Copper binding, tautomeric equilibrium, and thermal dehydration in eumelanins

Abstract

This work examines how copper ions affect the chemical state and thermal dehydration of synthetic eumelanin. XPS data indicate that copper doping shifts the tautomeric balance of oxidized indole units toward quinone-like forms, while temperature-dependent mid-IR spectroscopy reveals distinct contributions from weakly and strongly bound water. The results show that copper increases water uptake mainly through coordination-bound water, which does not form an efficient proton-transport network. These findings clarify why copper doping can increase hydration while reducing charge mobility in eumelanin-based materials.

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References

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