Surface structure determines many of the most important properties of the common liquids; yet, only indirect measurements of the surface structure were possible until recently. Thus, liquid surfaces were conventionally assumed to be even more disordered than the bulk liquid. In the last decade, high-brilliance synchrotron light sources were built, and the surfaces of many liquids were proved to be highly-ordered. This work demonstrates some of the most striking results obtained by scattering x-ray radiation off the liquid surfaces, such as the surface layering in ionic liquids, promising "green" solvents of the 21th century. We demonstrate unique phase transitions in quasi-two-dimensional Langmuir-Gibbs films of alkanes on water. These phase transitions provide a new physical mechanism for spontaneous formation of oil-in-water emulsions; emulsion droplets are thermodynamically stabilized by interfacial crystallization. This unique mechanism of spontaneous emulsification is fully dependent on the geometry of the molecules involved; thus, we expect these surface ordering phenomena to be dramatically important in a wide range of systems in science and nanotechnology.
Eli Sloutskin, Ph.D. Since 2009, faculty member in the Bar-Ilan University Physics Department (Israel).