In-Depth Analysis of the Paramagnetic Properties in DHI/DHICA-Controlled Eumelanin

Eumelanin, a naturally occurring pigment derived from the oxidative polymerization of 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA), has been extensively studied for its role in human biology and its potential applications in biomedical and sustainable electronic fields. By employing X-band electron paramagnetic resonance spectroscopy, this study focuses on eumelanin with different DHI/DHICA ratios, directly comparing monomeric and polymeric forms. The analysis reveals significant differences in the paramagnetic profiles, with changes in spin dynamics and relaxation times closely linked to the distinct macrostructures formed during polymerization. These findings offer valuable insights into how the molecular architecture of eumelanin influences its paramagnetic environments.