Physicochemical characterization of the interfacial behaviour of Janus nanoparticles

Abstract

Janus nanoparticles (JPs) are colloidal entities in which there are two differentiated spatial domains with different physicochemical properties. This anisotropy can lead to the spontaneous self-assembly of nanoparticles when exposed to an external stimulus such as a magnetic or electric field, pH or temperature gradients, etc. In particular, JPs with a wettability contrast between the two spatial domains are able to stabilize Pickering emulsions and provide the benefits from traditional molecular amphiphiles, e.g. the orientation of the hydrophobic and hydrophilic parts towards the oil and water phase in a water/oil interface, and the benefits of Pickering emulsions, e.g. the enhanced stabilization of foams and emulsions stabilized by nanoparticles due to the nanoparticles being in contact with each other and preventing the coalescence or the Ostwald ripening. Nevertheless, the different synthesis routes of JPs are costly and produce really small amounts of nanoparticles at the laboratory scale. Thus, it is important to verify if the JPs are better than the corresponding homogeneous nanoparticles (HPs), much easier to synthesize and already widely applied in the industry as foam and emulsion stabilizers. But the small amounts synthesized does not allow to perform easy tests in which a emulsion is formed with JPs and in this thesis we propose a collection of several techniques to characterize the interfacial activity of such JPs at water/air and water/oil interfaces.