Probing Solvent Dynamics at the Single-Molecule Limit
Roberto Listo, James M. F. Morris, Amit Sil, Xiaohang Qiao, R. Tom Abram, Chanyuan Huo, Jonathan S. Ward, Walther Schwarzacher, Piero Malcovati, Marco Vacca, Mariagrazia Graziano, Giovanna Turvani, Richard J. Nichols, Andrea VezzoliAbstract
The Electric Double Layer (EDL) that self-organizes at electrode–electrolyte interfaces plays a fundamental role in electrochemistry. While its structure has been extensively studied over the last 150 years, its dynamic behavior is still not completely understood. Here, we present a novel experimental approach to probe the EDL using single-molecule junctions as ultrasensitive probes, validated by a preliminary study of the Inner Helmholtz Plane (IHP). We measured the current response of single-molecule devices under square-wave bias in various solvent environments, and we found remarkable differences falling into three categories: large nonlinear transients in highly polar solvents, capacitor-like responses in solvents of intermediate polarity, and no significant transients (within our frequency limits) in nonpolar solvents. By fitting the solvent behavior to a molecular-level equivalent circuit, our data reveal trends in how the nature of the solvent influences IHP dynamics and provide insights into the origin of nonlinearity.