Xiao, MingHu, ZiyingGartner, Thomas E., IIIYang, XiaozhouLi, WeiyaoJayaraman, ArthiGianneschi, Nathan C.Shawkey, Matthew D.Dhinojwala, Ali2019-11-142019-11-142019-09eaax1254http://hdl.handle.net/10919/95550Surface 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 similar 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.application/pdfenCreative Commons Attribution-NonCommercial 4.0 InternationalArticle - Refereedhttps://doi.org/10.1126/sciadv.aax125459315557342375-2548