Materials will segregate to the interface between two immiscible fluids to reduce the interfacial energy.  Per particle, the reduction in the interfacial energy will depend upon the size and shape of the particle and, to a first approximation, the cross-sectional area of the particle at the interface. So, for example, nanosheets, like graphene or clays, will occupy a large interfacial area and result in a significant reduction in the interfacial energy per particle or sheet.  Nanorods, like carbon nanotubes or tobacco mosaic virus, will orient parallel to the interface to maximize the reduction in the interfacial energy and, in fact, can form a two-dimensional liquid crystalline phase at the interface to optimize packing coverage of the interface.  Nanoparticles, with the smallest cross-sectional area, are only weakly held at the interface where the reduction in interfacial energy competes against thermal energy, resulting in liquid like assemblies at the interface.  One route to enhance the interfacial activity is to generate Janus-type particles, where one part is soluble in one fluid, while the second is soluble in another. The interfacial activity of these different types of nanoscopic materials will be discussed along with relevant applications.

On the interfacial behavior of nanomaterials: From nanoparticles to nanorods to nanosheets

246th National Meeting (2013)

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