Modulating Dual Fluorescence Emissions in Imine-Based Probes to Distinguish D2O and H2O

How to distinguish D2O and H2O and determine the trace H2O content in D2O solvent, by using molecule-based spectral probes, is an intriguing topic in analytical chemistry, yet considerably few examples remain up to now, likely due to the very similar physical/ chemical properties between D2O and H2O. In this work, we found that both the hydrolysis reactions to release fluorescent amines and aggregation-induced emission (AIE) of imines, functioning as dual fluorescence signals to distinguish D2O and H2O, could be modulated by changing the imine structures. The hydrophobicity of imines showed an important contribution to the ability of modulating the hydrolysis reactions and AIE, demonstrating a significant difference on fluorescence signals in D2O and H2O solvents. Among all tested imines, probe 3, condensed from 2-naphthylamine and salicylaldehyde, was found to have the potential ability to act as an ideal candidate for probing the H2O content in D2O solvent, particularly in a low H2O content range, using the ratiomeric emission signals.