A quantum yield map for synthetic eumelanin

Nighswander-Rempel, Stephen P.; Riesz, Jennifer; Gilmore, Joel; Meredith, Paul

doi:10.1063/1.2075147

Cited by 63 publications

(75 citation statements)

References 29 publications

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“…We observed that fluorescence behavior of the resulting PDA nanoparticles is very similar to eumelanin polymers in which the fluorescence spectrum is excitation wavelength dependent and can be tuned in the whole visible spectra. 28 With the increasing excitation wavelength, the emission maximum of the PDA nanoparticle solution shifts to the longer wavelengths (Figure 3b). Also, emission intensity is excitation wavelength dependent; it initially enhances with increasing wavelengths and then started to decrease gradually.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Turn-on Fluorescent Dopamine Sensing Based on in Situ Formation of Visible Light Emitting Polydopamine Nanoparticles

2014

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Dopamine is the principle biomarker for diseases such as schizophrenia, Huntington's, and Parkinson's, and the need is urgent for rapid and sensitive detection methods for diagnosis and monitoring of such diseases. In this Article, we report a turn-on fluorescent method for rapid dopamine sensing which is based on monitoring the intrinsic fluorescence of in situ synthesized polydopamine nanoparticles. The assay uses only a common base and an acid, NaOH and HCl to initiate and stop the polymerization reaction, respectively, which makes the assay extremely simple and low cost. First, we studied the in situ optical properties of polydopamine nanoparticles, for the first time, which formed under different alkaline conditions in order to determine optimum experimental parameters. Then, under optimized conditions we demonstrated high sensitivity (40 nM) and excellent selectivity of the assay. With its good analytical figures of merit, the described method is very promising for detection of dopamine related diseases. D opamine (DA), a catecholamine neurotransmitter, regulates many biological processes in central nervous, hormonal, and cardiovascular systems.1,2 Abnormal DA concentrations in biological fluids (e.g., urine, blood plasma, and extracellular fluid of the central nervous system) can be indicator of several diseases such as schizophrenia and Huntington's and Parkinson's diseases. 3−5 In this regard, sensitive and selective measurement of DA levels is important for diagnosis of these diseases and monitoring of patients. 6 Common DA detection methods utilize electrochemical analysis, 7−9 chromatography coupled with spectroscopy 10,11 (e.g., high-pressure liquid chromatography (HPLC)-fluorescence and gas chromatography/mass spectrometry (GC/MS)) and fluorescent 12−16 or colorimetric probes 1,17 (e.g., organic dyes, quantum dots, and gold nanoparticles). These methods, however, have some limitations. For instance, interference from uric acid (UA) and ascorbic acid (AA) largely limits selectivity of electrochemical methods. Chromatographic methods on the other hand, are time-consuming, labor intensive, and expensive with complicated procedures. Similarly, synthesis of fluorescent or colorimetric probes for DA detection involves complicated and time-consuming procedures.A straightforward, cost-effective and rapid alternative for DA detection is measuring the optical absorption of oxidation product of dopamine under alkaline conditions.18−22 These assays use only a common base (e.g., NaOH) or other oxidants (e.g., enzymes) as a reagent, and DA concentration is determined by simply measuring the optical absorption of the resulting brownish oxidation product. Unfortunately, the method demonstrates a poor sensitivity around a few micromolar. In these oxidation studies, the product is assumed as a quinone derivative of dopamine. 18 However, recent studies demonstrated that under alkaline conditions the quinone product is unstable and rapidly polymerized by covalent attachment and aggregation. 23−25 The resul...

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Section: ■ Results and Discussionmentioning

confidence: 99%

Turn-on Fluorescent Dopamine Sensing Based on in Situ Formation of Visible Light Emitting Polydopamine Nanoparticles

2014

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“…Illumination induces a photocurrent response which reaches a maximum value with a time constant of the order of seconds. Heating from strong nonradiative coupling of white light into the melanin samples 25,26 causes a reduction in water content and a subsequent increase in resistance-this effect is more pronounced at higher water content as expected from melanins' water binding capacity. 17,23 When the illumination is removed, the photocurrent dissipates with a time constant again of the order of a few seconds and finally a new (lower-due to the reduced water content) equilibrium dark conductivity is re-established.…”

Section: Applied Physics Letters 100 093701 (2012)mentioning

confidence: 98%

“…Specifically, it was argued by Crippa et al 14 that the negative conductivity was due to trap states in the photo-bandgap of melanin-a feature seen in amorphous semiconductors. The simpler explanation of heating induced water desorption emerges under careful environmental control and through a detailed knowledge of nonradiative conversion of absorbed photons, 25,26 and the adsorption, 23 and conductivity isotherms.…”

Section: Applied Physics Letters 100 093701 (2012)mentioning

confidence: 99%

On the origin of electrical conductivity in the bio-electronic material melanin

Mostert

Powell²,

Gentle³

et al. 2012

Applied Physics Letters

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“…17 Even more interesting, though, is that its quantum yield has been shown to have a similarly complex relationship. 21,22 These facts suggest that eumelanin is not a single chromophore but rather a collection of them, each with different electron-phonon coupling parameters. 16,23 Because pheomelanin is synthesized via a similar pathway to that of eumelanin, it could also be expected to exhibit similar structural and radiative properties.…”

Section: Introductionmentioning

confidence: 96%

Quantitative fluorescence spectra and quantum yield map of synthetic pheomelanin

2006

Biopolymers

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Spectroscopic studies of pheomelanin and its constituents have been sparse. These data present what is by far the most complete description of the fluorescence characteristics of synthetic pheomelanin. Emission spectra between 260 and 600 nm were acquired for excitation wavelengths between 250 and 500 nm at 1-nm intervals. A quantum yield map is also presented, correcting the fluorescence intensities for differences in species concentration and molar absorptivity. These fluorescence features exhibit interesting similarities and differences to eumelanin, and these data are interpreted with respect to possible chemical structures. Overall, these data suggest that pheomelanin oligomers may be more tightly coupled than those of eumelanin. Finally, the quantum yield is shown to be on the order of 10(-4) and exhibit a complex dependence on excitation energy, varying by a factor of 4 across the energies employed here.

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A quantum yield map for synthetic eumelanin

Cited by 63 publications

References 29 publications

Turn-on Fluorescent Dopamine Sensing Based on in Situ Formation of Visible Light Emitting Polydopamine Nanoparticles

Turn-on Fluorescent Dopamine Sensing Based on in Situ Formation of Visible Light Emitting Polydopamine Nanoparticles

On the origin of electrical conductivity in the bio-electronic material melanin

Quantitative fluorescence spectra and quantum yield map of synthetic pheomelanin

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