Plasmonics for Sustainability and Societal Impact

Metallic nanoparticles, used since antiquity to impart intense, vibrant color into materials, known in the 19th century as “Faraday’s colloid” and in the 21st as the optical readout of COVID antigen tests, are a central tool in the nanoscale manipulation of light. When excited by light, metallic nanoparticles undergo a coherent oscillation of their conduction electrons- known as a plasmon- which is responsible for their strong light-matter interactions and properties, as “optical antennas” or “plasmonic nanoparticles”. Light excitation gives rise to important properties: generation of nonequilibrium, “hot” electrons and holes that can drive chemical reactions very efficiently on the nanoparticle surface, and strong electromagnetic fields that give rise to ultrasensitive surface-enhanced Raman and IR spectroscopies (SERS and SEIRA) of adsorbate molecules. By coupling optical antennas and catalyst particles, one can transform traditionally thermocatalytic chemical reactions into photodriven reactions that proceed under surprisingly mild, low temperature conditions. This new type of light-based catalyst- an antenna-reactor nanoparticle complex- can be utilized for remediating greenhouse gases, converting them to useful molecules for industry, or into benign chemicals for a cleaner planet. As surface-enhanced spectroscopies surpass fifty years since their discovery, we can begin to apply machine learning strategies in simple ways to overcome some of their inherent limitations, making them more practical tools for the rapid and streamlined identification of toxic molecules in our environment and in ourselves.

Speaker: Naomi Halas, Rice University