Structure and phase behavior of two-dimensional solids formed at interfaces

Abstract

Molecular monolayers adsorbed to solid surfaces such as graphite are distinct from the bulk in their physicochemical properties because of the 2D nature. In most cases, they form a well-defined 2D crystalline solid. We have been investigating such systems of various simple molecules by means of the synergetic use of X-ray diffraction, neutron scattering, and calorimetry. Selected examples illustrate that the reduced dimensionality has important consequences for the structure, dynamics, and phase behavior in the condensed state. In some cases, the similar solid monolayers are formed at the liquid-graphite interfaces, where they also show a rich variety of the structure and phase behavior. For the multicomponent system of those monolayers, mixing behavior is particularly interesting from both the structural and thermodynamic points of view. We also investigated ice crystallization from the solution, where a 2D nature was found in structure in the initial stage of crystallization.