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Brizuela Guerra N, Morais Lima JV, Nozella NL, Boratto MH, Paulin JV, Graeff CFDO. Electrochemical Doping Effect on the Conductivity of Melanin-Inspired Materials. ACS APPLIED BIO MATERIALS 2024; 7:2186-2196. [PMID: 38466818 DOI: 10.1021/acsabm.3c01166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/13/2024]
Abstract
Eumelanin is a natural pigment that can be particularly valuable for sustainable bioelectronic devices due to its inherent biocompatibility and hydration-dependent conductivity. However, the low conductivity of eumelanin limits its technological development. In this research, electrochemical doping was proposed as an alternative route to increase the electronic conductivity of synthetic eumelanin derivatives. Thin films of sulfonated eumelanin were deposited on platinum interdigitated electrodes and electrochemically treated by using cyclic voltammetry and chronoamperometry treatments. X-ray photoelectron spectroscopy analysis confirmed ion doping in sulfonated melanin. Current-voltage, current-time, and electrochemical impedance measurements were used to investigate the effect of different aqueous electrolytes (including KCl and LiClO4) treatments on the charge transport of sulfonated eumelanin. We show that the conductivity depends on the type and size of the anion used and can reach 10-3 S·cm-1. Additionally, depending on the electrolyte, there is a change in charge transport from mixed ionic/electronic to a predominantly electronic-only conduction. Our results show that the chemical nature of the ion plays an important role in the electrochemical doping and, consequently, in the charge transport of eumelanin. These insights serve as inspiration to explore the use of alternative electrolytes with different compositions further and develop eumelanin-based devices with tunable conductivities.
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Affiliation(s)
- Nayrim Brizuela Guerra
- Department of Physics and Meteorology, School of Sciences, São Paulo State University (UNESP), Bauru 17033-360, SP, Brazil
| | - João Victor Morais Lima
- Department of Physics and Meteorology, School of Sciences, São Paulo State University (UNESP), Bauru 17033-360, SP, Brazil
| | - Natan Luis Nozella
- Department of Physics and Meteorology, School of Sciences, São Paulo State University (UNESP), Bauru 17033-360, SP, Brazil
| | - Miguel Henrique Boratto
- Department of Physics and Meteorology, School of Sciences, São Paulo State University (UNESP), Bauru 17033-360, SP, Brazil
| | - João Vitor Paulin
- Department of Physics and Meteorology, School of Sciences, São Paulo State University (UNESP), Bauru 17033-360, SP, Brazil
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Al-Shamery N, Benselfelt T, Lee PS. Melanin and Polypyrrole-Coated Nanocellulose Hydrogel Networks for Environmental Sensing and Energy Storage. ACS APPLIED MATERIALS & INTERFACES 2023. [PMID: 37205839 DOI: 10.1021/acsami.3c03337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Melanins are black-brown pigments of a specific class of poly indolequinones found in nature and in the human body. They are responsible for photoprotection, radical scavenging, and metal ion chelation. Recently, there has been significant interest in eumelanin as a functional material due to its macromolecular structure and the exploitation of the quinone-hydroquinone redox equilibrium. While eumelanin can be used in many promising applications, it is insoluble in most solvents, limiting its processing into homogeneous materials and coatings. A promising approach is to use a carrier system to stabilize eumelanin by incorporating cellulose nanofibrils (CNFs), a nanoscopic material that originates from plant biomass. In this work, a flexible network consisting of CNFs coupled with vapor-phase polymerized conductive polypyrrole (PPy) is utilized to form a functional eumelanin hydrogel composite (MelaGel) for environmental sensing and battery applications. Flexible sensors for detecting pH or metal ions made from MelaGel can detect both pH values in a range from 4 to 10 and metal ions like zinc(II), copper(II), and iron(III), paving the way for environmental and biomedical sensor applications. The reduced internal resistance in the MelaGel leads to improved charge storage ability compared to synthetic eumelanin composite electrodes. Other noteworthy advantages of the MelaGel are the amphiphilic nature of PPy and the additionally offered redox centers. Lastly, this material was tested in aqueous electrolyte zinc coin cells, where it was shown to have charge/discharge stability for over 1200 cycles, showcasing this MelaGel composite as a promising eumelanin-based composite hybrid sensor/energy storage material.
