Structural analysis of confined monovalent salts: Combined effects of steric hindrance, surface charge representation, and dielectric response

Abstract

The precise ion determination at solid-liquid interfaces and the underlying mechanisms behind this are of paramount relevance in a wide range of technological, environmental and biological applications. In this work, a systematic exploration into the behavior of monovalent salts in an extended nanospace is performed with Monte Carlo simulations in an attempt to provide a more general description. We obtain rather useful information not only on the lateral organization of ions in the Stern layer region but also on their distribution in the direction normal to the interface. Our simulation results show a remarkably consistent picture with the experimentally observed Stern layer structure in the discrete surface charge representation. It is recognized that sensitive to the radii of hydrated counterions and the solution dielectric response, their binding to low-dielectric interface sites forming a set of Bjerrum pairs is crucially driven by electrostatics. Also, we evaluate the validity of the uniform surface charge modeling that underlies previous theories and numerical simulations in predicting the structural properties of monovalent salts under confinement.