Interfacial displacement of nanoparticles by surfactant molecules in emulsions

Charu Vashisth; Catherine P Whitby; Daniel Fornasiero; John Ralston

doi:10.1016/j.jcis.2010.05.089

Interfacial displacement of nanoparticles by surfactant molecules in emulsions

J Colloid Interface Sci. 2010 Sep 15;349(2):537-43. doi: 10.1016/j.jcis.2010.05.089. Epub 2010 Jun 1.

Authors

Charu Vashisth¹, Catherine P Whitby, Daniel Fornasiero, John Ralston

Affiliation

¹ Ian Wark Research Institute, University of South Australia, Mawson Lakes, SA 5095, Australia.

PMID: 20573356
DOI: 10.1016/j.jcis.2010.05.089

Abstract

The remarkable stability of nanoparticles attached to oil-water interfaces in macroemulsions hinders controlled detachment of these particles from emulsions. In this work it is shown that adding surfactant molecules which preferentially adsorb at the oil-water interface displaces nanoparticles from the interface. Surfactant adsorption at the oil-water interface is energetically favoured and readily occurs on mixing nanoparticle-stabilised oil-in-water emulsions with surfactant solutions. Depending on the surfactant concentration, there is a significant reduction in the interfacial tension. Hence there is substantial fragmentation of the oil droplets and foaming of the emulsion during mixing. Surfactant concentrations above the critical micelle concentration are required to achieve complete interfacial displacement and hence recovery of the nanoparticles from the emulsions. The effects of surfactant addition have important implications for tailoring the interfacial composition of emulsions.