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Affiliation(s)
- Noah Al-Shamery
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore, Singapore
| | - Tobias Benselfelt
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore, Singapore
| | - Pooi See Lee
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore, Singapore
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3
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Beilinson Y, Rassabina A, Lunev I, Faizullin D, Greenbaum A, Salnikov V, Zuev Y, Minibayeva F, Feldman Y. The dielectric response of hydrated water as a structural signature of nanoconfined lichen melanins. Phys Chem Chem Phys 2022; 24:22624-22633. [PMID: 36102934 DOI: 10.1039/d2cp01383e] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Lichens are unique symbiotic organisms from a mutually beneficial alliance of fungi and algae/cyanobacteria that successfully survive extreme temperatures and drought conditions. Most probably such extraordinary vitality of lichens is underlain by melanins, one of the main structural and chemical lichen components, and their mutual relationship with residual water. In this paper, we propose mechanisms, which allow lichens to store up the extra water in their structure. Melanins that are constituents of the cortical lichen layer and presumably contribute to unique water-lichen interactions are chosen for physical experiments in a wide temperature domain. Two melanin pigments extracted from different lichens are studied here - eumelanin from Lobaria pulmonaria and allomelanin from Cetraria islandica. To investigate the inner melanin structure and water-melanin interactions, FTIR and BDS techniques are applied. The BDS technique was used in a wide temperature region of 123-293 K for melanins with various hydration levels. The relaxation processes related to the confinement of supercooled water - in melanins are observed and discussed in details. At medium and high hydration levels, the relaxation process in two melanins of different chemical compositions and supramolecular structures exhibits a well-known crossover that was already observed in many types of confinements. The analysis of FTIR and BDS results helps to clarify the lichen-water interaction processes.
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Affiliation(s)
- Yael Beilinson
- Department of Applied Physics, Soft Condensed Matter Laboratory, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem, 9190401, Israel.
| | - Anna Rassabina
- Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of RAS, Lobachevsky str. 2/31, Kazan, 420111, Russian Federation.
| | - Ivan Lunev
- Kazan Federal University, Institute of Physics, Kremlevskaya str.18, Kazan, 420008, Russian Federation
| | - Dzhigangir Faizullin
- Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of RAS, Lobachevsky str. 2/31, Kazan, 420111, Russian Federation.
| | - Anna Greenbaum
- Department of Applied Physics, Soft Condensed Matter Laboratory, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem, 9190401, Israel. .,Racah Institute of Physics, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem, 9190401, Israel
| | - Vadim Salnikov
- Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of RAS, Lobachevsky str. 2/31, Kazan, 420111, Russian Federation.
| | - Yuriy Zuev
- Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of RAS, Lobachevsky str. 2/31, Kazan, 420111, Russian Federation.
| | - Farida Minibayeva
- Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of RAS, Lobachevsky str. 2/31, Kazan, 420111, Russian Federation.
| | - Yuri Feldman
- Department of Applied Physics, Soft Condensed Matter Laboratory, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem, 9190401, Israel.
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4
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Mostert AB. The importance of water content on the conductivity of biomaterials and bioelectronic devices. J Mater Chem B 2022; 10:7108-7121. [PMID: 35735112 DOI: 10.1039/d2tb00593j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Conductive biocompatible-, bioinspired- and biomaterials are increasing in importance, especially in bioelectronic applications where these materials are used in a variety of devices. Given the intended purpose of many of these devices is to interface with the human body, a pertinent issue is the effect of water from the environment on the electrical properties of the materials and devices. A researcher on biomaterials may currently not be aware, but the conductivity of these materials and device performances can be significantly altered with the presence of hydration in the environment. Examples will be given to highlight the problem that the conductivity of biomaterials can change by orders of magnitude depending on water content. Furthermore, case studies will be discussed in which control of the water content was key to understanding the underlying charge transport mechanism of conductive biomaterials. Examples of various devices and their response to hydration content will also be covered. Finally, this perspective will also mention the various methods of hydration control (including contrast studies) that can be used to perform careful work on conductive biomaterials and devices. Overall, water content should be considered an environmental variable as important as temperature to control for sound scientific investigation and to yield understanding of conductive biomaterials and bioelectronic devices.
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Affiliation(s)
- A Bernardus Mostert
- Department of Physics, Swansea University, Singleton Park, SA2, 8PP, Wales, UK.
