Freeze-fracture shadow-casting (FreSCA) cryo-SEM as a tool to investigate the wetting of micro- and nanoparticles at liquid-liquid interfaces.

Since the seminal work of Pickering and Ramsden more than a century ago, adsorption of solid micro- and nanoparticles at the interface between two fluids has been recognized as a means to enormously improve emulsion stability against coalescence. Despite their long-standing use in a vast range of practical applications, several key issues regarding the behavior of small objects at liquid interfaces still remain unresolved. In particular, current techniques fail to investigate the properties of individual particles smaller than 500 nm. An exception to this scenario is a technique that we have recently developed, based on freeze-fracture cryo-SEM, which for the first time makes it possible to measure the wetting properties of single nanoscale objects through a metal shadow-casting protocol. In this work we present additional details and results which showcase the potential of this novel tool as the benchmark for in situ characterization of particles at interfaces.