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Role of semiconductivity and ion transport in the electrical conduction of melanin

A. B. Mostert, B. J. Powell, F. L. Pratt, G. R. Hanson, T. Sarna, I. R. Gentle, P. Meredith, Paul Meredith Orcid Logo, Bernard Mostert Orcid Logo

Proceedings of the National Academy of Sciences, Volume: 109, Issue: 23, Pages: 8943 - 8947

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

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DOI (Published version): 10.1073/pnas.1119948109

Abstract

Melanins are pigmentary macromolecules found throughout the biosphere that, in the 1970s, were discovered to conduct electricity and display bistable switching. Since then, it has been widely believed that melanins are naturally occurring amorphous organic semiconductors. Here, we report electrical...

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Published in: Proceedings of the National Academy of Sciences
ISSN: 0027-8424 1091-6490
Published: 2012
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URI: https://cronfa.swan.ac.uk/Record/cronfa38486
first_indexed 2018-02-09T14:22:18Z
last_indexed 2018-02-12T14:24:38Z
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spelling 2018-02-09T13:13:13.2994072 v2 38486 2018-02-09 Role of semiconductivity and ion transport in the electrical conduction of melanin 31e8fe57fa180d418afd48c3af280c2e 0000-0002-9049-7414 Paul Meredith Paul Meredith true false a353503c976a7338c7708a32e82f451f 0000-0002-9590-2124 Bernard Mostert Bernard Mostert true false 2018-02-09 BGPS Melanins are pigmentary macromolecules found throughout the biosphere that, in the 1970s, were discovered to conduct electricity and display bistable switching. Since then, it has been widely believed that melanins are naturally occurring amorphous organic semiconductors. Here, we report electrical conductivity, muon spin relaxation, and electron paramagnetic resonance measurements of melanin as the environmental humidity is varied. We show that hydration of melanin shifts the comproportionation equilibrium so as to dope electrons and protons into the system. This equilibrium defines the relative proportions of hydroxyquinone, semiquinone, and quinone species in the macromolecule. As such, the mechanism explains why melanin at neutral pH only conducts when “wet” and suggests that both carriers play a role in the conductivity. Understanding that melanin is an electronic-ionic hybrid conductor rather than an amorphous organic semiconductor opens exciting possibilities for bioelectronic applications such as ion-to-electron transduction given its biocompatibility. Journal Article Proceedings of the National Academy of Sciences 109 23 8943 8947 0027-8424 1091-6490 bioelectronics, electrical properties, biomacromolecules, ionic conduction 5 6 2012 2012-06-05 10.1073/pnas.1119948109 COLLEGE NANME Biosciences Geography and Physics School COLLEGE CODE BGPS Swansea University 2018-02-09T13:13:13.2994072 2018-02-09T13:13:13.3150109 Faculty of Science and Engineering School of Biosciences, Geography and Physics - Physics A. B. Mostert 1 B. J. Powell 2 F. L. Pratt 3 G. R. Hanson 4 T. Sarna 5 I. R. Gentle 6 P. Meredith 7 Paul Meredith 0000-0002-9049-7414 8 Bernard Mostert 0000-0002-9590-2124 9
title Role of semiconductivity and ion transport in the electrical conduction of melanin
spellingShingle Role of semiconductivity and ion transport in the electrical conduction of melanin
Paul Meredith
Bernard Mostert
title_short Role of semiconductivity and ion transport in the electrical conduction of melanin
title_full Role of semiconductivity and ion transport in the electrical conduction of melanin
title_fullStr Role of semiconductivity and ion transport in the electrical conduction of melanin
title_full_unstemmed Role of semiconductivity and ion transport in the electrical conduction of melanin
title_sort Role of semiconductivity and ion transport in the electrical conduction of melanin
author_id_str_mv 31e8fe57fa180d418afd48c3af280c2e
a353503c976a7338c7708a32e82f451f
author_id_fullname_str_mv 31e8fe57fa180d418afd48c3af280c2e_***_Paul Meredith
a353503c976a7338c7708a32e82f451f_***_Bernard Mostert
author Paul Meredith
Bernard Mostert
author2 A. B. Mostert
B. J. Powell
F. L. Pratt
G. R. Hanson
T. Sarna
I. R. Gentle
P. Meredith
Paul Meredith
Bernard Mostert
format Journal article
container_title Proceedings of the National Academy of Sciences
container_volume 109
container_issue 23
container_start_page 8943
publishDate 2012
institution Swansea University
issn 0027-8424
1091-6490
doi_str_mv 10.1073/pnas.1119948109
college_str Faculty of Science and Engineering
hierarchytype
hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Biosciences, Geography and Physics - Physics{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Biosciences, Geography and Physics - Physics
document_store_str 0
active_str 0
description Melanins are pigmentary macromolecules found throughout the biosphere that, in the 1970s, were discovered to conduct electricity and display bistable switching. Since then, it has been widely believed that melanins are naturally occurring amorphous organic semiconductors. Here, we report electrical conductivity, muon spin relaxation, and electron paramagnetic resonance measurements of melanin as the environmental humidity is varied. We show that hydration of melanin shifts the comproportionation equilibrium so as to dope electrons and protons into the system. This equilibrium defines the relative proportions of hydroxyquinone, semiquinone, and quinone species in the macromolecule. As such, the mechanism explains why melanin at neutral pH only conducts when “wet” and suggests that both carriers play a role in the conductivity. Understanding that melanin is an electronic-ionic hybrid conductor rather than an amorphous organic semiconductor opens exciting possibilities for bioelectronic applications such as ion-to-electron transduction given its biocompatibility.
published_date 2012-06-05T13:27:08Z
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score 11.080252

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