title: Dopamine-melanin nanofilms for biomimetic structural coloration.
abstract: This article describes the formation of dopamine-melanin thin films (50-200 nm thick) at an air/dopamine solution interface under static conditions. Beneath these films, spherical melanin granules formed in bulk liquid phase. The thickness of dopamine-melanin films at the interface relied mainly on the concentration of dopamine solution and the reaction time. A plausible mechanism underlining dopamine-melanin thin film formation was proposed based on the hydrophobicity of dopamine-melanin aggregates and the mass transport of the aggregates to the air/solution interface as a result of convective flow. The thickness of the interfacial films increased linearly with the dopamine concentration and the reaction time. The dopamine-melanin thin film and granules (formed in bulk liquid phase) with a double-layered structure were transferred onto a solid substrate to mimic the (keratin layer)/(melanin granules) structure present in bird plumage, thereby preparing full dopamine-melanin thin-film reflectors. The reflected color of the thin-film reflectors depended on the film thickness, which could be adjusted according to the dopamine concentration. The reflectance of the resulted reflectors exhibited a maximal reflectance value of 8-11%, comparable to that of bird plumage (∼11%). This study provides a useful, simple, and low-cost approach to the fabrication of biomimetic thin-film reflectors using full dopamine-melanin materials.
authors.affiliation: Department of Chemistry, Research Institute of Natural Sciences, Incheon National University , 119 Academy-ro, Yeonsu-gu, Incheon 406-772, Republic of Korea.
authors.forename: Tong-Fei
authors.initials: TF
authors.lastname: Wu
authors.forename: Jong-Dal
authors.initials: JD
authors.lastname: Hong
mesh_terms: D040761:Biomimetic Materials / Q000737:chemistry*; D003116:Color; D008543:Melanins / Q000737:chemistry*; D036103:Nanotechnology / Q000379:methods*; D019999:Pharmaceutical Solutions / Q000737:chemistry*
chemical_list: D008543:Melanins; D019999:Pharmaceutical Solutions; C081789:dopamine melanin