Solid particle stabilized emulsions (Pickering emulsions) provide interesting opportunities for the stabilization of liquid-liquid interfaces, for self-assembly on liquid interfaces and for the formation of colloidosomes. Besides, particles strongly adsorbed at a 2D interface are an important realization of a 2D model system in a 3D world. In various studies, it has already been reported that the physics in 2D, including the interparticle interactions and the phase transitions, is fundamentally different from 1D and 3D. What all interfacial studies performed so far have in common, is that the particles interpenetrate the oil-water interface as the colloids are wetted both by oil and water. Addition of salt to one of the phases can result in 2D (in plane) melting of a colloidal solid in these systems. In this presentation, we will discuss a surprising, new result: our particles could be detached from the interface by addition of salt only. Our results therefore indicate that the particles are not irreversibly trapped at the interface and hence this suggests that particles are non-touching, meaning that they are completely immersed in the oil phase. In principle, the entrapment of non-touching colloids near an oil-water interface could be theoretically explained by a balance between image charge attractions [1,2] and Van der Waals repulsions [3]. In this presentation, we will discuss these new experimental findings and describe the above discussed salt-effects.
[1] M. E. Leunissen, A. van Blaaderen, A. D. Hollingsworth, M. T. Sullivan, P. M. Chaikin, PNAS, 104, 2585-2590 (2007).
[2] J. Zwanikken, R. van Roij, Phys. Rev. Lett., 99, 178301 (2007).
[3] M. Oettel, Phys. Rev. E, 76, 041403 (2007).
N.A.Elbers@uu.nl
