Self-Assembly of TiO₂ Nanofiber-Based Microcapsules by Spontaneously Evolved Multiple Emulsions

We demonstrate hierarchical nest/crust-like colloidosomes composed of interlocked titanium dioxide (TiO₂) nanofibers using spontaneously evolved n-butanol/water/ n-butanol (B/W/B) emulsions. We find two mechanisms to produce colloidosomes from B/W/B droplets due to their mutual solubility and dewetting discrepancy. Porous TiO₂ colloidal capsules with loosely intertwined nanofibers were obtained after the dewetting of nanofiber-coated B/W/B droplets, while crustlike TiO₂ colloidosomes with a thin shell and large hollow interior are developed from amphiphilic polymer-stabilized B/W/B droplets. We further investigate the effect of experimental parameters, including the initial droplet size, the nanofiber concentration, and the water/butanol ratios in butanol phases, on the droplet-to-colloidosome evolution and resultant morphology of colloidosomes. Our simple and versatile approach for fabricating TiO₂ colloidosomes can be extended to a range of irregular colloidal particles, and the products have great potential to act as host systems in electrochemical catalysis, photothermal therapy, or filtration materials.