Colorimetric Revealing of Ethanol–Water Cluster (E-Wc) Transitions in Binary Solution Based on Starch–I2 Crystallization

作者：Hui-Shuang Li, Hao-Jie Bai, Hongwei Li, Yuqing Wu · 发表于：Molecules · 年份：2025 · DOI：10.3390/molecules30183785 · 研究领域：Analytical Chemistry and Chromatography、Thermodynamic properties of mixtures、Isotope Analysis in Ecology

We have developed a highly sensitive colorimetric probe based on starch–iodine (I2) crystallization for the precise discrimination of ethanol–water clusters (E-Wc) within binary ethanol–water solutions (E-Ws). This probe enables the identification of specific E-Wc species and their corresponding transition points. Notably, two distinct transition points were identified at ethanol volume fractions of 40–45% and 75–77%. The former corresponds to the structural transition from (H2O)m(EtOH) to (H2O)m(EtOH)n, characterized by a significant loss of blue coloration, while the latter signifies the transition from (H2O)m(EtOH)n to (H2O)(EtOH)n, as evidenced by alterations in the absorption intensity of the starch–I2 complex. Mechanistic studies demonstrate that the observed starch–I2 crystallization is governed by supramolecular E-Wc rather than individual ethanol or water molecules in the binary solution. By leveraging starch–I2 crystallization as a colorimetric bridge, we establish a direct correlation between E-Wc transitions and the iodine chromogenic effect. This approach enables the visual detection of transitions in colorless supramolecular assemblies, offering new insights into supramolecular science. Furthermore, as a simple, rapid, and visually interpretable detection method, this colorimetric probe holds promising applications in fields such as the food industry and supramolecular science.