Dopamine-Melanin Nanofilms for Biomimetic Structural Coloration

• Published in: Biomacromolecules Vol. 16; no. 2; pp. 660 - 666
• Main Authors: Wu, Tong-Fei, Hong, Jong-Dal
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 09.02.2015
• Subjects: Biomimetic Materials - chemistry; Color; Melanins - chemistry; Nanotechnology - methods; Pharmaceutical Solutions - chemistry
• ISSN: 1525-7797; 1526-4602
• DOI: 10.1021/bm501773c

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.