High-field/high-frequency EPR spectroscopy on synthetic melanin: on the origin of carbon-centered radicals

Author(s)

Paulin, J. V. ^[1] ; Batagin-Neto, A. ^{[2, 1]} ; Naydenov, B. ^[3] ; Lips, K. ^{[4, 3, 5]} ; Graeff, C. F. O. ^{[6, 1]}

Affiliation

^[1] Sao Paulo State Univ UNESP, Sch Sci, Postgrad Program Sci & Technol Mat POSMAT, Bauru, SP - Brazil

^[2] Sao Paulo State Univ UNESP, Campus Itapeva, Itapeva - Brazil

^[3] Helmholtz Zentrum Berlin Mat & Energie GmbH, Berlin - Germany

^[4] Univ Utah, Dept Phys & Astron, Salt Lake City, UT - USA

^[5] Free Univ Berlin, Dept Phys, Berlin - Germany

^[6] Sao Paulo State Univ UNESP, Sch Sci, Dept Phys, Bauru, SP - Brazil

• Document type: Journal article
• Source: MATERIALS ADVANCES; JUL 2021.
• Web of Science Citations: 0

Abstract

Among all the pigments found in nature, melanin has drawn considerable attention for bioelectronics applications as it contains a set of physicochemical properties such as antioxidant activity, metal chelation, biocompatibility, broad-band absorbance throughout the UV-visible region, hydration-dependent conductivity and intrinsic and extrinsic free radical character. A better understanding of these properties is a matter of significant importance to improve melanin-based organic devices efficiently. Therefore, the origin of melanin free-radicals was studied using continuous-wave electron paramagnetic resonance (EPR) spectroscopy at 263 GHz for standard non-functionalized and sulfonated derivatives. Our results indicated that more than one radical species should be evoked to study the free-radical nature of standard and sulfonated melanin. Additionally, we also confirm that the free-radical system of sulfonated melanin is similar to non-functionalized melanin. Based on the g-anisotropy analysis, we propose which potential units could be responsible for carbon-centered radicals. (AU)

• FAPESP's process: 13/07296-2 - CDMF - Center for the Development of Functional Materials
• Grantee: Elson Longo da Silva
• Support Opportunities: Research Grants - Research, Innovation and Dissemination Centers - RIDC
• FAPESP's process: 12/03116-7 - Simulation of electronic and optical properties of organic materials
• Grantee: Augusto Batagin Neto
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 15/23000-1 - Vertical organic field-effect transistor using dyes of natural origin as active layer
• Grantee: João Vitor Paulin
• Support Opportunities: Scholarships in Brazil - Doctorate