Nonlinear Optical and Electro-optical Properties of Biopolymers

Kurtz, S. K.; Kozikowski, S. D.; Wolfram, L. J.

doi:10.1007/978-3-642-71907-3_10

Cited by 12 publications

(8 citation statements)

References 57 publications

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“…reported that isolated melanin free acid from sepia ink has a refractive index of 1.66 at the wavelength of 633 nm, which is lower than expected. [ 45 ] Xiao et al. directly measured the complex refractive index of polydopamine nanoparticles [ 28 ] and found a real part refractive index to be 1.74 at wavelength of 589 nm.…”

Section: Melanin Structure and Optical Propertiesmentioning

confidence: 99%

Bioinspired Melanin‐Based Optically Active Materials

Xiao

Shawkey

Dhinojwala

2020

Advanced Optical Materials

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the properties and functions of melanin, the synthesis of melanin-like nanoparticles, and its versatile applications in catalysis, energy, and biomedical fields. Over the last 5 years, more than 1000 papers on melanin have been published annually, based on data from the Web of Science. Quite a few of these papers have reviewed melanin's chemical structure, physiochemical properties, and biomedical applications. [4-6] However, a critical review focusing on optical functions of melanin is still lacking, despite tremendous emerging work on melaninbased photonic materials. The purpose of this review is to summarize current advances in bioinspired melanin-based optically active materials. Specifically, we will cover inherent optical properties of melanin, and then summarize melanin's optical functions in nature and its optics-related applications. 2. Melanin Structure and Optical Properties Melanin has complex chemical structures that is not yet fully understood, however, it does not hinder the exploration of their optical properties. In this section, we will first discuss classifications of melanin and then summarize unique optical properties of melanin, which will be important for both understanding its biological function in nature and synthetic applications. 2.1. Classification and Structure Conventionally, all black pigments are called melanin. Recently, d'Ischia et al. suggested that any phenolic polymers that have broadband light absorption, antioxidant, and intrinsic free radical character should be characterized as melanin. [5] Exact chemical structures of melanin remain elusive, mainly due to their insolubility in solvents, close binding with other cellular tissues, and an amorphous structure. Here, we do not elaborate on the complexities of melanin's chemical structures, [7] but rather focus on its classification. Melanin can be categorized as either natural or synthetic depending on whether it was synthesized in vivo or in vitro. Both have similar macroscopic properties, but their structures are likely quite different. Natural melanin, including eumelanin, pheomelanin, and neuromelanin, is produced from a series of enzymatic reactions starting from L-tyrosine in biological systems (Figure 1). [1] In cells (commonly melanocytes), the tyrosinase oxidizes L-tyrosine to dopaquinone (DQ). If cysteine concentration in Melanin is a widespread multifunctional biological pigment that has emerged as a promising platform for applications in coating, catalysis, energy, drug delivery, and medical therapy. Melanin is also a compelling material for photonic applications because of its favorable material characteristics, including broadband absorption, high refractive index, tunable fluorescence, and UV blocking capabilities. However, there is not yet a critical review focusing on optical functions of melanin. This review summarizes current advances in bioinspired melanin-based optically active materials, covering melanin's inherent optical properties and functions both in nature and in optics-related applications. It is ...

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Section: Melanin Structure and Optical Propertiesmentioning

confidence: 99%

Bioinspired Melanin‐Based Optically Active Materials

Xiao

Shawkey

Dhinojwala

2020

Advanced Optical Materials

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“…The dielectric constant for eumelanin (ǫ) has been measured to be ≈ 2.72 at optical frequencies (633nm) [37,38]. The dielectric constant for water (ǫ s ) is known to be ≈ 1.81 at optical frequencies [39,40].…”

Section: Prediction Of Scattering Coefficientmentioning

confidence: 99%

Quantitative Scattering of Melanin Solutions

Riesz

Gilmore

Meredith

2006

Biophysical Journal

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The optical scattering coefficient of a dilute, well-solubilized eumelanin solution has been accurately measured as a function of incident wavelength, and found to contribute <6% of the total optical attenuation between 210 and 325 nm. At longer wavelengths (325-800 nm), the scattering was less than the minimum sensitivity of our instrument. This indicates that ultraviolet and visible optical density spectra can be interpreted as true absorption with a high degree of confidence. The scattering coefficient versus wavelength was found to be consistent with Rayleigh theory for a particle radius of 38 +/- 1 nm. Our results shed important light on the role of melanins as photoprotectants.

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“…Melanin produced synthetically or isolated from biological systems is generally considered to be an amorphous heterogeneous biopolymer (Kurtz et al, 1986). Its inability to be crystallized, its strong optical absorptivity over the U V and visible range (Blois et al, 1964) and its chemical insolubility (Prota, 1988) have hampered attempts to elucidate its structure and hence to relate structure to function.…”

Section: Introductionmentioning

confidence: 99%

X‐Ray Characterization of Melanins—I

Cheng

Moss

Eisner

et al. 1994

Pigment Cell Research

132

128

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The intrinsic local structure characterization of natural sepia melanin and L-dopa and tyrosine synthetic melanin powder has been carried out by X-ray diffraction using synchrotron radiation. The derived structure factor, S(q), shows six significant diffuse peaks within the q-range from 0.3 A-1 to 16 A-1 in the reciprocal space (q = (4 pi sin theta)/lambda, 2 theta is the scattering angle). The Fourier transform of S(q), which yields the radial distribution function (RDF), gives us information in real space of a 1.42 A distance averaged over the C-C, C-O and C-N bond lengths as well as peaks at 2.40-2.41 A, 3.67-3.71 A and 4.67-4.70 A discrete neighbor distances. There is a great similarity in the scattering intensity profiles of the natural and synthetic melanins indicating that the synthetically prepared material may be essentially similar to "real" melanin in its local atomic arrangements. An evidence of a prepeak at q congruent to 0.45 A-1 has been confirmed which indicates a preferred length scale of approximately 13-20 A that corresponds to the initial particle size in colloidal melanin solutions.

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Nonlinear Optical and Electro-optical Properties of Biopolymers

Cited by 12 publications

References 57 publications

Bioinspired Melanin‐Based Optically Active Materials

Bioinspired Melanin‐Based Optically Active Materials

Quantitative Scattering of Melanin Solutions

X‐Ray Characterization of Melanins—I

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