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Decoupling Ionic and Electronic Currents in Melanin

Margarita Sheliakina, Bernard Mostert Orcid Logo, Paul Meredith Orcid Logo

Advanced Functional Materials, Volume: 28, Issue: 46, Start page: 1805514

Swansea University Authors: Bernard Mostert Orcid Logo, Paul Meredith Orcid Logo

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DOI (Published version): 10.1002/adfm.201805514

Abstract

Melanin, the human skin pigment, has emerged as a model material for bioelectronic interfaces due to its biocompatibility, ability to be processed into electronic‐device‐grade thin films, and transducing charge transport properties. These charge transport properties have been suggested to be of a mi...

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Published in: Advanced Functional Materials
ISSN: 1616-301X
Published: Wiley 2018
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URI: https://cronfa.swan.ac.uk/Record/cronfa44756
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Abstract: Melanin, the human skin pigment, has emerged as a model material for bioelectronic interfaces due to its biocompatibility, ability to be processed into electronic‐device‐grade thin films, and transducing charge transport properties. These charge transport properties have been suggested to be of a mixed protonic/electronic nature, regulated by a redox reaction that can be manipulated by changing the material's hydration state. However, to date, there are no detailed reports which clarify, quantify, or disentangle the protonic and electronic contributions to long‐range current conduction in melanin. Described herein, is a systematic hydration controlled electrical study on synthetic melanin thin films utilizing impedance/dielectric spectroscopy, which rationally investigates the protonic and electronic contributions. Through modeling and inspecting the frequency dependent behavior, it is shown that the hydration dependent charge transport is due to proton currents. Results show a real dielectric constant for hydrated melanin of order ≈1 × 103. Surprisingly, this very high value is maintained over a wide frequency range of ≈20–104 Hz. The electronic component appears to have little influence on melanin's hydration dependent conductivity: thus the material should be considered a protonic conductor, and not as previously suggested, a mixed protonic/electronic hybrid.
College: College of Science
Issue: 46
Start Page: 1805514