Fluorescent and colorimetric sensors for selective detection of TNT and TNP explosives in aqueous medium through fluorescence emission enhancement mechanism

Due to rising threats of terrorism, pollution, timely and rapid detection of 2,4,6-trinitrophenol (TNP) and 2,4,6-trinitrotoluene (TNT) explosives has earned paramount significance. Herein, easily synthesized fluorenone sensor 3 was found selective towards the detection of TNP with a limit of detection (LOD) value of 0.5 nM. The fluorescence detection of TNP was achieved through the electrostatic interaction between sensor and TNP. Moreover, sensors 4 and 5 were rationally synthesized for selective nanoscale detection of TNT (LODs; 5.0 nM (4) and 7.0 nM (5)) through fluorescence emission enhancement response. Selective detection of TNT was accomplished through blockage of ICT and ESIPT in sensors. Sensing mechanisms were supported by 1H NMR titration, Job’s plots, computational methodologies, and DLS analysis. Interestingly, sensor 3 also showed selective colorimetric response towards TNP while sensors 4 and 5 displayed selective colorimetric detection of TNT explosive. Explosive responsive test kits were also prepared for on-site detection of TNP by sensor 3 and TNT by sensors 4 and 5. Moreover, sensors 3, 4, and 5 were successfully applied in the analysis of industrial effluents for the rapid detection of explosives.