Controlling Energy Distribution Pathways in Designer Photocatalysts for Efficient Polymer Synthesis

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With the support of the Chemical Catalysis program in the Division of Chemistry, Zachariah A. Page and Sean T. Roberts of The University of Texas at Austin are studying how the chemical structure of visible and near-infrared light absorbing dye molecules influences their ability to catalyze the additive manufacturing of plastics in an energy-efficient manner. Traditional light-based manufacturing relies on the use of dyes that operate only with high-energy ultraviolet (UV) light. This reliance on UV light is both energy-intensive and limits the functionality of materials that can be produced due to the low penetration depth of UV light and its potential to induce photodamage. The funded research teams aim to overcome this limitation by synthesizing new dye molecules comprised of earth-abundant elements and examining the ability of these so-called 'photocatalysts' to efficiently harvest the energy contained in visible/near-infrared (IR) light to power chemical reactions. These fundamental efforts are anticipated to increase the accessibility of light-based manufacturing at an affordable price, which has direct implications in technologies such as coatings, microelectronics, and 3D printing. The broader impacts of the project will extend to providing new training opportunities for both undergraduate and graduate students in interdisciplinary chemistry with activities ranging from chemical synthesis to laser-based spectroscopic characterization. Moreover, Page and Roberts will bridge educational programs at UT Austin and Austin Community College to create a channel for students to share knowledge and interact via hands-on research opportunities in an effort to improve diversity in STEM (science, technology, engineering and mathematics).Under this award, the UT-Austin collaborative team of Page and Roberts has as its overarching goal the development of eco-conscious photocatalysts that can harvest low-energy, visible-to-near infrared light with efficiency and selectivity that extend beyond our current capabilities with UV light, the industrial gold standard. To this end, three aims will be addressed. The first involves the establishment of a quantitative correlation between the structure of heavy-atom free photocatalysts (e.g., those without toxic halogens or expensive metals) and their ability to induce polymerization via long-lived spin-triplet states. The second aim is to identify individual dyes capable of absorbing multiple different colors of light and using that distinct, dual-band absorptive property to drive orthogonal chemical transformations (i.e., wavelength-selective catalysis). The third aim seeks to drive rapid photopolymerizations in UV-opaque materials by converting more transparent low energy visible/near-infrared photons into high-energy ones via triplet fusion-based photon upconversion. Each aim combines the synthesis of novel dye molecules with ultrafast spectroscopic characterization to create a closed-loop of knowledge with the aim of accelerating photocatalyst optimization. If successful, this work could have significant scientific broader impacts as there is great interest in establishing more efficient methods of harvesting energy from near IR to visible light to drive chemical reactions.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.