Understanding the Role of Aggregation in the Broad Absorption Bands of Eumelanin,ACS Nano

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Understanding the Role of Aggregation in the Broad Absorption Bands of Eumelanin
ACS Nano ( IF 15.8 ) Pub Date : 2018-11-30 00:00:00 , DOI: 10.1021/acsnano.8b04905
Kuk-Youn Ju ₁ , Martin C. Fischer _{1,

2} , Warren S. Warren _{1,

2,

3}

Affiliation

In this work, we investigate the relationship between the complex hierarchical assembly structure of eumelanin, its characteristic broad absorption band, and the highly unusual nonlinear dynamics revealed by pump–probe or transient absorption microscopy. Melanin-like nanoparticles (MelNPs), generated by spontaneous oxidation of dopamine, were created with uniform but adjustable size distributions, and kinetically controlled oxidation was probed with a wide range of characterization methods. This lets us explore the broad absorption bands of eumelanin models at different assembly levels, such as small subunit fractions (single monomeric and oligomeric units and small oligomer stacks), stacked oligomer fractions (protomolecules), and large-scale aggregates of protomolecules (parental particles). Both the absorption and pump–probe dynamics are very sensitive to these structural differences or to the size of intact particles (a surprising result for an organic polymer). We show that the geometric packing order of protomolecules in long-range aggregation is key secondary interactions to extend the absorption band of eumelanin to the low energy spectrum and produce drastic changes in the transient absorption spectrum.

中文翻译：

了解聚集在Eumelanin宽吸收带中的作用

在这项工作中，我们研究了Eumelanin复杂的分层装配结构，其特征性宽吸收带与泵浦探针或瞬态吸收显微镜揭示的高度异常的非线性动力学之间的关系。通过多巴胺的自发氧化生成的类黑色素纳米颗粒（MelNPs）具有均匀但可调节的尺寸分布，并通过多种表征方法探究了动力学控制的氧化。这使我们能够探索在不同组装水平上的Eumelanin模型的宽吸收带，例如小的亚基级分（单个单体和低聚物单元以及小的低聚物叠层），堆叠的低聚物级分（原分子）和原状分子的大规模聚集体（母体颗粒））。吸收动力学和泵浦动力学都对这些结构差异或完整颗粒的尺寸非常敏感（有机聚合物令人惊讶的结果）。我们表明，远距离聚集中的原分子的几何堆积顺序是关键的次级相互作用，以将洋红素的吸收谱带扩展至低能谱并在瞬态吸收谱中产生剧烈变化。

更新日期：2018-11-30

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