Is melanin a semiconductor: The mysteries of electrical conduction and melanin bioelectronics?

Meredith, P., Mostert, B., Gentle, I. R., Hanson, G., Tandy, K., Namdas, E., Pratt, F. and Powell, B. J. (2011). Is melanin a semiconductor: The mysteries of electrical conduction and melanin bioelectronics?. In: Abstracts. XXIst International Pigment Cell Conference (IPCC): "Skin and Other Pigment Cells: Bridging Clinical Medicine and Science". ipcc2011: International Pigment Cell Conference. Skin and Other Pigment Cells: Bridging Clinical Medicine and Science, Bordeaux, France, (780-780). 20-24 September 2011. doi:10.1111/j.1755-148X.2011.00885.x


Author Meredith, P.
Mostert, B.
Gentle, I. R.
Hanson, G.
Tandy, K.
Namdas, E.
Pratt, F.
Powell, B. J.
Title of paper Is melanin a semiconductor: The mysteries of electrical conduction and melanin bioelectronics?
Conference name ipcc2011: International Pigment Cell Conference. Skin and Other Pigment Cells: Bridging Clinical Medicine and Science
Conference location Bordeaux, France
Conference dates 20-24 September 2011
Convener European Society for Pigment Cell Research; Department of Dermatology and Pediatric Dermatology, University of Bordeaux
Proceedings title Abstracts. XXIst International Pigment Cell Conference (IPCC): "Skin and Other Pigment Cells: Bridging Clinical Medicine and Science"   Check publisher's open access policy
Journal name Pigment Cell and Melanoma Research   Check publisher's open access policy
Place of Publication Malden, MA, U.S.A.
Publisher Wiley-Blackwell Publishing
Publication Year 2011
Sub-type Published abstract
DOI 10.1111/j.1755-148X.2011.00885.x
ISSN 0893-5785
1755-148X
1755-1471
Volume 24
Issue 4
Start page 780
End page 780
Total pages 1
Language eng
Formatted Abstract/Summary
Melanins have been known to conduct and photo-conduct electricity for more than four decades. Renewed interest in melanins as advanced functional materials has emerged more recently, particularly in the context of a biological electrical interface material. Since the early 70’s the standard model for melanin in the solid-state has been as an amorphous semiconductor as per the Mott-Davis formalism. This assertion was derived primarily from observations of electrical switching between high and low resistive states. Indeed, it has been argued that melanin constituted the first demonstrated electrically active organic device and organic semiconductor. However, it is by no means clear that this is the appropriate or correct description and multiple observations of more exotic phenomena such as apparent ambipolar behavior and humidity dependent electrical conductivity have very much cast doubt on amorphous semiconductivity being the necessary and sufficient model. In our paper we will describe recent work focused on unraveling this difficult and seemingly intractable problem. We have used a combination of techniques including muon-spin relaxation (μSR), electron paramagnetic resonance and conductivity measurements and find that melanin has characteristics of a hybrid ion (proton)-electron conductor. Its electronic biophysics is dominated by ionic behavior and we show that this originates from the so-called comproportionation equilibrium whereby protons are released in a hydroquinone-to-quinone reaction. We also demonstrate how this exotic behavior can be used in an allsolid- state organic electrochemical transistor to affect ion-toelectron transduction – a key element in bioelectronic interfacing. A full understanding of melanin’s electrical properties will not only allow its potential as a bioelectronic material to be realized but could have major implications for advancing our knowledge of its biological role and function.
Q-Index Code EX
Q-Index Status Provisional Code
Institutional Status UQ
Additional Notes Presented during Session CS2: "Chemistry and biophysics of melanins" as Paper C7.

Document type: Conference Paper
Collections: School of Mathematics and Physics
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