Spectral and aggregative properties of two oxazine dyes in aqueous solutions containing structure-breaking and multifunctional additives

Abstract

This study demonstrates the visible spectral data for two oxazine dyes, brilliant cresyl blue (BCB) and Nile blue (NB) in aqueous additive solutions as a function of the dye and additive concentrations at room temperature. The added organic additives were thiourea (TU) and two basic mono and di-amino compounds, i.e. diethanolamine (DEA) and aminoethyl ethanolamine (AEEA). The monomer and dimer spectra as well as dimerization constants (Kd) of the studied dyes in water with or without TU were determined and analyzed using DECOM Program. Due to the multiple properties of the additives (having various functional groups), different absorption characteristics were observed for these dyes in water with or without additives. A reduction of the dimerization parameters for the dyes in aqueous additive solutions was observed. The exciton theory was used to analyze the dimer structure. The nature of deprotonation of the dyes in the basic media (adjusted by addition of additive) was interpreted in terms of direct and indirect mechanisms of proton transfer process.