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

Abstract

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, the What, the Why and the How: An Introductory Review for Materials Scientists Interested in Flexible and Versatile Polymers

“…The Graeff group have also pioneered other methods of synthesis, again to enable the ease of processing for materials applications. They have synthesized the above Dmelanin under O 2 pressure, creating a polymer with a greater carboxylated content and improving the reaction rate [160]. This idea of synthesizing melanin under O 2 pressure has also been applied to melanin synthesis in water [161].…”

High-field/high-frequency EPR spectroscopy on synthetic melanin: on the origin of carbon-centered radicals

“…Sulfonated-functionalized melanin derivative (SMel) was obtained through the oxidation of 1.50 g of DL-DOPA in 200 mL of DMSO (PA, Vetec, 99.9%) with 0.93 g of benzoyl peroxide (Vetec, 75.0-80.0 %). 57,59 The mixture was kept under magnetic stirring for 58 days at room temperature (T ≈ 300 K). Next, the solution was heated at 413 K to evaporate ¾ of the solvent and then mixed in acetonitrile (Synth, 99.5%) for two days.…”

“…The presence of Ndef + species may not be common; however, they arise from synthetic defect-like structures 26 and is usually seen in the fitting of N1s XPS spectra. 57,58,68,69 The g-values (g xx , g yy and g zz ) were estimated with the aid of Orca 3.0.3 computational package, 70 in a DFT/B3LYP/6-31G(d,p) approach.…”

“…Sulfonated melanin, whose basic structure is shown in Figure 1(b), behaves closely to standard melanin at X-band CW EPR 38 and has promising properties for bioelectronics applications. 17,[54][55][56][57] The experimental results were interpreted with spectral simulations and density functional theory, throwing light on the g-anisotropy of melanin-based radicals and their possible origin.…”

Formation of TiO2 nanostructures modified Eumelanin films with enhanced properties for biopolymer implementations

“…In the case of thin films of organic species such as melanin and its blend with TiO 2 anatase phase over the ITO conductive (Fig. 6b) layer, electron and hole scavengers and the charge recombination mechanism in the visible and up to near infrared region are dominant [26,37,38].…”