Bidirectional Nanoparticle Crossing of Oil-Water Interfaces Induced by Different Stimuli: Insight into Phase Transfer

摘要

Gold nanoparticles (NPs) coated with stimuli-responsive polymer brushes are reported that readily transfer from oil to salty water aross the planar interfaces when the environmental temperature is reduced below 5 °C, while they transfer from salty water to oil when the environmental temperature returns to room temperature. The water-to-oil particle transfer after warming is dictated by the ionic strength of the aqueous phase, which is directly associated with the ionic strength reponse of the polymer brushes anchored on the NPs. In contrast, the temperarure onset for the oil-to-water NP transfer after cooling is weakly correlated with the transition temperature of the polymer brushes in either of the bulk phases. The transfer mechanism disparity for the two directions during NP crossing of oil-water interfaces should provide a better thermodynamic picture to describe phase transfer.