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

Area of Science:

• Analytical Chemistry
• Spectroscopy
• Supramolecular Chemistry

Background:

• Distinguishing between heavy water (D2O) and regular water (H2O) is challenging due to their similar physical and chemical properties.
• Existing methods for detecting trace H2O in D2O are limited, hindering precise analysis in scientific research.
• Molecule-based spectral probes offer a potential avenue for differentiating these isotopes.

Purpose of the Study:

• To develop a novel method for distinguishing D2O from H2O.
• To quantify trace amounts of H2O within a D2O solvent.
• To explore the use of molecule-based spectral probes for this analytical task.

Main Methods:

• Utilized imine-based fluorescent probes designed to exhibit differential responses in D2O and H2O.
• Investigated hydrolysis reactions releasing fluorescent amines and aggregation-induced emission (AIE) of imines as dual fluorescence signals.
• Systematically varied imine structures to modulate hydrolysis and AIE, correlating hydrophobicity with solvent effects.

Main Results:

• Demonstrated that imine structure influences hydrolysis and AIE, creating distinct fluorescence signals in D2O versus H2O.
• Hydrophobicity of imines was identified as a key factor in modulating these differential fluorescence responses.
• Identified a specific probe (imine condensed from 2-naphthylamine and salicylaldehyde) as a promising candidate for detecting low H2O concentrations in D2O.

Conclusions:

• Developed a strategy using dual fluorescence signals from imine probes to differentiate D2O and H2O.
• Established that imine hydrophobicity is crucial for achieving selective detection in different water isotopes.
• The selected probe shows potential for accurate quantification of trace H2O in D2O solvents, particularly at low concentrations.