Fabrication of nonspherical or marcoporous particles using emulsion droplets as confining geometries

We present the fabrication method for the nonspherical or macroporous particles such as binary colloidal aggregates or shape-anisotropic particles from water-in-oil emulsions as confining geometries for the self-organization. Here, the water droplets contained various combinations of two different colloids: monodisperse silica or polystyrene microspheres for larger particles and silica or titania nanoparticles for smaller particles. For each combination, the configurations of the large microspheres were not changed by the presence of the small particles though the arrangement of the smaller particles was strongly dependent on the nature of the electrostatic interparticle interactions between small and large particles inside the water droplets. The experimentally observed structural evolutions were consistent with the predicted morphologies calculated using Surface Evolver simulation tool. The nonspherical macroporous particles were also successfully prepared by self-organizing amidine-coated latex microspheres and smaller inorganic nanoparticles, followed by the subsequent calcinations for burning out the organic microspheres.