Droplet confined binary colloidal co-assembly into hierarchical Supraparticles with controllable morphology.

Physically confined assembly of binary colloidal mixtures in emulsion droplets provides a versatile platform for engineering supraparticles with tunable morphologies and functionalities. While single-component and hard-sphere colloidal assemblies have been extensively studied, the co-assembly of binary soft colloids presents unresolved challenges in architecture control and functional integration. In this work, we investigate the co-assembly performance of emulsion droplet confined binary soft colloids of spherical polystyrene nanoparticles (PS) and wire-like carbon nanotubes (CNTs). The supraparticles of CNT/PS with various architectures have been obtained by varying the solvent removal dynamics and the binary colloidal composition. We find out that the binary colloidal size and mass ratio govern the CNT/PS supraparticle structural diversity, ranging from core-shell, core-semishell, garnet-like to densely packed architectures. Spontaneous emulsification and microphase segregation drive the transformation from core-shell to core-semishell architectures, revealing the critical role of fluid dynamics and confinement effects. This understanding of mechanism enables the rational design of hybrid magnetic supraparticles, demonstrating the broad applicability of such an approach. By establishing clear composition-structure correlations, this work advances the controlled co-assembly of binary colloids into hierarchical supraparticles, offering a pathway for constructing functional materials with tailored complexity.