Key-enabled molecular rotation modulates intramolecular hydrogen bonding toward a turn-on trace-level N2H4 sensor

Hydrazine (N 2 H 4 ) specifically hydrolyzes the ester group in the probe. This cleavage releases the highly fluorescent fluorophore from its initial quenched state, triggering a pronounced fluorescence “turn-on” response, enabling sensitive and selective detection of N 2 H 4 .