ESIPT-AIE based sequential fluorescence 'on-off' marker for endogenous detection of hypochlorite and cobalt (II)

Discrimination of a specific metal ion and ROS (Reactive Oxygen Species) among a library of ionic species in a water medium is one of the daunting tasks and it has been a hot-bed in the aspect of analytical chemistry. In the same objective, we have designed a tailor-fit molecule which serves as a sequential detector for ROS (-OCl) and a transition metal ion (Co2+). The novel receptor R has been derived from a simple condensation reaction between 2,5-thiophenedicarboxaldehyde and p-toluenesulfonyl hydrazide. The receptor is efficient for hypochlorite detection among all anions and other reactive oxygen species via 'turn-on' emission in 20% water (HEPES buffer, pH = 8) + DMSO medium without any interference through oxidative chemodosimetric mechanism. And the resultant emissive solution is extremely efficient for Co2+ among all cations via both change in colour and 'turn-off' emission. The obtained results are well supported by theoretical calculations. Limit of detection for hypochlorite and Co2+ are found to be 0.53 nM and 0.97 mu M, respectively. The receptor showed real-time working efficiency in a bleach solution and chocolate extract. The receptor is proven to be biocompatible and is applied for endogenous fluorescence cell imaging of hypochlorite and Co2+.