Fast and easy detection of hypochlorite by a smartphone-based fluorescent turn-on probe: Applications to water samples, zebrafish and plant imaging

We have developed a fluorescent probe DBT-Cl ((E)-2-(2-(4-(diphenylamino)benzylidene) hydrazinyl)-N,N,N-trimethyl-2-oxoethan-1-aminium chloride) for ClO⁻ with an aggregation-induced emission (AIE) strategy depending on solvent polarity. DBT-Cl possessed a prominent solvatochromic emission property with intramolecular charge transfer (ICT) from the TPA (triphenylamine) to the amide group, which was studied by spectroscopic analysis and DFT calculations. These unique AIE properties of DBT-Cl led to the recognition of ClO⁻ with high fluorescent selectivity. DBT-Cl quickly detected ClO⁻ in less than 1 sec with a fluorescent color change from green to cyan. DBT-Cl had a low detection limit of 9.67 μM to ClO⁻. Detection mechanism of DBT-Cl toward ClO⁻ was illustrated to be oxidative cleavage of DBT-Cl by ¹H NMR titrations, ESI-mass, and DFT calculations. We established the viability for dependable detection of ClO⁻ in actual water samples, as well as zebrafish and plant imaging. In particular, DBT-Cl was capable of easily monitoring ClO⁻ through a smartphone application. Therefore, DBT-Cl assured a promising approach for a fast-responsive and multi-applicable ClO⁻ probe in environmental and living organism systems.