Supramolecular clusters clarification in ethanol-water mixture by using fluorescence spectroscopy and 2D correlation analysis

Due to the importance of ethanol-water solutions in many fields the different supramolecular clusters involved in this binary system is studied in detail by using fluorescence spectroscopy, at different concentration and incubation time after mixing. Two-dimensional (2D) correlation analysis is performed on the concentration-dependent mixtures (10-10 0%) at each incubation time, which find that the correlation intensity of emission peak at 330 nm for (H2O)(m)(EtOH)(n) not only related to the concentration but also gradually increase with the incubation time. Such results indicate that the cluster of (H2O)(m)(EtOH)(n) is the most stable one because it tends to be formed with longer incubation time. In addition, the correlation results indicate that at low concentration range of 10-45%, the dominated cluster is (H2O)(m)(EtOH) corresponding to a peak at 373 nm; while at high concentration range of 80-100%, the main cluster is (H2O)x(EtOH)(n) corresponding to an emission peak at 308 nm; however, the most stable cluster of (H2O)(m)(EtOH)(n), corresponding to the peak at 330 nm, not only predominate at the concentration range of 50-75% but also exist in all mixture at longer incubation time. Therefore, the present study provides a new approach to clarify the different supramolecular clusters in ethanol-water mixtures, which would be applied to other binary solution system. (C) 2020 Elsevier B.V. All rights reserved.