Nanoparticle assembly at a fluid-fluid interface is a proven route to precisely engineer organic/inorganic materials with controlled optical properties. In this talk, we will present our recent work using coarse-grained Langevin dynamics simulation that mimics reverse-emulsion (aqueous droplet in octanol) directed assembly of binary nanoparticle mixtures into supraballs. We model a binary mixture of silica and synthetic melanin particles in implicit solvent within a shrinking spherical confinement to replicate the shrinking reverse-emulsion droplet as the water diffuses from inside the droplet into the octanol phase. The simulation protocol captures the physics of this reverse-emulsion assembly by reproducing the experimental observation of melanin and/or smaller nanoparticles enriching the water-octanol interface. For all binary mixtures, we observe enrichment of the melanin particles at the supraball surface as compared to interior of supraball. This enrichment decreases with increasing melanin/silica size ratio. We observe appreciable crystalline ordering only in systems where the particles are of similar size and that particle size dispersity, finite assembly timescale, and curvature of the supraball surface all serve to suppress particle ordering. These findings serve as design rules for tailoring the supraballs for structural color applications and improve our fundamental understanding of particle assembly near curved interfaces.

Development of surface composition and ordering during reverse-emulsion assembly of binary colloidal particle mixtures

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.