1/9 - Faculty Candidate Seminar (chem bio): Dorthe Eisele, MIT
Center for Excitonics
Massachusetts Institute of Technology
Robust Excitons Inhabit Soft Supra-molecular Nanotubes
Nature's highly efficient light-harvesting antennae, like those found in Green Sulfur Bacteria, consist of supra-molecular building blocks that self-assemble into a hierarchy of close-packed structures. In an effort to mimic the fundamental processes that govern nature’s efficient systems, it is important to elucidate the role of each level of hierarchy: from molecule, to supra-molecular building block, to close-packed building blocks. Here, I will discuss the impact of hierarchical structure. I will present a model system that mirrors nature’s complexity: cylinders self-assembled from cyanine-dye molecules (as illustrated in the figure below). I will show that even though close-packing may alter the cylinders’ soft mesoscopic structure, robust delocalized excitons are retained: internal order and strong excitation-transfer interactions—prerequisites for efficient energy transport—are both maintained. These results suggest that the cylindrical geometry strongly favors robust excitons; it presents a rational design that is potentially key to Nature’s high efficiency, allowing construction of efficient light-harvesting devices even from soft supra-molecular materials.