Poulsen Lars, Jazdzyk Mikael, Communal Jean-Edouard, Sancho-García Juan Carlos, Mura Andrea, Bongiovanni Giovanni, Beljonne David, Cornil Jérôme, Hanack Michael, Egelhaaf Hans-Joachim, Gierschner Johannes
Institute of Physical and Theoretical Chemistry, University of Tübingen, Auf der Morgenstelle 8, D-72076 Tübingen, Germany.
J Am Chem Soc. 2007 Jul 11;129(27):8585-93. doi: 10.1021/ja0714437. Epub 2007 Jun 12.
We present a combined experimental and theoretical study on energy transfer processes in a well-defined three-dimensional host-guest system, which allows for high chromophore concentrations while maintaining the highly luminescent properties of the molecules in solution. The self-assembled, nanostructured system with a defined ratio of included donor and acceptor molecules is amenable to quantitative comparison between experiment and theory. Experimentally, energy migration is monitored by steady-state and time-resolved fluorescence spectroscopy. From the theoretical side, the energy transfer process is modeled by a Monte Carlo approach including homo and hetero transfer steps with multi-acceptor distribution. In this dense system, the classical Förster point-dipole approach for energy transfer breaks down, and the hopping rates are therefore calculated on the basis of a quantum-chemical description of the donor and acceptor excited states. Thereby, the true directionality of the excitation diffusion is revealed. Excellent agreement with experimental donor and acceptor decays and overall transfer efficiencies is found. Even at low acceptor concentrations (down to 0.1%), efficient energy transfer over distances as large as 25 nm was observed due to rapid energy migration through a series of homo-transfer steps with preference along one direction of the structure.
我们展示了一项关于明确的三维主客体系统中能量转移过程的实验与理论相结合的研究，该系统允许高发色团浓度，同时保持分子在溶液中的高发光特性。具有确定比例的包含供体和受体分子的自组装纳米结构系统便于进行实验与理论之间的定量比较。实验上，通过稳态和时间分辨荧光光谱监测能量迁移。从理论方面，能量转移过程通过蒙特卡罗方法建模，包括具有多受体分布的同型和异型转移步骤。在这个密集系统中，经典的Förster点偶极能量转移方法失效，因此基于供体和受体激发态的量子化学描述计算跳跃速率。由此揭示了激发扩散的真实方向性。发现与实验供体和受体衰减以及整体转移效率具有极好的一致性。即使在低受体浓度（低至0.1%）下，由于通过一系列同型转移步骤且优先沿结构的一个方向进行快速能量迁移，也观察到了在长达25 nm的距离上的高效能量转移。
