Solvated Electron Generation from Coupled Plasmon Modes of Gold Nanoparticles Using Visible Light

Solvated electrons are strong homogeneous reducing agents, and their generation with visible light can unlock new redox chemistry. Water imposes a high photoemission energy barrier for gold, restricting the accessible spectral window for plasmon-mediated solvated electron generation to the near-ultraviolet region. Here, we first demonstrate that by using hexamethylphosphoramide, an organic solvent that supports large applied cathodic potentials without decomposition, the photoemission threshold is lowered to provide access to the entire visible spectrum. Next, we achieve solvated electron yields up to 150-fold higher with coupled plasmon modes from clustered gold nanoparticles, as compared to a smooth gold electrode. The observed quantum yield correlates with the local electric field enhancement by gap plasmon modes for these nanostructured electrodes as identified by varying the particle density. Overall, this study offers mechanistic insights into how coupled plasmon modes and threshold optimization can be used to enhance solvated electron generation with visible light.