Dual‐Responsive Excited‐State Intramolecular Double‐Proton Transfer‐Based Optical Probe for Hypochlorite and Picric Acid Detection With Applications in 3D‐Printed Indicators, Biosensing, and Theranostics

A dual‐mode fluorescent probe incorporating aggregation‐induced emission (AIE) activity, named 2‐((E)‐1‐(((E)‐4‐(diethylamino)‐2‐hydroxybenzylidene)hydrazineylidene)ethyl)naphthalen‐1‐ol ( DHN ), was formulated and synthesized for the selective detection of explosive picric acid (PA) and hypochlorite (OCl − ) via suppression of the excited‐state intramolecular double‐proton transfer (ESIDPT) mechanism. A significant fluorescence quenching of DHN at 535 nm was observed upon interaction with both PA and OCl − with the detection limits at 0.012 μM and 2.34 μM as well as high quenching efficiencies ( K sv ) of 3.811 × 10 4 M −1 and 1.164 × 10 4 M −1 , respectively. To elucidate the sensing behavior, various spectroscopic techniques were employed. Interestingly, DHN exhibited AIE behavior in high water content, showing a red‐shifted emission accompanied by a visible fluorescence change from whitish green to yellow. As a novel application, DHN was incorporated into a 3D‐printed polymer system, demonstrating its practical utility in detecting PA and OCl − . Further, for biological relevance, the interaction of DHN with OCl − was explored for its cytotoxicity against MCF‐7 breast cancer cells and its imaging capability in physiological media. Therefore, we believe that the present work provides a promising direction for the future development of optical‐based detection of hypochlorite and picric acid in liquid as well as solid phases.