Professor René Wasserman Award 2016 - Maria Ricci

“For the development of precise atomic force microscopy studies that have unveiled the limitations of the classical description of water at solid interfaces, and have shown the existence of long-lived entropy-driven ionic structures within the Stern layer.”

Wherever we look around us, interesting phenomena occur at interfaces, where liquids meet solids. Although interfaces are of molecular nature, most scientific research relies on macroscopic models to describe them. However, the specific molecular interactions and the complex chemistry are fundamental, for example, in heterogeneous catalysis, crystal growth, or body-antibody recognition. In the case of charged surfaces in aqueous media, the lateral organization of the adsorbed ions, guided by the water molecules solvating the surface (Stern Layer), plays a pivotal role in determining the properties of the interface. To achieve this level of description, we used high-resolution Atomic Force Microscopy (AFM). AFM can image single molecules by scanning the surface of a solid with a sharp probe immersed in liquid. For the first time, we detected single adsorbed ions by measuring the perturbation they induce on the local solvation environment of the surface. These experimental studies reveal ion-specific attractive ion-ion interactions: water is the driving force to induce order within the Stern Layer, creating hydration-correlation effects on mica and self-assembled monolayers. These studies provide experimental evidence of new interfacial mechanisms, paving the way for a more in-depth understanding of inorganic interfaces as well as living systems.