Pickering Foams Stabilized by α-Zirconium Phosphate-Propylamine Nano-Sheets

We demonstrate the stabilization of Pickering foams utilizing partially hydrophobic inorganic nano-sheets with a thickness at atomic scale. The nano-sheets are obtained by intercalation and exfoliation of ZrP crystals using propylamine as a guest molecule. Subsequently, the hydrophobicity of the nano-sheets is adjusted by adsorbing different quantities of propylamine using the ion-exhange properties of ZrP. The adsorption of propylamine on the nano-sheet surfaces grants an inherent hydrophobicity that enables the nano-sheets to adsorb on the air-water interface. The foam stability was studied by calculating the rate of water drainage as a function of time. The foams exhibit excellent stability even at low nano-sheet concentrations. In addition, the foam-to-water ratio was evaluated by varying the nano-sheet concentration and the degree of hydrophobicity. Cross-polarizing micrographs and scanning electron microscopy observations revealed the adsorption of the ZrP-propylamine nano-sheets on the air-water interface. We observed that the foams are stabilized by several layers of nano-sheets that prevent the diffusion of gas between the bubbles.