Spectroscopy of Soft Matter, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany.
Macromolecular Chemistry and Bavarian Polymer Institute, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany.
J Am Chem Soc. 2020 May 6;142(18):8323-8330. doi: 10.1021/jacs.0c01392. Epub 2020 Apr 27.
Efficient long-range energy transport along supramolecular architectures of functional organic molecules is a key step in nature for converting sunlight into a useful form of energy. Understanding and manipulating these transport processes on a molecular and supramolecular scale is a long-standing goal. However, the realization of a well-defined system that allows for tuning morphology and electronic properties as well as for resolution of transport in space and time is challenging. Here we show how the excited-state energy landscape and thus the coherence characteristics of electronic excitations can be modified by the hierarchical level of H-type supramolecular architectures. We visualize, at room temperature, long-range incoherent transport of delocalized singlet excitons on pico- to nanosecond time scales in single supramolecular nanofibers and bundles of nanofibers. Increasing the degree of coherence, i.e., exciton delocalization, via supramolecular architectures enhances exciton diffusivities up to 1 order of magnitude. In particular, we find that single supramolecular nanofibers exhibit the highest diffusivities reported for H-aggregates so far.
高效的长程能量输运沿着功能有机分子的超分子结构是自然界将阳光转化为有用的能量形式的关键步骤。理解和控制这些在分子和超分子尺度上的输运过程是一个长期以来的目标。然而，实现一个能够调整形态和电子性质以及在空间和时间上解析输运的明确系统是具有挑战性的。在这里，我们展示了 H 型超分子结构的层次如何改变激发态能量景观，从而改变电子激发的相干特性。我们在室温下可视化了在皮秒到纳秒时间尺度上的单根超分子纳米纤维和纳米纤维束中离域单重态激子的长程非相干输运。通过超分子结构增加相干度，即激子离域度，激子扩散系数可提高一个数量级。特别是，我们发现单根超分子纳米纤维表现出迄今为止报道的 H 聚集体中最高的扩散系数。
