terms: D004735:Energy Transfer; D005454:Fluorescence Polarization; D007700:Kinetics; D008856:Microscopy, Fluorescence; D008956:Models, Chemical; D011108:Polymers / Q000737:chemistry*; D019904:Polymethyl Methacrylate / Q000737:chemistry; D014753:Vinyl Compounds / Q000737:chemistry*
chemical_list: D011108:Polymers; D014753:Vinyl Compounds; C520682:poly(2-methoxy-5-(2'-ethylhexyloxy)-p-phenylenevinylene); D019904:Polymethyl Methacrylate