Engineering couplings for exciton transport using synthetic DNA scaffolds

Abstract

Control over excitons enables electronic energy to be harnessed and transported for light harvesting and molecular electronics. Such control requires nanoscale precision over the molecular components. Natural light-harvesting systems achieve this precision through sophisticated protein machinery, which is challenging to replicate synthetically. Here, we introduce a DNA-based platform that spatially organizes cyanine chromophores to construct tunable excitonic systems. We synthesized DNA-chromophore nanostructures and characterized them with ensemble ultrafast and single-molecule spectroscopy and structure-based modeling. This synthetic approach facilitated independent control over the coupling among the chromophores and between the chromophores and the environment. We demonstrated that the coupling between the chromophores and the environment could enhance exciton transport efficiency, highlighting the key role of the environment in driving exciton dynamics. Control over excitons, as reported here, offers a path toward the development of designer nanophotonic devices. Excitons are the molecular scale currency of electronic energy. Control over excitons and their dynamics enables energy to be harnessed and directed for applications such as light harvesting and molecular electronics. The properties of the excitonic systems depend on intermolecular electrodynamic interactions within the material. In natural light harvesting these interactions are controlled through the precision of protein machinery, which is challenging to replicate synthetically. In this work, we design, build, and characterize synthetic excitonic systems composed of multiple chromophores scaffolded within DNA. By leveraging the nanoscale structural precision of DNA, we control multiple intermolecular interactions and demonstrate the ability of these interactions to enhance the efficiency of exciton transport. Excitonic systems in the condensed phase are controlled by electrodynamic couplings between the chromophores and between the chromophores and the surrounding environment. Here, we develop a DNA-based platform for excitonic systems with tunable couplings that we characterize using ultrafast multidimensional spectroscopy, single-molecule spectroscopy, and molecular dynamics simulations. Leveraging the tunability of this platform, we explore the role of the electrodynamic couplings in exciton transport.