Interactions between water and organic molecules or inorganic salts on surfaces

Water, as a ubiquitous and relatively inert medium, plays a vital role in nature. The interactions between water and organic molecules or inorganic salts are of fundamental interest in understanding hydration processes in chemistry. The combination of scanning probe microscopy and theoretical calculations provides a versatile tool to directly visualize and further rationalize such interactions as well as influences of water on organic molecules and inorganic salts. In this review, we provide a brief overview of the recent exciting progress in revealing the interactions between water and organic molecules as well as inorganic salts (including ions) on surfaces. Herein, we describe first steps of hydration of organic molecules followed by a microsolvation process on surfaces. Subsequently, water‐induced tautomerization and chiral separation of small biomolecules on surfaces are discussed for understanding the roles of water in driving biological self‐assembly processes. Moreover, water is also able to assist structural transformation globally by selectively interrupting the relatively weak hydrogen bonds within nanostructures. Based on the water‐incorporated molecular nanostructures, dissolution of sodium halides on wet surfaces is achievable using confined water, while hydrates of halide ions desorb from the surface. More interestingly, ion hydrates are also demonstrated to be artificially accessible, which enables atomic‐scale investigation into local ion hydration and transport at interfaces. This review provides new insights into the role of water in the hydration‐related molecular and ionic systems, with implications for hydration and solvent effects down to the single‐molecule level.