Amplified Quenching of a Conjugated Polyelectrolyte by Cyanine Dyes
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- 作者：Chunyan Tan ; Evrim Atas ; Jü ; rgen G. Mü ; ller ; Mauricio R. Pinto ; Valeria D. Kleiman ; and Kirk S. Schanze
- 刊名：Journal of the American Chemical Society
- 出版年：2004
- 出版时间：October 27, 2004
- 年：2004
- 卷：126
- 期：42
- 页码：13685 - 13694
- 全文大小：206K
- 年卷期：v.126,no.42(October 27, 2004)
- ISSN：1520-5126
文摘
The conjugated polyelectrolyte PPESO3 features a poly(phenylene ethynylene) backbonesubstituted with anionic 3-sulfonatopropyloxy groups. PPESO3 is quenched very efficiently (KSV > 106M-1) by cationic energy transfer quenchers in an amplified quenching process. In the present investigation,steady-state and picosecond time-resolved fluorescence spectroscopy are used to examine amplifiedquenching of PPESO3 by a series of cyanine dyes via singlet-singlet energy transfer. The goal of thiswork is to understand the mechanism of amplified quenching and to characterize important parametersthat govern the amplification process. Steady-state fluorescence quenching of PPESO3 by three cationicoxacarbocyanine dyes in methanol solution shows that the quenching efficiency does not correlate withthe Förster radius computed from spectral overlap of the PPESO3 fluorescence with the cyanines'absorption. The quenching efficiency is controlled by the stability of the polymer-dye association complex.When quenching studies are carried out in water where PPESO3 is aggregated, changes observed in theabsorption and fluorescence spectra of 1,1',3,3,3',3'-hexamethylindotricarbocyanine iodide (HMIDC) indicatethat the polymer templates the formation of a J-aggregate of the dye. The fluorescence dynamics in thePPESO3/HMIDC system were probed by time-resolved upconversion and the results show that PPESO3to HMIDC energy transfer occurs on two distinctive time scales. At low HMIDC concentration, the dynamicsare dominated by an energy transfer pathway with a time scale faster than 4 ps. With increasing HMIDCconcentration, an energy pathway with a time scale of 0.1-1 ns is active. The prompt pathway (
< 4 ps)is attributed to quenching of delocalized PPESO3 excitons created near the HMIDC association site, whereasthe slow phase is attributed to intra- and interchain exciton diffusion to the HMIDC.
< 4 ps)is attributed to quenching of delocalized PPESO3 excitons created near the HMIDC association site, whereasthe slow phase is attributed to intra- and interchain exciton diffusion to the HMIDC.