Pickering emulsions with low interface coverage but enhanced stability for emulsion interface catalysis and SERS-based detection

Particle adsorption at the oil-water interface is an important strategy for emulsion stabilization against coalescence, however, the particle occupation of the interface and the requirement of free interfaces in many applications is a contradiction. We report an emulsion type with low droplet surface coverage but enhanced stability by employing colloidal rings as emulsifiers. The formed emulsions provide a large accessible oil-water interface (>80%). The enhanced diffusion through the interface and highly efficient loading of catalytic nanoparticles at the interface result in much higher catalytic efficiency than the nanosphere-covered emulsions in both batch and continuous flow interface catalysis. The loading of plasmonic nanoparticles brings excellent performance in surface-enhanced Raman spectroscopy-based detection, which exhibits the lowest detectable concentration as low as 10−11 M using only 0.25 μL of analyte and 0.2 μg of Au nanoparticles. The ring-based Pickering emulsion provides freedom for designing interface structures and compositions for functional emulsions. Particle adsorption at the oil-water interface is an important strategy for emulsion stabilization against coalescence but achieving free interfaces at the same time remains challenging. Here the authors report an emulsion with low droplet surface coverage but enhanced stability by employing colloidal rings as emulsifiers.