Unmodified Clay Nanosheets at the Air-Water Interface*

Clay nanolayers are 2D soft materials, such as graphene oxide layers. Clay nanolayers are of great general interest, in particular, because of their use as Pickering emulsion stabilizers and their ability to provide colloidosome capsules.  Many reports show that clays could only adhere at oil-water or air-saline-water interfaces in the aggregated state. However, here we demonstrated that unmodified clay nanolayers can be located at air-deionized-water interfaces. In the present work, we use a clay nanolayer made by a synthetic Fluorohectorite with a very high aspect ratio, superior quality in homogeneity and charge distribution. We studied clay nanosheet organization at the air-water interface by combining different experimental methods: Langmuir film studies show insignificant surface tension when the clay particles are at the surface, whereas Grazing Incidence X-ray Off Specular Scattering (GIXOS) confirmed the presence of unmodified and functionalized clay nanosheets at the air-water interface, and Brewster Angle Microscopy (BAM) demonstrated a dynamic equilibrium between unmodified clay nanolayers on the air-liquid interface and the subphase.