Size-Dependent Local Ordering in Melanin Aggregates and Its Implication on Optical Properties

Träg J, Duchstein P, Hennemann M, Clark T, Guldi DM, Zahn D (2019)


Publication Type: Journal article

Publication year: 2019

Journal

DOI: 10.1021/acs.jpca.9b08722

Abstract

We present atomic scale models of differently sized eumelanin nanoaggregates from molecular dynamics simulations combined with a simulated annealing procedure. The analysis reveals the formation of secondary structures due to π-stacking on one hand, but on the other hand a broad distribution of stack geometries in terms of stack size, horizontal displacement angles, and relative torsion angles. The displacement angle distribution, which is a measure of the occurrence of zigzag and linear stacking motives, respectively, strongly depends on the aggregate size - and is hence controlled by the interplay of surface and bulk energy terms. Semiempirical spectra calculations of small stacks (up to five protomolecules) reveal a strong dependence on the precise stack structure and allow for a direct structure-property correlation. The observed spectral shifts result in an overall spectral broadening and, hence, further support the geometric disorder model, which complements the chemical disorder model in the interpretation of eumelanin's monotonically increasing broad-band absorption.

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How to cite

APA:

Träg, J., Duchstein, P., Hennemann, M., Clark, T., Guldi, D.M., & Zahn, D. (2019). Size-Dependent Local Ordering in Melanin Aggregates and Its Implication on Optical Properties. Journal of Physical Chemistry A. https://doi.org/10.1021/acs.jpca.9b08722

MLA:

Träg, Johannes, et al. "Size-Dependent Local Ordering in Melanin Aggregates and Its Implication on Optical Properties." Journal of Physical Chemistry A (2019).

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