Structural Color Production in Melanin‐Based Disordered Colloidal Nanoparticle Assemblies in Spherical Confinement. Issue 5 (29th December 2021)

• Record Type: Journal Article
• Authors: Patil, Anvay; Heil, Christian M.; Vanthournout, Bram; Bleuel, Markus; Singla, Saranshu; Hu, Ziying; Gianneschi, Nathan C.; Shawkey, Matthew D.; Sinha, Sunil K.; Jayaraman, Arthi; Dhinojwala, Ali
• Is Part Of: Advanced optical materials. Volume 10:Issue 5(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-12-29
• Subjects: biomimicry -- broadband absorption -- colloidal assembly -- optical modeling -- structural colors -- structure–property relationship -- synthetic melanin; Optical materials -- Periodicals; Photonics -- Periodicals; 620.11295
• DOI: 10.1002/adom.202102162
• Languages: English
• ISSNs: 2195-1071

Abstract

Abstract: Melanin is a ubiquitous natural pigment that exhibits broadband absorption and high refractive index. Despite its widespread use in structural color production, how the absorbing material, melanin, affects the generated color is unknown. Using a combined molecular dynamics and finite‐difference time‐domain computational approach, this paper investigates structural color generation in one‐component melanin nanoparticle‐based supraparticles (called supraballs) as well as binary mixtures of melanin and silica (nonabsorbing) nanoparticle‐based supraballs. Experimentally produced one‐component melanin and one‐component silica supraballs, with thoroughly characterized primary particle characteristics using neutron scattering, produce reflectance profiles similar to the computational analogs, confirming that the computational approach correctly simulates both absorption and multiple scattering from the self‐assembled nanoparticles. These combined approaches demonstrate that melanin's broadband absorption increases the primary reflectance peak wavelength, increases saturation, and decreases lightness factor. In addition, the dispersity of nanoparticle size more strongly influences the optical properties of supraballs than packing fraction, as evidenced by the production of a larger range of colors when size dispersity is varied versus packing fraction. For binary melanin and silica supraballs, the chemistry‐based stratification allows for more diverse color generation and finer saturation tuning than does the degree of mixing/demixing between the two chemistries. Abstract : This work combines molecular dynamics and finite‐difference time‐domain computational approaches to study structural color production from melanin nanoparticle‐based supraparticles. The fundamental knowledge of how melanin controls and alters color will be valuable for engineering synthetic optical materials for applications in paints, coatings, cosmetics, and food colorings.