Peak Wavelength Mapping of Triangular Reflection in Spherical Colloidal Cluster with Icosahedral Symmetry

Spherical colloidal clusters have various types of particle arrangements. Interestingly, one type has an icosahedron symmetry, characterized by the existence of five-fold axes. When the colloidal particle size is comparable to the wavelength of light, icosahedral colloidal clusters exhibit a unique triangular reflection with a specific wavelength, owing to optical interference. In this paper, we report the results of a detailed optical study on the position-dependent peak wavelength within the triangular region. Based on the map of the peak wavelength and spectral shape, we propose a structural model of the icosahedral colloidal cluster and discuss its formation process.