Nanoparticles Adsorbed at the Water/Oil Interface: Coverage and Composition Effects on Structure and Diffusion

Abstract

Dissipative particle dynamics simulations are performed to study the structural and dynamical properties of various systems of nanoparticles accumulated at the water/oil interface. Homogeneous and Janus nanoparticles with different surface compositions are studied. For all nanoparticles, as the surface density increases, a transition from a liquidlike to a solidlike state is observed, as expected. At a high density of nanoparticles, hexagonal structures emerge and the nanoparticles' self-diffusion coefficient decreases because of caging effects. Similar results are observed for nanoparticles with different surface chemistry. Because different nanoparticles have different contact angles at the water/oil interface, the results obtained for systems containing mixed nanoparticles are more interesting. For example, our results show that the self-diffusion coefficient is not a monotonic function of the system composition, caused by the complex relation between hydrodynamic interactions and effective nanoparticle-nanoparticle interactions.