Twist Angle Plays an Important Role in Photophysical Properties of a Donor-Acceptor-Type Conjugated Polymer: A Combined Ensemble and Single-Molecule Study
Twist Angle Plays an Important Role in Photophysical Properties of a Donor-Acceptor-Type Conjugated Polymer: A Combined Ensemble and Single-Molecule Study
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DOI：
10.1021/jp209405k
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发表时间：
2011-12-15
影响因子：
3.3
通讯作者：
Vacha, Martin
中科院分区：
文献类型：
--
作者：
Habuchi, Satoshi;Fujita, Hiroyuki;Vacha, Martin
我们通过系综和单分子光谱以及密度泛函理论（DFT）计算研究了供体受体型共轭聚合物的光物理性质。该聚合物基于炔连接的 1,8-咔唑 (Cz) 并拥有苯并噻二唑 (BT) 作为电子受体部分。与模型化合物的比较表明二聚体结构是聚合物的光谱单元。单分子双色激发荧光和荧光寿命实验表明，聚合物分子呈现出较宽的荧光强度比和荧光寿命分布。结合 DFT 计算，我们证明了 Cz 和 BT 部分之间的扭转角在决定聚合物的光谱特性方面发挥着核心作用。单分子荧光光谱测量进一步支持了这一结果。光谱测量还表明单链内的片段间相互作用。此外，单分子散焦和偏振荧光成像表明在单个聚合物链内发生了有效的激子迁移和捕获。这些实验还揭示了单个聚合物分子内最低能量位点的变化。
We investigated photophysical properties of a donor acceptor-type conjugated polymer by means of ensemble and single-molecule spectroscopy as well as density functional theory (DFT) calculation. The polymer is based on an alkyne-linked 1,8-carbazole (Cz) and possesses a benzothiadiazole (BT) as an electron acceptor moiety. A comparison with model compounds demonstrated that the dimer structure is the spectroscopic unit of the polymer. Single-molecule two-color excitation fluorescence and fluorescence lifetime experiments showed that the polymer molecules displayed broad distributions of fluorescence intensity ratio and fluorescence lifetime. Together with the DFT calculation, we demonstrated that the twist angle between the Cz and BT moieties played a central role in deciding those spectroscopic properties of the polymer. This result was further supported by single molecule fluorescence spectral measurement The spectral measurement also suggested intersegment interactions within the single chains. Furthermore, single molecule defocused and polarization fluorescence imaging suggested efficient exciton migration and trapping occurring within the single polymer chain. These experiments also revealed changes of the lowest energy site within the single polymer molecules.