Free energy modelling of a spherical nanoparticle at an oil/water interface

Abstract

Interest in Pickering emulsions, which are stabilized by nanoparticles, has been driven by their superior stability and a desire to avoid the use of conventional surfactants. However, understanding of the chemical and physical phenomena governing particle stabilization at liquid/liquid interfaces remains limited because of the complexity of these systems. In particular, discrepancies can emerge between the inherent thermodynamic and the observed three-phase contact angles in such systems (particle/oil/water). We address this issue by modifying the classic equation for the free energy of a spherical nanoparticle at an oil/water interface. Our model defines the range of three-phase contact angles that enable successful Pickering stabilization. The model shows that the highest destabilization energy occurs when θ equals the position angle α, rather than 90°, as found in the conventional model. Our findings have significant implications for the identification of candidate Pickering stabilizers and the design of the emulsification process.