Probing solid/liquid interfaces at a single-molecule level by in-situ break junction techniques

Probing structure, dynamics, and chemical reactions at an interface with a single-molecule level is fundamentally important for elucidating the structure-activity relationships in chemistry, physics and materials science. Recently, single-molecule electrical measurements by break junctions that widely employed to study charge transfer in molecular junctions, have been developed to explore the single-molecule physics and chemistry. Here, the primary advances of significant physical and chemical phenomena at solid/liquid interfaces investigated by scanning tunneling microscopy break junctions (STM-BJ) and mechanically controllable break junction (MCBJ) techniques, have been highlighted and summarized in five regimes: (1) Chemical reactions induced by electric field, light and electrochemical potential; (2) Molecular adsorption including the metal-molecule interaction, surface coverage and adsorption free energy; (3) Interfacial acid−base chemistry; (4) Molecular isomerization; (5) Integrating break junctions with Raman characterization. The principles of these single-molecule electrical measurement and corresponding results are illustrated and discussed in details. Such single-molecule measurements provide a uniform opportunity to detect molecular information at the solid/liquid interface.