Emulsification of immiscible two-phase fluids, i.e., one condensed phase dispersed homogeneously as tiny droplets in an outer continuous medium, plays a key role in medicine, food, chemical separations, cosmetics, fabrication of micro-and nanoparticles and capsules, and dynamic optics. Herein, we demonstrate that water clusters/droplets can be formed in an organic phase via the spontaneous assembling of ionic bilayers. We term these clusters ionosomes, by analogy with liposomes where water clusters are encapsulated in a bilayer of lipid molecules. The driving force for the generation of ionosomes is a unique asymmetrical electrostatic attraction at the water/oil interface: small and more mobile hydrated ions reside in the inner aqueous side, which correlate tightly with the lipophilic bulky counterions in the adjacent outer oil side. These ionosomes can be formed through electrochemical (using an external power source) or chemical (by salt distribution) polarization at the liquid-liquid interface. The charge density of the cations, the organic solvent, and the synergistic effects between tetraethylammonium and lithium cations, all affecting the formation of ionosomes, were investigated. These results clearly prove that a new emulsification strategy is developed providing an alternative and generic platform, besides the canonical emulsification procedure with either ionic or nonionic surfactants as emulsifiers. Finally, we also demonstrate the detection of individual ionosomes via single-entity electrochemistry.
Bibliographical noteFunding Information:
D.M. and H.D. thank the Israel Science Foundation (Contract No. 641/18) and the National Natural Science Foundation of China (Grant No. 21904143) for financial support. P.P. and S.M. are grateful for the financial support from the Swiss National Science Foundation under Grant Ambizione Energy 160553. P.P. also gratefully acknowledges the Academy Research Fellow funding (Grant No. 315739) and project funding (Grant No. 334828) from the Academy of Finland. E.S. is grateful to the Development Program of Lomonosov Moscow State University and the Russian Science Foundation (Grant No. 19-13-00283). H.H.G. acknowledges the Swiss National Science Foundation grants: 200021_175745 “Photo Induced Charge Transfer Reaction at Molecular Interfaces: towards new routes of solar energy storage” and 20SC-1_193608 “Photoproduction of hydrogen in biphasic systems with electron donor recycling (PHOTO2H)”.
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