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Full text release has been delayed at the author's request until August 17, 2026

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Chemical structure and optical functions of synthetic melanin

Li, Weiyao
http://orcid.org/0000-0002-8512-295X
http://rave.ohiolink.edu/etdc/view?acc_num=akron1627042724510547

Abstract Details

2021, Doctor of Philosophy, University of Akron, Polymer Science.
Melanin is a ubiquitous natural pigment that has a high refractive index (RI) and broad absorption across ultraviolet and visible wavelengths (200−700 nm). Even though melanin is known for its optical properties and absorption of light, we know very little about the chemistry and optical properties of these materials. Accordingly, we also know very little about how the structure and optical properties of melanin change after exposure to UV light. To address the questions on structure of melanin, we applied in-situ experiment with dynamic light scattering (DLS) and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-IR) to monitor the polydopamine synthesis in aqueous solution. Solid-state nuclear magnetic resonance (ssNMR) and FTIR has been used to understand the chemical structure of synthetic melanin (polydopamine and polydopa). Upon exposure to UV, we observe an increase in the aromatic components and some of the indole repeating units convert into furopyrrole structures, which also results in a release of CO2. We also observed the reduction in the aliphatic amine groups by using 15N ssNMR. In addition to the elucidation of the chemical structure of melanin, we have also used ellipsometry to measure changes in the complex RI in the visible and near IR wavelengths (360-1700 nm) after UV irradiation. Interestingly, both the real component of RI and absorption (imaginary component of refractive index) increase after UV absorption, indicating higher absorption efficiency of melanin after UV exposure. To exploit the change in complex RI of melanin after extremely high UV exposure, we have developed structural colors that do not fade upon UV exposure. Melanin is an important component in protecting us from UV radiation and has been an important material that produces structural color in nature. The observation of melanin being more effective after UV radiation may help in developing new materials to block UV radiation.
Ali Dhinojwala (Advisor)
Toshikazu Miyoshi (Committee Chair)
Abraham Joy (Committee Member)
Weinan Xu (Committee Member)
Chrys Wesdemiotis (Committee Member)
128 p.
Molecular Chemistry; Polymers

Recommended Citations

Citations

  • Li, W. (2021). Chemical structure and optical functions of synthetic melanin [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1627042724510547

    APA Style (7th edition)

  • Li, Weiyao. Chemical structure and optical functions of synthetic melanin. 2021. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1627042724510547.

    MLA Style (8th edition)

  • Li, Weiyao. "Chemical structure and optical functions of synthetic melanin." Doctoral dissertation, University of Akron, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron1627042724510547

    Chicago Manual of Style (17th edition)

akron1627042724510547
© 2021, all rights reserved.
This open access ETD is published by University of Akron and OhioLINK.