Nanoparticle-stabilised emulsions: droplet armouring vs. droplet bridging.

We speculate that the ability of small nanoparticles to stabilise emulsions via droplet bridging is controlled by the balance between an energy increase, due to the interaction between two oil-water interfaces in close proximity through surface forces, and an energy decrease due to the adsorption of a bridging particle on two oil-water interfaces. For nanoparticles of diameter greater than about 10 nm, tuning this interaction may render bridging possible, whereas nanoparticles smaller than 10 nm may stabilise emulsions only via the formation of dense layers of adsorbed particles on droplets. Both predictions are experimentally testable.