The Role of Exciton Hopping and Direct Energy Transfer in the Efficient Quenching of Conjugated Polyelectrolytes

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• 作者：Jü ; rgen G. Mü ; ller ; Evrim Atas ; Chunyan Tan ; Kirk S. Schanze ; and Valeria D. Kleiman
• 刊名：Journal of the American Chemical Society
• 出版年：2006
• 出版时间：March 29, 2006
• 年：2006
• 卷：128
• 期：12
• 页码：4007 - 4016
• 全文大小：262K
• 年卷期：v.128,no.12(March 29, 2006)
• ISSN：1520-5126

文摘

The dynamics of fluorescence quenching of a conjugated polyelectrolyte by a cyanine dye areinvestigated by femtosecond fluorescence up-conversion and polarization resolved transient absorption.The data are analyzed with a model based on the random walk of the exciton within the polymer chain anda long-range direct energy transfer between polymer and dye. We find that rapid intrachain energy migrationtoward complex sites with the dye leads to the highly efficient energy transfer, whereas the contributionfrom direct, long-range energy transfer is negligible. We determine the actual density of complexes withthe dye along the polymer chain. A clear deviation from calculations based on a constant complex associationconstant is found and explained by a reduced effective polymer concentration due to aggregation. Altogether,the quenching efficiency is found to be limited by (i) the energetic disorder within the polymer chain and (ii)the formation of loose polymer aggregates.