The Physics & Astronomy Colloquium Series presents Dorthe M. Eisele of CUNY on “A Paradigm Shift Inspired by Nature: Overcoming Barriers to Functionalization of Supramolecular Assemblies for Solar Energy Harvesting Applications” on Friday, Feb. 5, at 4:10 p.m. at an Online Departmental Colloquium.
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Abstract: The future of sustainable energy technologies requires not only highly efficient but also robust light-harvesting (LH) materials, especially as rising global temperatures (increase of extreme weather events such as excessively high temperatures) threaten the efficiency of existing photovoltaic installations. Unlike current solar energy conversion technologies, natural photosynthetic organisms [1] have clearly evolved beyond these challenges, capturing and transporting solar energy both robustly and efficiently even under extreme environmental stress. In photosynthetic organisms, the first step (that is, light-harvesting) involves the interaction between light energy and the light-harvesting antenna, which are composed of delicate, weakly-bound structures known as supra-molecular assemblies (as illustrated in Figure-TOP). 
Delocalized Frenkel excitons—coherently shared excitations among molecular chromophores—are responsible for the remarkable efficiency of supramolecular light-harvesting assemblies within those photosynthetic organisms. However, the translation of nature’s successful design principles to applications in optoelectronic devices has been limited by the fragility of the supramolecular structures used and the delicate nature of Frenkel excitons. In my talk, I will present proof-of-concept that the intrinsic barriers towards functionalization of supramolecular assemblies can finally be overcome; through in situ cage-like scaffolding of individual supramolecular LH nanotubes [2], we designed highly stable supramolecular nanocomposites [3] with discretely tunable (~4.7-5.0 nm), uniform (±0.3 nm), cage-like scaffolds (as illustrated in Figure-BOTTOM). High-resolution cryo-TEM, spectroscopy, and near-field scanning optical microscopy (NSOM) revealed supramolecular excitons within cage-like scaffolds are robust, even under extreme heat-stress. Complementary substrate studies on prototype dye-sensitized solar cells showed that our nanocomposites’ precise scaffold tunability in-solution was also maintained upon immobilization onto a solid substrate. Together, these results indicate that our novel supramolecular nanocomposite system is a successful, critical first step towards the development of practical bio-inspired LH materials for solar-energy conversion technologies as well as a basis for future fundamental investigations that were previously not possible, such as dilution of supramolecular assemblies required for single-molecule imaging or precise tunability of scaffold dimensions for controlled functionalization of hybrid model systems, such as plexcitonic systems.
[1] Orf, G.S. and Blankenship, R.E., Photosynth. Res. 2013; Scholes, G.D., et al. Nature Chem. 2011; [2] Eisele et al., Nature Chem. 2012; Eisele et al., JACS 2010; Eisele et al., Nature Nanotech. 2009; Eisele et al., PNAS 2014 [3] Ng, K., Webster, M., Carbery W.P., Visaveliya, N., Gaikwad P., Jang, S., Kretzschmar, I., and Eisele, D.M., Nature Chem. (2020) 12, 1157 1164.
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