LEAPS-MPS: Field-Driven Upconversion through Supramolecular Assemblies in Plasmonic Nanocavities

In this project, funded by the MPS-LEAPS (Launching Early-Career Academic Pathways) Program and managed by the Division of Chemistry (CHE), Professor Bangle and her students at North Carolina Agricultural & Technical State University will perform studies focused on the improvement of light harvesting for photocatalysis via upconversion. Photocatalysis uses light energy to drive desirable chemical reactions, but many such reactions require high energy blue and green light and waste low energy red and infrared light. Upconversion is a promising strategy to improve photocatalysis efficiency by combining two low-energy photons into one high-energy photon capable of activating photocatalysts. Professor Bangle and her students will improve the efficiency of upconversion by integrating upconverting supramolecular assemblies into nano-scale plasmonic cavities and engineering the light-matter interactions in the cavities to promote intermolecular energy transfer. Their studies could produce upconverting surfaces which use low energy light to drive reactions when integrated into a wide variety of existing photocatalytic systems. This research will introduce early-career undergraduate students to advanced training in chemical and physical experiments and encourage further scientific education. Professor Bangle and her students will use a combination of surface chemistry, chemical synthesis, nanofabrication, and ultrafast optical measurements to create bespoke nanocavities and supramolecular assemblies designed for controlled molecular orientations. Supramolecular assemblies will be formed from donor and acceptor molecules known to undergo upconversion via sensitized triplet-triplet annihilation. Professor Bangle and her students will build combined molecule-nanocavity systems which systematically control the orientation of molecular transition state dipoles and energy transfer vectors relative to electric fields in the nanocavity. They will further tune the resonance of the nanocavity relative to the absorption, emission, and energy transfer energies of the molecules and quantify the influence of field orientation and resonance energy on yields and kinetics of each photochemical process. This research will develop design rules for controlling photochemical outcomes in plasmonic nanocavities, produce ultrabright upconverted emission, and use this upconverted emission to drive green photocatalytic reactions with low energy and broadband light. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.