posted on 2025-02-05, 01:30authored byAlexey
V. Kuevda, Mónica K. Espinoza Cangahuala, Richard Hildner, Thomas L. C. Jansen, Maxim S. Pshenichnikov
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 modelsbricklayer
(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.