Experimental and theoretical evidence for molecular forces driving surface segregation in photonic colloidal assemblies

Ming Xiao, Ziying Hu, Thomas E. Gartner, Xiaozhou Yang, Weiyao Li, Arthi Jayaraman, Nathan C. Gianneschi, Matthew D. Shawkey, Ali Dhinojwala*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

Surface segregation in binary colloidal mixtures offers a simple way to control both surface and bulk properties without affecting their bulk composition. Here, we combine experiments and coarse-grained molecular dynamics (CG-MD) simulations to delineate the effects of particle chemistry and size on surface segregation in photonic colloidal assemblies from binary mixtures of melanin and silica particles of size ratio (Dlarge/Dsmall) ranging from 1.0 to ~2.2. We find that melanin and/or smaller particles segregate at the surface of micrometer-sized colloidal assemblies (supraballs) prepared by an emulsion process. Conversely, no such surface segregation occurs in films prepared by evaporative assembly. CG-MD simulations explain the experimental observations by showing that particles with the larger contact angle (melanin) are enriched at the supraball surface regardless of the relative strength of particle-interface interactions, a result with implications for the broad understanding and design of colloidal particle assemblies.

Original languageEnglish (US)
Article numbereaax1254
JournalScience Advances
Volume5
Issue number9
DOIs
StatePublished - Sep 20 2019

ASJC Scopus subject areas

  • General

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