A strategy towards melanin-based functional material: rGO and sulfonated melanin composites

Melanin is a natural pigment and is one of the most promising materials in the emerging field of bioelectronics. The low conductivity of this class of materials is a limiting factor to their implementation in electronics. In this work, we have improved the electrical properties of a melanin-like material by combining it with reduced graphene oxide (rGO). Three different concentrations of rGO (5, 10 and 15 wt%) were studied. The composites were structurally (SEM, Raman, XPS, FTIR, and solid-state NMR) and optically (UV-vis and PL) characterized. The electrical properties were investigated through transient current, current-voltage curves and electrochemical impedance under different humidity levels. An improved DC conductivity was found for the 15%rGO@sulfonated melanin composite. The results suggest that, together with sulfonated melanin, it could potentially be suitable for applications in bioelectronics and/or organic electronics.