Synthesis and characterization of melanin in DMSO

Bronze‐Uhle, Erika S.; Batagin‐Neto, Augusto; Xavier, Pedro Henrique Petri; Fernandes, Nicole I.; Azevêdo, Eduardo Ribeiro de; Graeff, Carlos Frederico de Oliveira

doi:10.1016/j.molstruc.2013.04.061

Cited by 59 publications

(73 citation statements)

References 32 publications

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“…28 The effect of the processing solvent on the chemical composition of eumelanin lms has been poorly investigated. Our results suggest that the use of Dopa and Sigma melanin deposited from DMSO suspensions yields preferentially lms of a macromolecular material resembling the eumelanin pigment.…”

Section: Resultsmentioning

confidence: 99%

“…DMSO melanin has to be stored under inert atmosphere, since it is prone to a slow degradation in air, signicantly reducing its solubility. 28 Sigma melanin and all other chemicals were purchased from Sigma Aldrich and used as received. The eumelanins were suspended in DMSO or ammonia solution (2 : 1 by volume, NH 3(aq) (28%) in deionized water), stirred for 30 minutes, and ltered.…”

Section: Sample Preparationmentioning

confidence: 99%

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Eumelanin thin films: solution-processing, growth, and charge transport properties

et al. 2013

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Eumelanin pigments show hydration-dependent conductivity, broad-band UV-vis absorption, and chelation of metal ions. Solution-processing of synthetic eumelanins opens new possibilities for the characterization of eumelanin in thin film form and its integration into bioelectronic devices. We investigate the effect of different synthesis routes and processing solvents on the growth, the morphology, and the chemical composition of eumelanin thin films using atomic force microscopy and X-ray photoelectron spectroscopy. We further characterize the films by transient electrical current measurements obtained at 50% to 90% relative humidity, relevant for bioelectronic applications. We show that the use of dimethyl sulfoxide is preferable over ammonia solution as processing solvent, yielding homogeneous films with surface roughnesses below 0.5 nm and a chemical composition in agreement with the eumelanin molecular structure. These eumelanin films grow in a quasi layer-bylayer mode, each layer being composed of nanoaggregates, 1-2 nm high, 10-30 nm large. The transient electrical measurements using a planar two-electrode device suggest that there are two contributions to the current, electronic and ionic, the latter being increasingly dominant at higher hydration, and point to the importance of time-dependent electrical characterization of eumelanin films.

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Section: Resultsmentioning

confidence: 99%

Section: Sample Preparationmentioning

confidence: 99%

Eumelanin thin films: solution-processing, growth, and charge transport properties

et al. 2013

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“…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%

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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“…In the aliphatic region of the 1 H NMR spectra, signals in the range 0.8e1.0 ppm could be assigned to CH 3 groups of alkyl fragments, such as CH 2 CH 3 , CH(CH 3 ) 2 , which might come from residual protein; signals at 2.0 ppm belonged to methylene or the ester group (eOCOCH3) (24), indicating the existence of carboxylate structures. The broad peak in the absorption region around 3.5 ppm could be assigned to methyl (NeCH 3 ) bound to the 1st position of indole or pyrrole ring and eOCH 3 bound to the ring (25). The broadened signals centered at 6.5 and 7.3 ppm were aromatic hydrogens of indole or pyrrole ring, showing the various chemical environments around aromatic hydrogens and the diversity of connections among various groups in the melanin from C. molossus L. It was worth noting the signals of carboxyl protons were not detected due to the fact that C. molossus L. sample was mainly composed of DHI-eumelanin without carboxyl.…”

Section: Fourier Transform Infrared Spectroscopy Scanningmentioning

confidence: 99%

Preparation of melanin from Catharsius molossus L. and preliminary study on its chemical structure

Xin

Tan

et al. 2015

Journal of Bioscience and Bioengineering

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Synthesis and characterization of melanin in DMSO

Cited by 59 publications

References 32 publications

Eumelanin thin films: solution-processing, growth, and charge transport properties

Eumelanin thin films: solution-processing, growth, and charge transport properties

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

Preparation of melanin from Catharsius molossus L. and preliminary study on its chemical structure

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