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Bedran ZV, Zhukov SS, Abramov PA, Tyurenkov IO, Gorshunov BP, Mostert AB, Motovilov KA. Water-Activated Semiquinone Formation and Carboxylic Acid Dissociation in Melanin Revealed by Infrared Spectroscopy. Polymers (Basel) 2021; 13:4403. [PMID: 34960952 PMCID: PMC8705668 DOI: 10.3390/polym13244403] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Revised: 11/29/2021] [Accepted: 12/09/2021] [Indexed: 01/22/2023] Open
Abstract
Eumelanin is a widespread biomacromolecule pigment in the biosphere and has been widely investigated for numerous bioelectronics and energetic applications. Many of these applications depend on eumelanin's ability to conduct proton current at various levels of hydration. The origin of this behavior is connected to a comproportionation reaction between oxidized and reduced monomer moieties and water. A hydration-dependent FTIR spectroscopic study on eumelanin is presented herein, which allows for the first time tracking the comproportionation reaction via the gradual increase of the overall aromaticity of melanin monomers in the course of hydration. We identified spectral features associated with the presence of specific "one and a half" C𝌁O bonds, typical for o-semiquinones. Signatures of semiquinone monomers with internal hydrogen bonds and that carboxylic groups, in contrast to semiquinones, begin to dissociate at the very beginning of melanin hydration were indicated. As such, we suggest a modification to the common hydration-dependent conductivity mechanism and propose that the conductivity at low hydration is dominated by carboxylic acid protons, whereas higher hydration levels manifest semiquinone protons.
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Affiliation(s)
- Zakhar V. Bedran
- Center for Photonics and 2D Materials, Moscow Institute of Physics and Technology, Institute Lane 9, 141701 Dolgoprudny, Russia; (Z.V.B.); (S.S.Z.); (P.A.A.); (I.O.T.); (B.P.G.)
| | - Sergey S. Zhukov
- Center for Photonics and 2D Materials, Moscow Institute of Physics and Technology, Institute Lane 9, 141701 Dolgoprudny, Russia; (Z.V.B.); (S.S.Z.); (P.A.A.); (I.O.T.); (B.P.G.)
| | - Pavel A. Abramov
- Center for Photonics and 2D Materials, Moscow Institute of Physics and Technology, Institute Lane 9, 141701 Dolgoprudny, Russia; (Z.V.B.); (S.S.Z.); (P.A.A.); (I.O.T.); (B.P.G.)
| | - Ilya O. Tyurenkov
- Center for Photonics and 2D Materials, Moscow Institute of Physics and Technology, Institute Lane 9, 141701 Dolgoprudny, Russia; (Z.V.B.); (S.S.Z.); (P.A.A.); (I.O.T.); (B.P.G.)
| | - Boris P. Gorshunov
- Center for Photonics and 2D Materials, Moscow Institute of Physics and Technology, Institute Lane 9, 141701 Dolgoprudny, Russia; (Z.V.B.); (S.S.Z.); (P.A.A.); (I.O.T.); (B.P.G.)
| | - A. Bernardus Mostert
- Department of Chemistry, Swansea University, Singleton Park, Swansea SA2 8PP, UK;
| | - Konstantin A. Motovilov
- Center for Photonics and 2D Materials, Moscow Institute of Physics and Technology, Institute Lane 9, 141701 Dolgoprudny, Russia; (Z.V.B.); (S.S.Z.); (P.A.A.); (I.O.T.); (B.P.G.)
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Martinez-Gonzalez JA, Cavaye H, McGettrick JD, Meredith P, Motovilov KA, Mostert AB. Interfacial water morphology in hydrated melanin. SOFT MATTER 2021; 17:7940-7952. [PMID: 34378618 DOI: 10.1039/d1sm00777g] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
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.
