Core-shell particles are closely related to microgels with the difference that their cores are solid and consist of a different material than the shell. A particular example on how to achieve core-shell morphologies is the mixing rigid spherical colloids and soft interfacial components. This provides a wide playground to study interfacial phase behaviour, as the soft components can manipulate the interaction potential of the rigid colloidal particles. This modification results in unexpected self-assembly structures, including chain and square packing as minimum energy configurations.

Even though the fabrication of hexagonal colloidal monolayers is well established, it is far from trivial and the monolayer quality can fluctuate between individual samples and experiments. We recently identified that amphiphilic oligomeric species are present in polystyrene colloidal dispersions and can negatively affect the self-assembly behavior. We developed cleaning protocols and robust methods to circumvent the effect of impurities and reliably form well-ordered colloidal monolayers at liquid interfaces.