Combining Experimental and Simulation Approaches to Model Color Generation in Colloidal Assemblies Under Spherical Confinement*

Structural colors are produced by constructive interference of specific wavelengths of light as it moves through a nanostructured material. Inspired by the mechanism of structural color production in avian species, researchers have fabricated colloidal glasses using either non-absorbing particles (like silica) or highly absorbing particles (like melanin). Modeling color generation from such systems have posed challenges in terms of elucidating the structural characteristics of the colloidal assembly, handling multiple scattering, and accounting for large refractive index contrast and high broadband absorption. In this work, we present a robust method of performing optical modeling using experimental and simulation tools that includes a) extraction of structural information from colloidal assemblies using scattering techniques, b) reconstruction of the assemblies using the previously developed CREASE method, and c) optical simulation of the reconstructed structures using finite-difference time-domain calculations to produce reflectance profiles that match the experimental reflectance spectra. This full-cycle approach presents opportunities to model and predict color generation from complex hierarchical structures that can open exciting avenues to tune structural colors.