Solid and hollow nanoparticles templated using non-ionic surfactant-based reverse micelles and vesicles

Surfactants play a critical role in nanoparticle morphology control in microemulsion-mediated synthesis. Herein tuning the morphology of silica nanoparticles from solid to hollow is investigated by varying the phase structure within reverse microemulsions using a non-ionic surfactant (Triton X-100, TX100). Assisted with dynamic light scattering and rheology, it is found that increasing the concentration of TX100 leads to a transition from small reverse micelles to larger double-layered reverse vesicles. Transmission Electron Microscopy is employed to show this phase change corresponds to the synthesis of solid and hollow silica nanoparticles, respectively. It is also found that adding another co-surfactant, ethanol, is also able to tune the synthesized particles from solid to hollow, as well as the shell thickness of the hollow nanoparticles. This study shows how the microemulsion phase structure can be used to tune the morphology of nanoparticles.