A New Acridine-Based Fluorescent Sensor for the Detection of CN−

A novel acridine-based fluorescent sensor (Sensor ANT) for the highly selective and sensitive detection of cyanide ions (CN−) was rationally designed and synthesized via the conjugation reaction of acridine-9-amine with 3-nitrophenyl isothiocyanate. The sensing mechanism is triggered by the specific interaction between exogenous CN− and the hydrogen-bonding moieties within the sensor’s molecular framework, which induces a distinct fluorescence quenching response. Systematic titration experiments confirmed that Sensor ANT exhibits rapid response kinetics, excellent selectivity, and reliable qualitative/quantitative detection capabilities toward CN−. Complementary biocompatibility assays, including in vitro cellular imaging and in vivo zebrafish experiments, further verified the promising application potential of this sensor in practical and biological detection scenarios. The detection limit (DL) of Sensor ANT for CN− was calculated to be 2.89 × 10−7 M, with a 1:1 binding stoichiometry and a binding constant of 1.95 × 104 M−1. These findings demonstrate that Sensor ANT represents a robust candidate for CN− detection in environmental and biological systems.