Semiconductor Physics, Quantum Electronics & Optoelectronics, 21 (1), P. 95-99 (2018).

Nonmonotonic (in concentration) conductivity of aqueous solutions of fungal melanin
O.V. Kovalchuk1,2, T.M. Kovalchuk3

1Institute of Physics, NAS of Ukraine, 41, prospect Nauky, 03680 Kyiv, Ukraine
2Kyiv National University of Technologies and Design, 2, Nemirovich-Danchenko str., 01011 Kyiv, Ukraine
3V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine, 41, prospect Nauky, 03680 Kyiv, Ukraine

Abstract. The conductivity of aqueous (distilled and natural water) solutions of fungal melanin (purified and non-purified) has been studied. It has been shown that, in the presence of impurities, the conductivity of solution increases (for the concentration 0.1 wt% about an order of magnitude). On the concentration dependences of the melanin conductivity within the range of 0.0001 to 1 wt.% at least three particular sections have been detected. It was suggested that the presence of such sections is caused by three types of aggregation of melanin molecules: aggregation of several (mostly oppositely charged) molecules under the lowest melanin concentration, formation of nanoscale melanin clusters for the concentration of 0.002 to 0.06 wt.% and formation of micelles, when the melanin concentration is higher than 0.1 wt.%.

Keywords: melanin, conductivity, concentration, aqueous solutions.

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