Structural and optical properties of soluble melanin analogues with enhanced photoluminescence quantum efficiency

Melanin is a functional material of growing interest for bioelectronics. Several melanin analogues have been employed in order to fully explore its potential; in this work melanin was synthesized using dimethylsulfoxide (DMSO) and O2 under pressure as oxidizing agent. It is shown that the products have similar functional groups and solubility; however, O2 pressure produces more carboxylated structures and improves the synthesis reaction rate. The photoluminescence of all sulfonated melanin analogues was studied. It is shown that the material synthesized in DMSO has photoluminescence in the visible region (487 nm) with a quantum yield of (2.12 ± 0.02)%. This good quantum yield compared to natural and synthetic melanin may open new perspectives for its use in optoelectronics applications. The origin of this effect is discussed in terms of the polymer structure. © 2018 Society of Chemical Industry Melanin is synthesized using dimethylsulfoxide and O2 pressure. Sulfonated monomers are obtained with higher content of carboxylated structure, solubility in three organic solvent and enhanced photoluminescence in the visible region.