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Affiliation(s)
- J A Martinez-Gonzalez
- ISIS Neutron and Muon Source, Rutherford Appleton Laboratory, Science and Technology Facilities Council, Didcot, OX11 0QX, UK
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7
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Understanding the way eumelanin works: A unique example of properties and skills driven by molecular heterogeneity. POLYMER 2021. [DOI: 10.1016/j.polymer.2021.123952] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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9
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Mostert AB. Melanin, the What, the Why and the How: An Introductory Review for Materials Scientists Interested in Flexible and Versatile Polymers. Polymers (Basel) 2021; 13:1670. [PMID: 34065580 PMCID: PMC8161012 DOI: 10.3390/polym13101670] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2021] [Revised: 05/18/2021] [Accepted: 05/18/2021] [Indexed: 01/13/2023] Open
Abstract
Today, western society is facing challenges to create new medical technologies to service an aging population as well as the ever-increasing e-waste of electronic devices and sensors. A key solution to these challenges will be the use of biomaterials and biomimetic systems. One material that has been receiving serious attention for its biomedical and device applications is eumelanin. Eumelanin, or commonly known as melanin, is nature's brown-black pigment and is a poly-indolequinone biopolymer, which possess unique physical and chemical properties for material applications. Presented here is a review, aimed at polymer and other materials scientists, to introduce eumelanin as a potential material for research. Covered here are the chemical and physical structures of melanin, an overview of its unique physical and chemical properties, as well as a wide array of applications, but with an emphasis on device and sensing applications. The review is then finished by introducing interested readers to novel synthetic protocols and post synthesis fabrication techniques to enable a starting point for polymer research in this intriguing and complex material.
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Affiliation(s)
- A Bernardus Mostert
- Department of Chemistry, Swansea University, Singleton Park, Wales SA2 8PP, UK
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10
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Galeb HA, Wilkinson EL, Stowell AF, Lin H, Murphy ST, Martin‐Hirsch PL, Mort RL, Taylor AM, Hardy JG. Melanins as Sustainable Resources for Advanced Biotechnological Applications. GLOBAL CHALLENGES (HOBOKEN, NJ) 2021; 5:2000102. [PMID: 33552556 PMCID: PMC7857133 DOI: 10.1002/gch2.202000102] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 11/04/2020] [Indexed: 05/17/2023]
Abstract
Melanins are a class of biopolymers that are widespread in nature and have diverse origins, chemical compositions, and functions. Their chemical, electrical, optical, and paramagnetic properties offer opportunities for applications in materials science, particularly for medical and technical uses. This review focuses on the application of analytical techniques to study melanins in multidisciplinary contexts with a view to their use as sustainable resources for advanced biotechnological applications, and how these may facilitate the achievement of the United Nations Sustainable Development Goals.
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Affiliation(s)
- Hanaa A. Galeb
- Department of ChemistryLancaster UniversityLancasterLA1 4YBUK
- Department of ChemistryScience and Arts CollegeRabigh CampusKing Abdulaziz UniversityJeddah21577Saudi Arabia
| | - Emma L. Wilkinson
- Department of Biomedical and Life SciencesLancaster UniversityLancasterLA1 4YGUK
| | - Alison F. Stowell
- Department of Organisation, Work and TechnologyLancaster University Management SchoolLancaster UniversityLancasterLA1 4YXUK
| | - Hungyen Lin
- Department of EngineeringLancaster UniversityLancasterLA1 4YWUK
| | - Samuel T. Murphy
- Department of EngineeringLancaster UniversityLancasterLA1 4YWUK
- Materials Science InstituteLancaster UniversityLancasterLA1 4YBUK
| | - Pierre L. Martin‐Hirsch
- Lancashire Teaching Hospitals NHS TrustRoyal Preston HospitalSharoe Green LanePrestonPR2 9HTUK
| | - Richard L. Mort
- Department of Biomedical and Life SciencesLancaster UniversityLancasterLA1 4YGUK
| | - Adam M. Taylor
- Lancaster Medical SchoolLancaster UniversityLancasterLA1 4YWUK
| | - John G. Hardy
- Department of ChemistryLancaster UniversityLancasterLA1 4YBUK
- Materials Science InstituteLancaster UniversityLancasterLA1 4YBUK
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11
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Paulin JV, Batagin-Neto A, Meredith P, Graeff CFO, Mostert AB. Shedding Light on the Free Radical Nature of Sulfonated Melanins. J Phys Chem B 2020; 124:10365-10373. [PMID: 33153262 DOI: 10.1021/acs.jpcb.0c08097] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Melanin, an important class of natural pigment found in the human body, has stood out as a promising bioelectronic material due to its rather unique collection of electrical properties and biocompatibility. Among the available melanin derivatives, the sulfonated form has proven to not only be able to produce homogeneous device quality thin films with excellent adhesion, even on hydrophobic surfaces, but also to act as an ion to electron transducing element. It has recently been shown that the transport physics (and dominant carrier generation) may be related to a semiquinone free radical species in these materials. Hence, a better understanding of the paramagnetic properties of sulfonated derivatives could shed light on their charge transport behavior and thus enable improvement in regard to use in bioelectronics. Motivated by this question, in this work, different sulfonated melanin derivatives were investigated by hydration-controlled, continuous-wave X-band electron paramagnetic resonance spectroscopy and electronic structure calculations. Our results show that sulfonated melanin behaves similarly to non-functionalized melanin, but demonstrates a less pronounced response to humidity vis-à-vis standard melanin. We thus speculate on the structural and charge transport behavior in light of these differences with a view to further engineering structure-property relationships.
