Singla Saranshu, Yang Zepeng, Patil Anvay, Guo Hao, Vanthournout Bram, Htut K Zin, Shawkey Matthew D, Tsige Mesfin, Dhinojwala Ali
School of Polymer Science and Engineering, The University of Akron, Akron, Ohio 44325, United States.
Department of Biology, The University of Ghent, 9000 Ghent, Belgium.
ACS Appl Mater Interfaces. 2023 Sep 27;15(38):45229-45238. doi: 10.1021/acsami.3c08152. Epub 2023 Sep 12.
Hollow melanosomes found in iridescent bird feathers, including violet-backed starlings and wild turkeys, enable the generation of diverse structural colors. It has been postulated that the high refractive index (RI) contrast between melanin (1.74) and air (1.0) results in brighter and more saturated colors. This has led to several studies that have synthesized hollow synthetic melanin nanoparticles and fabricated colloidal nanostructures to produce synthetic structural colors. However, these studies use hollow nanoparticles with thin shells (<20 nm), even though shell thicknesses as high as 100 nm have been observed in natural melanosomes. Here, we combine experimental and computational approaches to examine the influence of the varying polydopamine (PDA, synthetic melanin) shell thickness (0-100 nm) and core material on structural colors. Experimentally, a concomitant change in overall particle size and RI contrast makes it difficult to interpret the effect of a hollow or solid core on color. Thus, we utilize finite-difference time-domain (FDTD) simulations to uncover the effect of shell thickness and core on structural colors. Our FDTD results highlight that hollow particles with thin shells have substantially higher saturation than same-sized solid and core-shell particles. These results would benefit a wide range of applications including paints, coatings, and cosmetics.
在包括紫背椋鸟和野火鸡在内的具有虹彩的鸟类羽毛中发现的中空黑素体能够产生多种结构色。据推测，黑色素（1.74）与空气（1.0）之间的高折射率（RI）对比度导致了更明亮、更饱和的颜色。这引发了多项研究，这些研究合成了中空的合成黑色素纳米颗粒，并制造了胶体纳米结构以产生合成结构色。然而，这些研究使用的是壳层较薄（<20纳米）的中空纳米颗粒，尽管在天然黑素体中观察到壳层厚度高达100纳米。在这里，我们结合实验和计算方法来研究不同聚多巴胺（PDA，合成黑色素）壳层厚度（0 - 100纳米）和核心材料对结构色的影响。在实验中，总体粒径和RI对比度的同时变化使得难以解释中空或实心核心对颜色的影响。因此，我们利用时域有限差分（FDTD）模拟来揭示壳层厚度和核心对结构色的影响。我们的FDTD结果突出表明，具有薄壳的中空颗粒比相同尺寸的实心颗粒和核壳颗粒具有更高的饱和度。这些结果将有利于包括油漆、涂料和化妆品在内的广泛应用。
