Long-range energy transport in single supramolecular nanofibres at room temperature

Abstract

Efficient transport of excitation energy over long distances is a key process in light-harvesting systems, as well as in molecular electronics. However, in synthetic disordered organic materials, the exciton diffusion length is typically only around 10 nanometres (refs 4, 5), or about 50 nanometres in exceptional cases, a distance that is largely determined by the probability laws of incoherent exciton hopping. Only for highly ordered organic systems has the transport of excitation energy over macroscopic distances been reported--for example, for triplet excitons in anthracene single crystals at room temperature, as well as along single polydiacetylene chains embedded in their monomer crystalline matrix at cryogenic temperatures (at 10 kelvin, or -263 degrees Celsius). For supramolecular nanostructures, uniaxial long-range transport has not been demonstrated at room temperature. Here we show that individual self-assembled nanofibres with molecular-scale diameter efficiently transport singlet excitons at ambient conditions over more than four micrometres, a distance that is limited only by the fibre length. Our data suggest that this remarkable long-range transport is predominantly coherent. Such coherent long-range transport is achieved by one-dimensional self-assembly of supramolecular building blocks, based on carbonyl-bridged triarylamines, into well defined H-type aggregates (in which individual monomers are aligned cofacially) with substantial electronic interactions. These findings may facilitate the development of organic nanophotonic devices and quantum information technology.

Exciton Dynamics in Phthalocyanine Molecular Crystals

“…4 Recent studies, however, have shown that an efficient singlet exciton migration can occur in highly ordered supramolecular materials. [6][7][8] In particular, Sung et al. have shown by ultrafast transient fluorescence spectroscopy that in helical π-stacks of perylene bisimides delocalized excitons are initially formed and move coherently along the chain in tens of femtoseconds prior to the excimer formation.…”

“…6 Haedler et al have demonstrated that one-dimensional self-assembled nanofibers, based on carbonylbridged triarylamine building blocks, are able to efficiently transport singlet excitons over more than 4 μm at room temperature by means of a predominantly coherent mechanism. 7 Heechul et al have obtained a tunable light-harvesting material, based on a selfassembled chromophore network controlled by a genetically-engineered virus template, which has exhibited enhanced exciton transport via a partially coherent regime. 8 These recent examples clearly highlight the growing interest for obtaining controllable molecular materials for potential nanophotonic and quantum information applications where excitons move beyond the incoherent transport regime.…”

Extended-Charge-Transfer Excitons in Crystalline Supramolecular Photocatalytic Scaffolds

“…Not only can nanostructure morphology be controlled through judicious molecular design, 4 but it is also well-established that chromophore arrays can facilitate manybody interactions, such as resonant energy transfer, making them attractive candidates for artificial photosynthesis. 5 However, the majority of photocatalysis investigations to date that involved organic chromophores were done with the molecules fully dissolved in solution. 6−8 In order to move forward with designing artificial systems based on chromophore arrays that can be considered photocatalytic materials, a detailed understanding of how intermolecular coupling modes and environmental effects impact their performance is required.…”

Effects of long-range hopping and interactions on quantum walks in ordered and disordered lattices

“…Quasi-particles with such tunnelling properties also arise in experiments probing excitonic energy transfer in molecular crystals [49], molecular aggregates [50], photo-sythetic complexes [51][52][53][54][55][56][57], artificial light-harvesting materials [58], and ensembles of Rydberg atoms [32,59]. The long-range tunnelling amplitudes are known to have a significant effect on the dynamical properties of quantum particles in lattice po-tentials [60][61][62][63][64][65][66]. In particular, the long-range tunnelling events may substantially decrease the mixing or hitting times of the corresponding quantum walkers.…”