Synthetic fluorescent organic molecule for the detection of diethylcyanophosphonate via ON-OFF sensing mechanism: paper strips system for real-time application

Imidazo[1,2-a] pyridine-based two probes with different substituents containing oxime and hydroxyl functional groups were synthesised and evaluated for detection of tabun nerve agent simulant diethylcyanophosphonate (DCNP). The nucleophile hydroxyl group present on both the probes can be rapidly phosphorylated by DCNP through a nucleophilic substitution reaction. The probes were fluorescent and on reacting with DCNP underwent fluorescence OFF, which can be visualised under a UV lamp at 365 nm wavelength. The limit of detection for probes 1 and 2 was calculated as 0.66 μM and 0.54 μM, respectively. The mechanism of detection was studied using spectroscopic techniques revealed that the hydroxyl group is involved in the reaction with DCNP. The probes were found selective for the detection of DCNP in presence of other electrophilic interfering agents. Results were obtained in aqueous media and probes can be used directly for the rapid and sensitive detection of DCNP in water without any pretreatment.