Temperature-enhanced synthesis of DMSO-Melanin

Piacenti-Silva, Marina; Bronze‐Uhle, Erika S.; Paulin, João Vitor; Graeff, Carlos Frederico de Oliveira

doi:10.1016/j.molstruc.2013.10.041

Cited by 18 publications

(48 citation statements)

References 32 publications

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“…The band at 1771 cm −1 for Sigma melanin can be assigned to C = O stretching in carboxylic acid . The absence of such band for DMSO melanins can be related to the presence of the sulfonated groups . The mode at 1220 cm −1 is attributable to C − OH phenolic stretching and C − O stretching of carboxylic acid …”

Section: Resultsmentioning

confidence: 99%

“…DMSO melanin synthesized at room temperature (RT) and DMSO melanin synthesized at 100 °C were obtained as already reported in the literature …”

Section: Methodsmentioning

confidence: 99%

“…Recently, a method for in situ controlled deposition of melanin nanoparticles from the enzymatic reaction of l ‐3‐(3,4‐dihydroxyphenyl)‐alanine ( l ‐DOPA) with tyrosinase resulting in films with controlled growth and thickness has been reported . The oxidation of l ‐DOPA with benzoyl peroxide in dimethyl sulfoxide (DMSO) leads to the synthesis of DMSO melanin (Scheme ), with good solubility in DMSO, functional for the production of high quality films . Increasing the temperature during the synthesis of the DMSO melanin significantly increases the reaction rate and induces the decarboxylation of DHICA, thus increasing the number of positions available in the molecule for polymerization …”

Section: Introductionmentioning

confidence: 99%

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Novel insights on the physicochemical properties of eumelanins and their DMSO derivatives

Albano

Mauro

Kumar

et al. 2016

Polymer International

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The biopigment eumelanin, ubiquitous in flora and fauna, is made up of chemically heterogeneous macromolecules based on the 5,6‐dihydroxyindole and 5,6‐dihydroxyindole‐2‐carboxylic acid building blocks. The exciting possibility of designing eumelanin‐based technologies for bioelectronics and sustainable electronics has to be properly assessed by gaining insights on the charge transfer and charge carrier transport in the pigment, preferably in film form, easily amenable to devices. In this work, we report a study on the electrochemical behaviour of films of eumelanin and its derivatives synthesized in dimethyl sulfoxide (DMSO eumelanins) in different aqueous electrolytes, with different chemical compositions and pH. DMSO eumelanins feature an improved solubility in the solvent DMSO, of relevance for processing purposes. The voltammetric currents are higher at relatively low pH (5.5), as expected considering the well‐established proton transport properties of the biopigment. Raman spectroscopy and atomic force microscopy performed on eumelanin films were combined with thermogravimetry with the aim of advancing knowledge on the molecular and supramolecular features of synthetic commercially available eumelanin, DMSO eumelanins as well as natural eumelanin (Sepia melanin). The results collected permit unprecedented insights on the physicochemical properties of eumelanin. © 2016 Society of Chemical Industry

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Section: Resultsmentioning

confidence: 99%

“…DMSO melanin synthesized at room temperature (RT) and DMSO melanin synthesized at 100 °C were obtained as already reported in the literature …”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Novel insights on the physicochemical properties of eumelanins and their DMSO derivatives

Albano

Mauro

Kumar

et al. 2016

Polymer International

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“…Absorption spectra from 250 to 800 nm were recorded at regular time intervals using a quartz cuvette of 1 cm path length, until the reaction ended. The criteria for defining the reaction end have been discussed elsewhere . The size and surface charge of melanin particles were measured with a Delsa™ Nano (Beckman Coulter) instrument using a 0.007 mg mL −1 solution in Milli‐Q water.…”

Section: Methodsmentioning

confidence: 99%

Melanin synthesis under oxygen pressure

Bronze‐Uhle

Paulin

Piacenti-Silva

et al. 2016

Polymer International

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Melanins are promising materials for organic bioelectronics devices like transistors, sensors and batteries. In this study, the chemical structural changes of melanin synthesized, by the auto oxidation of L-DOPA, are analyzed for a new synthetic procedure that uses oxygen under pressure (4 to 8 atm). TEM, DLS, FTIR, NMR and XPS are use to characterize the material. Under oxygen pressure, melanin synthesis is accelerated, the polymer obtained is found to have structural differences most notably a higher number of carbonyl groups and different surface charges compared to conventional synthetic melanin. As a consequence it has higher homogeneity and it is soluble in water. To explain these findings a reaction mechanism is proposed based on current melanogenesis models.Keywords: Melanin, oxygen pressure, solubility, accelerated synthesis. E-mail address: joaovp281@gmail.comThis article is protected by copyright. All rights reserved.This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1002/pi.5185 Accepted Articleexample, thin films of synthetic melanin with good adherence and controllable thickness were made using layer-by-layer technique. It has also been reported that it is possible to obtain melanin films from electrochemical deposition methods, [8] An alternative to obtain good quality films is to modify the melanin structure preserving its main properties, but increasing its solubility or changing its aggregation state. The advantage of this approach is that all processing techniques used up to now for organic semiconducting polymers device production would be available for melanin. In addition, many routine advanced techniques dedicated to thin film or solution characterization could be used. In the last 15 years soluble melanin derivatives were synthesized using different functionalized groups. [14][15][16][17][18] In this study, we propose an alternative synthetic approach for a soluble melanin without any exotic functionalization using molecular oxygen under pressure. Molecular oxygen is considered an ideal oxidant in the context of "green chemistry"; it has low cost, is abundant and environmentally friendly, having thus academic and industrial interest. In addition the synthesis is found to be faster under oxygen pressure. EXPERIMENTALAll the commercially available chemicals were purchased from Acros or Sigma-Aldrich and were used without further purification. In what concerns reproducibility, more than 3 different syntheses were performed and similar optical and structural properties were obtained. Melanin synthesisThe synthesis of melanin was carried out using well-known procedures briefly described. [19] Initially 0.3 g of L-3,4-dihydroxyphenylalanine (L-DOPA) was dissolved in 60 mL of deionized water (Milli-Q), next 0.4 mL of ammonium hydroxide (NH 4 OH) is added, ...

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“…The aging process or the addition of NaOH or H 2 O will lead to the release of the sulfonate groups. Increasing temperature causes a decarboxylation of sulfonated DHI and facilitates the polymerization of sulfonated‐DHI …”

Section: The Modulation Of Melanin‐like Materialsmentioning

confidence: 99%