Kuevda Alexey V, Espinoza Cangahuala Mónica K, Hildner Richard, Jansen Thomas L C, Pshenichnikov Maxim S
Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 3, 9747 AG Groningen, The Netherlands.
J Am Chem Soc. 2025 Feb 19;147(7):6171-6180. doi: 10.1021/jacs.4c17708. Epub 2025 Feb 4.
The initial stages of photosynthesis in light-harvesting antennae, driven by excitonic energy transport, have inspired the design of artificial light-harvesting complexes. Double-walled nanotubes (DWNTs) formed from the cyanine dye C8S3 provide a robust, self-assembled system that mimics natural chlorosomes in both structure and optical properties. Two competing molecular packing models─bricklayer (BL) and herringbone (HB)─have been proposed to explain the structural and optical characteristics of these DWNTs. This study resolves the debate by combining theoretical analysis with advanced polarization-resolved wide-field photoluminescence microscopy. Quantum-classical simulations reveal reduced linear dichroism (LDr) as a decisive parameter for distinguishing between the models. Experimental measurements of single DWNTs yielded LDr values as high as 0.93, strongly favoring the BL model. The BL model's unique excitonic patterns, dominated by negative couplings among individual chromophores, generate superradiant exciton states with transition dipoles preferentially aligned along the nanotube axis. In contrast, the HB model's mixed positive and negative couplings produce destructive interference, leading to a weaker alignment of transition dipoles. Our approach deepens the understanding of the structure-property relationships in self-assembled systems and demonstrates the potential of slip-stacking engineering to fine-tune excitonic properties for artificial light-harvesting applications.
由激子能量传输驱动的光捕获天线中的光合作用初始阶段，启发了人工光捕获复合物的设计。由花青染料C8S3形成的双壁纳米管（DWNTs）提供了一个强大的自组装系统，在结构和光学性质上都模拟了天然的叶绿体。已经提出了两种相互竞争的分子堆积模型——砖层（BL）模型和人字形（HB）模型——来解释这些DWNTs的结构和光学特性。本研究通过将理论分析与先进的偏振分辨宽场光致发光显微镜相结合，解决了这一争论。量子-经典模拟表明，降低的线性二色性（LDr）是区分这两种模型的决定性参数。对单个DWNTs的实验测量得出LDr值高达0.93，强烈支持BL模型。BL模型独特的激子模式，由单个发色团之间的负耦合主导，产生超辐射激子态，其跃迁偶极子优先沿纳米管轴排列。相比之下，HB模型的正负耦合混合产生相消干涉，导致跃迁偶极子的排列较弱。我们的方法加深了对自组装系统中结构-性质关系的理解，并展示了滑移堆积工程在微调人工光捕获应用的激子性质方面的潜力。
