Controlled assembly of icosahedral colloidal clusters for structural coloration

Cheolho Kim, Kinam Jung, Ji Woong Yu, Sanghyuk Park, Shin Hyun Kim, Won Bo Lee, Hyerim Hwang, Vinothan N. Manoharan, Jun Hyuk Moon

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

Icosahedral colloidal clusters are a new class of spherical colloidal crystals. This cluster allows for potentially superior optical properties in comparison to conventional onion-like colloidal supraballs because of the quasi-crystal structure. However, the characterization of the cluster as an optical material has until now not been achieved. Here we successfully produce icosahedral clusters by assembling silica particles using bulk water-in-oil emulsion droplets and systematically characterize their optical properties. We exploit a water-saturated oil phase to control droplet drying, thereby preparing clusters at room temperature. In comparison to conventional onion-like supraballs with a similar size, the icosahedral clusters exhibit relatively strong structural colors with weak nonresonant scattering. Simulations prove that the crystalline array inside the icosahedral cluster strengthens the collective specular diffraction. To further improve color saturation, the silica particles constituting the cluster are coated with a thin-film carbon shell. The carbon shell acts as a broad-band absorber and reduces incoherent scattering with long optical paths, resulting in vibrant blue, green, and red colors comparable to inorganic chemical pigments.

Original languageEnglish
Pages (from-to)9704-9712
Number of pages9
JournalChemistry of Materials
Volume32
Issue number22
DOIs
StatePublished - 24 Nov 2020

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