Eumelanin broadband absorption develops from aggregation-modulated chromophore interactions under structural and redox control

60Citations
Citations of this article
100Readers
Mendeley users who have this article in their library.

This article is free to access.

Abstract

Eumelanins, the chief photoprotective pigments in man and mammals, owe their black color to an unusual broadband absorption spectrum whose origin is still a conundrum. Excitonic effects from the interplay of geometric order and disorder in 5,6-dihydroxyindole (DHI)-based oligomeric/polymeric structures play a central role, however the contributions of structural (scaffold-controlled) and redox ( €-electron-controlled) disorder have remained uncharted. Herein, we report an integrated experimental-theoretical entry to eumelanin chromophore dynamics based on poly(vinyl alcohol)-controlled polymerization of a large set of 5,6-dihydroxyindoles and related dimers. The results a) uncover the impact of the structural scaffold on eumelanin optical properties, disproving the widespread assumption of a universal monotonic chromophore; b) delineate eumelanin chromophore buildup as a three-step dynamic process involving the rapid generation of oxidized oligomers, termed melanochromes (phase I), followed by a slow oxidant-independent band broadening (phase II) leading eventually to scattering (phase III); c) point to a slow reorganization-stabilization of melanochromes via intermolecular redox interactions as the main determinant of visible broadband absorption.

Cite

CITATION STYLE

APA

Micillo, R., Panzella, L., Iacomino, M., Prampolini, G., Cacelli, I., Ferretti, A., … D’Ischia, M. (2017). Eumelanin broadband absorption develops from aggregation-modulated chromophore interactions under structural and redox control. Scientific Reports, 7. https://doi.org/10.1038/srep41532

Register to see more suggestions

Mendeley helps you to discover research relevant for your work.

Already have an account?

Save time finding and organizing research with Mendeley

Sign up for free