Coupled Au Nanoparticle-Cavity Nanostructures for Precise Control in Resonance-Driven Photocatalytic Reactions

Photocatalysis offers a sustainable approach to converting solar energy into chemical energy, enabling the production of renewable fuels and chemicals with net-zero emissions, a crucial step toward a renewable energy-based economy. Recent advancements in nanophotonics, particularly in plasmonic hybridized nanostructures, have enabled tunable localized surface plasmon resonances, offering solutions for selective, resonance-driven chemical applications via two nonthermal mechanisms: near-field enhancement, which amplifies the localized electromagnetic field, and hot electron energy transfer, which injects energetic electrons into reactants. We designed a series of self-assembled Au nanoparticle cavities to precisely control plasmonic resonance strength via Fabry-Pérot (F-P) resonances by tuning the TiO₂ cavity thickness. The strong coupling between plasmonic and F-P modes can be strategically exploited to either enhance or suppress a model reaction, the photodegradation of methylene blue. By tuning the F-P node or peak to achieve spatial and spectral overlap with the plasmonic resonance, we can facilitate and enhance the reaction. Specifically, this approach enhances the product yield by a factor of 102, from 0.07 to over 7.18, as determined by the integration of the vibrational peak of the product at 480 cm^-1 in the Raman spectrum. These findings demonstrate that plasmonic hybridized nanostructures enable control over reactions to modulate the desired product yield. In this work, we demonstrate a strategy for optically manipulating reaction rates to either enhance target products or suppress it. This approach advances the selective control of photocatalysis, offering opportunities to enhance conversion processes, and has potential applications in renewable fuel production.