Molecular interactions between methylene blue and sodium alginate studied by molecular orbital calculations

Abstract

A methylene blue (MB) indicator embedded in sodium alginate (SA) film was previously examined for detecting active oxygen species. In a previous study, spectrometry was used to iden-tify and characterize the MB/SA complex. However, the decolorization mechanism was not fully assessed. In this study, our aim is to conduct computational calculations at the B3LYP/6‐31G(d) level to clarify the exact types and positions of the interaction that cause the decolorization in MB. The results demonstrate that MB/SA interacts with carboxylates (‐COO(superscript)‐(superscript)) of SA and the N, C, and S atoms of MB, confirming previous experimental observations.