Modifications in surfactant-dependent phase behavior of colloidal nanoparticles under charge reversal

Abstract

Modifications in the surfactant (ionic and non-ionic)-dependent phase behavior of the anionic silica nanoparticles have been investigated under charge reversal as induced through multivalent counterions. The stable one-phase system of nanoparticles-anionic surfactant transforms into a two-phase (aggregates) state on the addition of tetravalent electrolyte (ZrCl4). On the other hand, the two-phase nanoparticle-cationic surfactant system becomes one-phase in the presence of ZrCl4. Interestingly, for nanoparticle-non-ionic surfactant system, stable micelle-decorated one-phase undergoes transformation to a two-phase with increasing ZrCl4 concentration. The modifications in the phase behavior have been explained by the structural evolution and interplay of the underlying interactions in the system.