Optical Suppression of Energy Barriers in Single Molecule-Metal Binding

Understanding the interactions between molecules and metal surfaces is of widespread importance in electrochemistry, sensing, medical imaging/targeting, molecular electronics and spintronics. Although many techniques have characterized the molecule-metal transient bonds, conflicting conclusions arise from their buried location and heterogeneity, while single-molecule probes are scarce. Confinement of optical fields to picometre length-scales around adatoms (termed picocavities [1] , Fig. 1a ) has enabled tip-enhanced and surface-enhanced Raman spectroscopies (TERS and SERS, Fig. 1e ) of single-molecules. However how adatoms change with molecule-metal interactions, with light (both key ingredients in photocatalysis), and how they link to picocavity formation in metal nanogaps is not understood.