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

• Autor(a) principal: Paulin, J. V. [UNESP]
• Data de Publicação: 2021
• Outros Autores: Batagin-Neto, A. [UNESP], Naydenov, B., Lips, K., Graeff, C. F.O. [UNESP]
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional da UNESP
• Texto Completo: http://dx.doi.org/10.1039/d1ma00446h; http://hdl.handle.net/11449/229669

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. This journal is