Gaseous Adsorption in Melanins: Hydrophilic Biomacromolecules with High Electrical Conductivities

A. Bernardus Mostert†, Karl J. P. Davy†, Jeremy L. Ruggles‡, Ben J. Powell†, Ian R. Gentle*‡ and Paul Meredith†
† Centre for Organic Photonics and Electronics, School of Mathematics and Physics
‡ School of Chemistry and Molecular Biosciences
The University of Queensland, Brisbane, Queensland 4072, Australia
Langmuir, 2010, 26 (1), pp 412–416
DOI: 10.1021/la901290f
Publication Date (Web): November 11, 2009
Copyright © 2009 American Chemical Society
*To whom correspondence should be addressed. E-mail: i.gentle@uq.edu.au.

Abstract

Abstract Image

The melanins are an important class of multifunctional biomacromolecules that possess a number of intriguing physical and chemical properties including electrical and photoconductivity. Unusually for a conducting organic material, eumelanin is hydrophilic and its electrical properties are strongly dependent on its hydration state. We have therefore measured adsorption isotherms for two polar adsorbates, water and ethanol, in the pressed powder pellets of synthetic eumelanin typically used in electrical studies. We show that a simple kinetic monolayer Langmuir model describes the adsorption and find that there are strong adsorbate−eumelanin interactions in both cases. These isotherms allow the proper scaling of electrical conductivity data and in doing so make progress toward a better understanding of eumelanin electrical properties, which is a critical prerequisite to the design of new eumelanin-like bioelectronic materials.

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History

  • Published In Issue January 05, 2010
  • Article ASAPNovember 11, 2009
  • Received: April 12, 2009
    Revised: September 11, 2009

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