Structural analysis and spectroscopic characterization of melanin-alginate films

• We present the optical, chemical, and structural analysis of alginate films with different melanin content. • Intermolecular interactions between alginate-glycerol and melanin induce a slight change in the structure of alginate. • UV–vis absorption increases with melanin content and the maximum slightly shifts to higher wavelengths. In the THz band, the refractive index increases with melanin concentration. Changes in the absorption coefficient are significant for higher frequencies. • The analysis suggests the potential use of melanin-alginate films as a viable environment for the examination of non-dissolved melanin. In this work, we present the spectroscopic and structural analysis of synthetic melanin incorporated within alginate films. We propose a synthesis methodology for alginate films with different concentrations of melanin. For this, Ca2 + -crosslinked alginate films plasticized with glycerol (30% w/w) are used as a matrix to support melanin in a non-disolved state. The structural and morphological characteristics of the alginate-melanin films are evaluated. Furthermore, we analyze the structural and morphological characteristics of the obtained films and analyze their spectroscopic characteristics from the ultraviolet to the terahertz bands of the electromagnetic spectrum. This work demonstrates that alginate films are a viable option as a matrix for the analysis and characterization of non-dissolved melanin. Moreover, we determine the dependence of the analyzed physical and optical properties of the alginate-melanin films with respect to the melanin concentration and discuss the relevance of the observed changes. The analysis suggests the potential use of melanin-alginate films for further examination of non-dissolved melanin.