Synthesis and aggregation behavior of hybrid amphiphilic titania Janus nanoparticles via surface-functionalization in Pickering emulsions

Amphiphilic surface-functionalized titania nanoparticles were prepared in a Pickering emulsion applying hydrophobic or hydrophilic agents containing a phosphonate anchor group. The Pickering emulsion approach allows for the formation of anisotropic nanoparticles with a high degree of surface-functionalization that mimic the behavior of surfactants. Therefore, the efficiency of the formed particles in stabilizing emulsions was studied and it could be shown that the stability of emulsions substantially increases by addition of amphiphilic particles. Due to the photocatalytic activity of anatase nanoparticles the emulsions stability against creaming can be decreased by irradiation with UV light. The critical micelle concentration (CMC) of suspensions of amphiphilically modified nanoparticles was determined by conductivity measurements. The prepared surface-functionalized nanoparticles show similar characteristics as amphiphilic block copolymers.