How the Electrochemical Double Layer Manipulates Molecule–Metal Interactions

Electrochemical interfaces are ubiquitous in sensing, catalysis, and energy storage, yet understanding molecular interactions with the electrochemical double layer (EDL) remains limited. Here, we use electrochemical surface-enhanced Raman spectroscopy (EC-SERS) to probe analyte-EDL interactions in real time. Precision SERS electrodes with robust electrochemically recleanable gold nanogaps allow us to detect subtle molecular spectral changes during cyclic voltammetry, revealing distinct intensity and frequency oscillations. Quantum mechanics/molecular mechanics simulations show that these effects arise from electrochemical potential-induced molecular reorientation and surface restructuring driven by dynamic interactions with the EDL. For sensing, this mechanism reduces detection limits for DNA nucleobases by more than 25-fold and enables label-free multiplexed sensing. Beyond improved sensor performance, this work provides a framework for understanding EC-SERS and gives insight into neutral molecule behavior within the EDL.