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

doi:10.1126/sciadv.aax1254

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

Chemistry

Research output: Contribution to journal › Article › peer-review

23 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 (D_large/D_small) 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 language	English (US)
Article number	eaax1254
Journal	Science Advances
Volume	5
Issue number	9
DOIs	https://doi.org/10.1126/sciadv.aax1254
State	Published - Sep 20 2019

Funding

We acknowledge support from the Air Force Office of Scientific Research (MURI-FA 9550-18-1-0142, FA9550-18-1-0477, and FA9550-13-1-0222), the National Science Foundation (EAR-1251895, DMR-1105370, and DMR-1609543), and Research Foundation—Flanders (FWO G007117 N). This work made use of the BioCryo facility of Northwestern University’s NUANCE Center, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205); the MRSEC program (NSF DMR-1720139) at the Materials Research Center; the International Institute for Nanotechnology (IIN); and the State of Illinois, through the IIN. This research was supported in part through the use of computational resources from the University of Delaware (Farber cluster) and the Extreme Science and Engineering Discovery Environment (XSEDE) Stampede cluster (allocation MCB100140), which is supported by NSF grant ACI-1548562. Author

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title = "Experimental and theoretical evidence for molecular forces driving surface segregation in photonic colloidal assemblies",

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.",

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AU - Xiao, Ming

AU - Hu, Ziying

AU - Gartner, Thomas E.

AU - Yang, Xiaozhou

AU - Li, Weiyao

AU - Jayaraman, Arthi

AU - Gianneschi, Nathan C.

AU - Shawkey, Matthew D.

AU - Dhinojwala, Ali

PY - 2019/9/20

Y1 - 2019/9/20

N2 - 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.

AB - 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.

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

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