We characterize the dynamic and equilibrium adsorption of 5 nm gold NPs functionalized with ion-pair ligands at the toluene-water interface. We show that NP adsorption at the oil-water interface can be modulated by the pH and salt concentration. Partitioning of the NPs between the bulk aqueous phase and the interface is measured via absorbance spectroscopy for two different aqueous phase pHs (11.0 and 11.7) and over several orders of magnitude of aqueous phase NP concentration. The surface pressure of the interfacial film in equilibrium with the bulk aqueous phase is measured using the pendant drop method. We determine the range of surface pressure where the adsorption is reversible, as well as, conditions under which the adsorbed NPs are irreversibly adsorbed at the oil-water interface. We demonstrate that NP adsorption competes with the attachment of amphiphilic ions from the bulk phase.  We present a model for the Reversible adsorption of nanoparticles (NP) to oil-water interfaces that is based on a decrease in interfacial area and interaction between the particles. We show that the model describes well the equilibrium and dynamic conditions.<br/>

Competition between ions and nanoparticles during the reversible attachment of nanoparticles to a fluid interface

254th National Meeting (2017)

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