Abstract:
Being a family of biodegradable materials with natural origin, melanins are widely
used for development of model bioelectronic devices. However, the mechanism of their
electric conductivity is still a matter of discussions. Current study is devoted to the room
temperature impedance measurements of pure and copper-doped synthetic eumelanin at
different values of humidity in frequency range 0.1 - 5∙106 Hz. To analyze the obtained
impedance spectra, we utilize density relaxation times (DRT) methodology. The
performed analysis demonstrates an absence of significant difference in relaxation times
in the studied materials. At the lowest frequencies, the doped material has about 30 times
lower conductance than pure material. Possible origins of the observed phenomena are
discussed in terms of copper ions activity as complexing agent for water molecules and
semiquinone groups of melanin.