Formation and ordering of nanomaterials in liquid-air and in liquid-liquid interfaces are fascinating phenomena and can be probed in-situ very efficiently with synchrotron X-ray scattering techniques. We shall discuss here two of our recent results as examples to illustrate this subject.

The first example is the counter intuitive reversible crystallisation of two-dimensional monolayer of Trisilanolisobutyl Polyhedral Oligomeric SilSesquioxane (TBPOSS) on water surface. Amphiphilic TBPOSS form rugged monolayers and Grazing Incidence X-ray Scattering (GIXS) measurements reveal that the in-plane inter-particle correlation peaks, characteristic of two-dimensional system, observed before transition is replaced by intense localized spots after transition.

The other example is the formation CuS single-crystals at the water–toluene interface through an interfacial reaction. Nano-crystallites of CuS form within a few minutes at the interface as the reagents are brought from the organic (upper) and aqueous (lower) layers to the interface, then crystallization of CuS proceeds over a few hours only by reorganization. The interface confinement and passivation by organics is critical here in the formation of single crystals having sizes of 6 and 200 nm along the normal and in-plane directions of the liquid–liquid interface.