Mapping Forbidden Emission to Structure in Self-Assembled Organic Nanoparticles
Mapping Forbidden Emission to Structure in Self-Assembled Organic Nanoparticles
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DOI：
10.1021/jacs.8b09149
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发表时间：
2018-11-21
影响因子：
15
通讯作者：
Goldsmith, Randall H.
中科院分区：
文献类型：
--
作者：
Hinton, Daniel A.;Ng, James D.;Goldsmith, Randall H.
微观形貌与电子性能的相互作用是有机电子材料研究的一个重要课题。在这里，我们表明，螺芴官能化的硼-二吡咯亚甲基（BODIPY）与烷基乙酰基尾巴自组装成纳米粒子与定性不同的性能相比，聚合的物种。此外，纳米粒子表现出独特的发射性能，包括光致增亮，蓝色卫星峰，和光谱扩散主机。广泛的生物物理表征，包括单粒子成像和光谱，时间分辨荧光，再加上电子结构计算的基础上，实验确定的晶体结构，允许一个机制被开发。具体地，观察到BODIPY发色团形成准二维层，其中单位晶胞的堆叠根据堆叠的方向增加J-聚集体特征或H-聚集体特征。特别强的H耦合域显示了罕见的上激子态发射过程，违反了卡莎规则，并导致蓝色卫星峰。因此，结构的空间异质性映射到单粒子成像中看到的物理行为的梯度上，并且结构的时间演变映射到波动的发射行为上，如在单粒子光谱中看到的。总的来说，这个系统提供了一个物理结构和电子性质如何交织在一起的惊人例子，以及一个难得的机会来使用一个图表。
The interplay between micromorphology and electronic properties is an important theme in organic electronic materials. Here, we show that a spirofluorene-functionalized boron-dipyrromethene (BODIPY) with an alkyl norbornyl tail self-assembles into nanoparticles with qualitatively different properties as compared to the polymerized species. Further, the nanoparticles exhibit a host of unique emissive properties, including photobrightening, a blue satellite peak, and spectral diffusion. Extensive photophysical characterization, including single-particle imaging and spectroscopy, and time-resolved fluorescence, coupled with electronic structure calculations based on an experimentally determined crystal structure, allow a mechanism to be developed. Specifically, BODIPY chromophores are observed to form quasi-two-dimensional layers, where stacking of unit cells adds either J-aggregate character or H-aggregate character depending on the direction of the stacking. Particularly strongly H-coupled domains show the rare process of emission from an upper exciton state, in violation of Kasha's rule, and result in the blue satellite peak. The spatial heterogeneity of structure thus maps onto a gradient of photophysical behavior as seen in single-particle imaging, and the temporal evolution of structure maps onto fluctuating emissive behavior, as seen in single-particle spectroscopy. Taken together, this system provides a striking example of how physical structure and electronic properties are intertwined, and a rare opportunity to use one to chart the other.