Exciton-Exciton Annihilation as a Probe of Exciton Diffusion in Large Porphyrin Nanorings
Exciton-Exciton Annihilation as a Probe of Exciton Diffusion in Large Porphyrin Nanorings
复制标题
DOI：
10.1021/acs.jpcc.0c04546
复制
发表时间：
2020-08-27
影响因子：
3.7
通讯作者：
Meech, Stephen R.
中科院分区：
文献类型：
--
作者：
Bressan, Giovanni;Jirasek, Michael;Meech, Stephen R.
在过去的十年中，天然和人造环状超分子结构的光物理行为得到了深入研究。在人造结构中，大型全π共轭卟啉纳米环因其电子、结构和拓扑特征而特别令人感兴趣，这使得它们成为光捕获应用的合适候选者。许多因素影响此类结构收集和传输能量的效率。例如，在强烈的照射条件下，光捕获的效率可以通过竞争过程（例如激子-激子湮灭）来淬灭。在这里，我们研究了周长范围在 13 至 52 nm（10-40 卟啉单位）之间的一系列卟啉纳米环的瞬态吸收光谱的泵注量依赖性。这使得除了所研究的最小纳米环之外的所有纳米环中都可以分离出依赖注量的快速衰减成分。这种效应被归因于激子-激子湮灭，并适合一维激子扩散模型，该模型证实激子尺寸和/或其迁移率与纳米环尺寸成反比。
The photophysical behavior of natural and artificial cyclic supramolecular structures has been intensively investigated in the past decade. Among the artificial structures, large fully pi-conjugated porphyrin nanorings are of particular interest because of their electronic, structural, and topological features, which make them suitable candidates for light-harvesting applications. A number of factors affect the efficiency with which such structures harvest and transmit energy. For instance, under intense irradiation conditions, the efficiency of light harvesting can be quenched by competing processes, such as exciton-exciton annihilation. Here, we investigate the pump fluence dependence of the transient absorption spectra of a series of porphyrin nanorings ranging in circumference between 13 and 52 nm (10-40 porphyrin units). This allowed the isolation of a fluence-dependent fast-decaying component in all but the smallest nanorings studied. This effect has been assigned to exciton-exciton annihilation and fit to a one-dimensional exciton diffusion model, which confirms that the exciton size and/or its mobility are inversely proportional to the nanoring size.