High-Sensitivity Measurement of Crystallization Induction Period Based on Fluorescence Method

In order to identify the crystallization induction period precisely, this study developed a fluorescence method based on aggregation-induced emission (AIE) characteristics. Accurate identification of the early stage of nucleation was made possible by tracking molecular aggregation through monitoring of the fluorescence intensity using N-phenylanthranilic acid (NPAA) as the model compound. The results showed that the fluorescence method had a significantly greater sensitivity and detected nucleation earlier than the traditional visual inspection method. Furthermore, a combination of experimental analysis and molecular dynamics simulations was employed to investigate the regulatory effects of surfactants on the nucleation process. Tetradonium bromide (TTAB) promoted nucleation by reducing the nucleation barrier through electrostatic attraction and hydrophobic interactions, thereby accelerating crystal formation. On the other hand, by enhancing solvation effects and electrostatic repulsion, sodium dodecyl sulfate (SDS) prevented molecular aggregation and resulted in a longer induction period. This study showed the important regulating role of surfactants in the crystallization process in addition to validating the effectiveness of the fluorescence method.