Optical Characterization of Large Icosahedral Colloidal Clusters (Part. Part. Syst. Charact. 2/2022)

Abstract

In article number 2100257, Ohnuki and co‐workers investigate the optical properties of massive spherical colloidal clusters with icosahedral structures. The spherical colloidal clusters with the icosahedral structure were discovered several years ago and show a unique triangular reflection pattern, which is expected to be applied to new optical materials such as pigments/dyes and colorimetric sensors.

Influence of Sphericity on Surface Termination of Icosahedral Colloidal Clusters

“…These color patterns originate from the crystalline arrangement of the Mackay core and anti-Mackay shell. [18,30] We have identified three distinct structural types in our study: onion-like clusters, partially icosahedral clusters, and fully icosahedral clusters. Their classification is rooted in the observed surface morphologies.…”

“…These color patterns originate from the crystalline arrangement of the Mackay core and anti‐Mackay shell. [ 18,30 ]…”

“…The orientation of the icosahedral clusters determines the color patterns, as elaborated in a prior report. [18,30] The triangular pattern emerges when the cluster aligns with a threefold axis face (3f) parallel to the substrate, which is made up of a hexagonal array within a truncated triangle. In cases where the twofold axis face (2f), composed of a square array inside a rectangle, aligns parallel to the substrate, a bowtie pattern is exhibited.…”

“…[ 18,19 ] Icosahedral clusters, however, are composed of 20 radially arranged tetrahedra in the Mackay core, with the anti‐Mackay shell extending outward. [ 17,24–30 ] These icosahedral clusters are not perfectly isotropic but provide consistent structural colors from radial stacks in tetrahedra across a wide range of orientations. Therefore, icosahedral clusters present promise for use as chemical‐free structural colorants in photonic inks, paints, and cosmetics.…”