pH‐Responsive Fluorescence Change Based on Dynamic Exchange between Emitting Aggregates and Quenching Monomers in Donor–Acceptor Dyes Bearing Carboxylic Acid Groups

Abstract

pH imaging and measurement in biological systems is important because changes in pH are closely related with physiological and pathological processes. In this paper, a pH‐responsive fluorescence change based on the dynamic exchange between emitting aggregate state and quenching monomer state is reported. At low pH, the aggregate bearing a neutral carboxylic acid group in its protonated form continues to emit red light. In contrast, at high pH, the aggregate dissociates to the fluorescence‐quenching monomer owing to electrostatic repulsion among the anionic carboxylate moieties generated from the deprotonation process, resulting in a pH‐responsive change.

Lignin-Derived Carbon Dot/Cellulose Nanofiber Films for Real-Time Food Freshness Monitoring

“…Since r-CDs can be seen as a conjugate structural core with some different functional groups on the surface, these conjugated structures can form large aggregates in an acidic environment, resulting in the shift of absorption peaks . At higher pH values, the aggregates dissociate into monomers due to the electrostatic repulsion between carboxyl groups generated in the process of deprotonation, resulting in the pH response change between the quenched aggregates and the emitting monomers …”

“…43 At higher pH values, the aggregates dissociate into monomers due to the electrostatic repulsion between carboxyl groups generated in the process of deprotonation, resulting in the pH response change between the quenched aggregates and the emitting monomers. 44 Meanwhile, the effect of different metal ions on the luminescence performance of the probe was investigated (Figure S2c), and the fluorescence intensity of the probe decreased to some extent in the presence of Cu 2+ , Fe 3+ , and Mg 2+ .…”