Surface Tension Drives the Orientation of Crystals at the Air−Water Interface

Nicolas R. Chevalier (1) , Patrick Guenoun (1)

1 LIONS - Laboratoire Interdisciplinaire sur l'Organisation Nanométrique et Supramoléculaire

The fabrication of oriented crystalline thin films is essential for a range of applications ranging from semiconductors to optical components, sensors, and catalysis. Here we show by depositing micrometric crystal particles on a liquid interface from an aerosol phase that the surface tension of the liquid alone can drive the crystallographic orientation of initially randomly oriented particles. The X-ray diffraction patterns of the particles at the interface are identical to those of a monocrystalline sample cleaved along the {104} (CaCO 3) or {111} (CaF 2) face. We show how this orientation effect can be used to produce thin coatings of oriented crystals on a solid substrate. These results also have important implications for our understanding of heterogeneous crystal growth beneath amphiphile monolayers and for 2D self-assembly processes at the air−liquid interface. T he first crystals to grow from a supersaturated aqueous solution often nucleate at the air−water interface. This can happen for a variety of reasons. When crystallization is induced by cooling of a hot, saturated salt solution, for example, faster cooling at the air−water interface makes the super-saturation highest at this location. CaCO 3 nucleation from hard water occurs first at the interface because gaseous CO 2 resulting from the reaction Ca 2+ + 2 HCO 3 −

Domaines: Matériaux

Nicolas R. Chevalier, Patrick Guenoun. Surface Tension Drives the Orientation of Crystals at the Air−Water Interface. Journal of Physical Chemistry Letters, 2016, 7, pp.2809-2813. ⟨10.1021/acs.jpclett.6b01312⟩. ⟨cea-01345285⟩