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Interfacial water morphology in hydrated melanin

J. A. Martinez-Gonzalez, H. Cavaye, James McGettrick Orcid Logo, Paul Meredith Orcid Logo, K. A. Motovilov, Bernard Mostert Orcid Logo

Soft Matter, Volume: 17, Issue: 34, Pages: 7940 - 7952

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

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DOI (Published version): 10.1039/d1sm00777g

Abstract

The importance of electrically functional biomaterials is increasing as researchers explore ways to utilise them in novel sensing capacities. It has been recognised that for many of these materials the state of hydration is a key parameter that can heavily affect the conductivity, particularly those...

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Published in: Soft Matter
ISSN: 1744-683X 1744-6848
Published: Royal Society of Chemistry (RSC) 2021
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URI: https://cronfa.swan.ac.uk/Record/cronfa58097
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Abstract: The importance of electrically functional biomaterials is increasing as researchers explore ways to utilise them in novel sensing capacities. It has been recognised that for many of these materials the state of hydration is a key parameter that can heavily affect the conductivity, particularly those that rely upon ionic or proton transport as a key mechanism. However, thus far little attention has been paid to the nature of the water morphology in the hydrated state and the concomitant ionic conductivity. Presented here is an inelastic neutron scattering (INS) experiment on hydrated eumelanin, a model bioelectronic material, in order to investigate its ‘water morphology’. We develop a rigorous new methodology for performing hydration dependent INS experiments. We also model the eumelanin dry spectra with a minimalist approach whereas for higher hydration levels we are able to obtain difference spectra to extract out the water scattering signal. A key result is that the physi-sorbed water structure within eumelanin is dominated by interfacial water with the number of water layers between 3–5, and no bulk water. We also detect for the first time, the potential signatures for proton cations, most likely the Zundel ion, within a biopolymer/water system. These new signatures may be general for soft proton ionomer systems, if the systems are comprised of only interfacial water within their structure. The nature of the water morphology opens up new questions about the potential ionic charge transport mechanisms within hydrated bioelectronics materials.
College: Faculty of Science and Engineering
Funders: J. A. M-G. acknowledge funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 665593 awarded to the Science and Technology Facilities Council. J. D. McG thank the EPSRC SPECIFIC project for funding (EP/N020863/1) & WEFO (ERDF) project AIM (80708 & EP/M015254/2) for their ongoing support for XPS maintenance. P. M. is a Seˆr Cymru II National Research Chair, which is supported by the Welsh Government through the European Regional Development Fund. K. A. M. acknowledge funding from Russian Science Foundation under grant 19-73-10154. A. B. M. is a Seˆr Cymru II fellow and the results incorporated in this work is supported by the Welsh Government through the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska Curie grant agreement no. 663830.
Issue: 34
Start Page: 7940
End Page: 7952

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