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Affiliation(s)
- J V Paulin
- School of Sciences, Postgraduate Program in Science and Technology of Materials (POSMAT), São Paulo State University (UNESP), Bauru, Brazil.,Department of Physics, Swansea University, Singleton Park, Swansea SA2 8PP, United Kingdom
| | - A Batagin-Neto
- School of Sciences, Postgraduate Program in Science and Technology of Materials (POSMAT), São Paulo State University (UNESP), Bauru, Brazil.,São Paulo State University (UNESP), Campus of Itapeva, Itapeva, Brazil
| | - P Meredith
- Department of Physics, Swansea University, Singleton Park, Swansea SA2 8PP, United Kingdom.,School of Mathematics and Physics, University of Queensland, St. Lucia Campus, Brisbane, Queensland 4072, Australia
| | - C F O Graeff
- School of Sciences, Postgraduate Program in Science and Technology of Materials (POSMAT), São Paulo State University (UNESP), Bauru, Brazil.,School of Sciences, Department of Physics, São Paulo State University (UNESP), Bauru, Brazil
| | - A B Mostert
- Department of Chemistry, Swansea University, Singleton Park, Swansea SA2 8PP, United Kingdom
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12
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Mostert AB, Rienecker SB, Sheliakina M, Zierep P, Hanson GR, Harmer JR, Schenk G, Meredith P. Engineering proton conductivity in melanin using metal doping. J Mater Chem B 2020; 8:8050-8060. [DOI: 10.1039/d0tb01390k] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The proton conductivity in the model bioelectronic material melanin, is increased via a unique doping strategy utilising the chelation of the transition metal ion copper II. We also propose a potential mechanism for future such ionic studies.
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Affiliation(s)
| | | | | | - Paul Zierep
- Institut für Physikalische Chemie
- Albert-Ludwigs-Universität
- Freiburg
- Germany
| | - Graeme R. Hanson
- Centre of Advanced Imaging
- University of Queensland
- St. Lucia
- Australia
| | - Jeffrey R. Harmer
- Centre of Advanced Imaging
- University of Queensland
- St. Lucia
- Australia
| | - Gerhard Schenk
- School of Chemistry and Molecular Biosciences
- University of Queensland
- St. Lucia
- Australia
| | - Paul Meredith
- School of Mathematics and Physics
- University of Queensland
- St. Lucia
- Australia
- Department of Physics
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13
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Tian Z, Hwang W, Kim YJ. Mechanistic understanding of monovalent cation transport in eumelanin pigments. J Mater Chem B 2019; 7:6355-6361. [PMID: 31465076 DOI: 10.1039/c9tb01211g] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Recent research advances in charge-conducting materials have enabled the transformation of the naturally-occurring materials into crucial components in many technologies, including renewable energy storage devices or bioelectronics. Among various candidates, eumelanins are promising charge storage materials, exhibiting hybrid electronic ionic conductivity in a hydrated environment. The chemical and electrochemical properties of eumelanins are relatively well studied; however, the structure-property relationship is still elusive up to date. Herein, we reported the mesoscale structure of eumelanins and its impact on the charge transport. X-ray scattering suggests that eumelanin pigments exhibit the semi-crystalline structure with ordered d-spacings. These unique mesoscale structures further influence the charge transport mechanism with the cations of various sizes. Understanding the structures with consequent electrochemical properties suggest that eumelanins can further be tuned to serve as high-performance naturally-occurring charge storage materials.
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Affiliation(s)
- Zhen Tian
- Department of Chemical Engineering, University of New Hampshire, Durham, NH 03824, USA.
| | - Wonseok Hwang
- Department of Chemistry and Biochemistry, University of Maryland, College Park, College Park, MD 20740, USA
| | - Young Jo Kim
- Department of Chemical Engineering, University of New Hampshire, Durham, NH 03824, USA.
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