UV-Visible study on the solubilization of solvatochromic-origin dyes in various micellar systems

Abstract

The evaluation of interactions between surfactants and dyes is an important challenge for a wide variety of scientific fields, contributing significantly to industrial development. Understanding the interactions between dyes of various classes and surfactants of different types can improve many processes in the future, such as enabling better capture of harmful dyes as industrial waste, thus facilitating their neutralization. In the pharmaceutical industry, there is a constant need to improve the design of new carriers for surfactant-stabilized drugs. Various dyes are very often successfully used as model molecules for therapeutic and/or diagnostic agents. In this regard, the present study evaluated the micellar solubilization of two dyes with different types of solvatochromism - Disperse Orange 3 and 2,6-dichloro-4-(2,4,6-triphenyl-1-pyridino)phenolate. A wide range of surfactants of different chemical natures - ionic (including cationic, anionic, and amphoteric) and nonionic ones - were used to form supramolecular micellar structures. Some shifts in the position of the absorption bands for ionic surfactants were observed, and the results suggest that they have a better ability for micellar solubilization, while having a higher solvatochromic behavior. The results were also compared with spectra for pure solvents allowing a broader determination of the resulting micellar aggregates’ polarity and indicating their place in the widely used ET(30) scale. Experimental studies indicate that both model molecules are not localized in the core, but are located in the more external part of the micelle. This approach allowed us to assess the solubilization of the dyes using each representative surfactant, thereby providing insights into their interaction with micellar systems. This comprehensive analysis allows for a more holistic understanding of the solubilization process and provides insights into the influence of surfactant charge on the solubilization efficiency. Moreover, the extended set of the surfactants as well as chromophores exhibiting different solvatochromic behavior takes account of our considerations and allows a deeper look at the solvatochromic phenomenon in the context of micelle-chromophore interactions.