Maximizing the Harvesting of Photogenerated Electron-Hole Pairs in Hybrid Plasmonic Nanosystems

With support from the Macromolecular, Supramolecular and Nanochemistry Program (MSN) in the Division of Chemistry, Professor Prashant Jain of the University of Illinois Urbana-Champaign is developing materials, principles, and strategies for capturing visible light from solar radiation and deploying it in a directed and energy-efficient manner to form high-value chemical bonds. A particular target is the chemical bond between nitrogen and carbon atoms found in many high-value chemicals. Such light harvesting is currently achievable by nanometer-scale particles of coinage metals; however, the conversion of light to chemical energy is inefficient and uncontrolled. Professor Jain is addressing this challenge by using oxide minerals engineered on the nanometer scale to absorb visible light and produce energetic charges that survive long enough to be used productively for chemical energy generation. Furthermore, he is pairing these light-absorbing materials with chemical agents that direct and promote the flow of charge. If successful, the research will lead to technologies for manufacturing energetic reagents, fuels, and fine chemicals using renewable power and producing no carbon emissions. In public outreach activities, Professor Jain is also promoting sustainable technologies and practices through solar energy- and electricity-powered removal of nitrate pollutants from water sources near agriculture-dominated communities. The graduate students engaged in this project are gaining valuable experience in a wide range of chemical syntheses, spectroscopic and chemical kinetic analyses, and catalysis. This project is also providing opportunities for undergraduate researchers interested in sustainable technologies. Plasmonic nanostructures allow the harvesting of light in the form of energetic charge carriers, which can in turn be deployed to accelerate or drive chemical reactions. However, harvesting of light and light-to-chemical energy conversion via this scheme remains well below the thermodynamic efficiency limit. Professor Jain is applying a newer class of plasmonic materials and hybridization strategies for maximizing the separation of photogenerated electron–hole pairs and utilizing them more efficiently and selectively for reactions such as nitrogen–carbon bond formation. Specifically, Professor Jain is employing plasmonic metal oxide nanostructures, which are anticipated to exhibit slower carrier relaxation and recombination. The other strategies involve the hybridization of plasmonic metal oxide nanostructures with polar surfaces, water-oxidation promoters, and homogeneous catalysts. The work is expected to elucidate physicochemical and materials design factors that govern carrier separation and extraction and illustrate chemical architectures and schemes that are ideally suited for the directed and efficient flow of carriers on the nanoscale. These concepts coupled with the use of non-metallic plasmonic oxide nanostructures have the potential to expand the scope and reach of plasmonic chemistry for achieving energy-relevant chemical transformations. 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.