Understanding The Role Of Aggregation In The Broad Absorption Bands Of Eumelanin.

Published

Journal Article

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 are key secondary interactions to extend the absorption band of eumelanin to the low energy spectrum, and produce drastic changes in the transient absorption spectrum.

Full Text

Duke Authors

Cited Authors

  • Ju, K-Y; Fischer, MC; Warren, WS

Published Date

  • November 30, 2018

Published In

PubMed ID

  • 30500158

Pubmed Central ID

  • 30500158

Electronic International Standard Serial Number (EISSN)

  • 1936-086X

International Standard Serial Number (ISSN)

  • 1936-0851

Digital Object Identifier (DOI)

  • 10.1021/acsnano.8b04905

Language

  • eng