“ON-OFF” novel fluorescent chemosensors based on nanoaggregates of triaryl imidazoles for superselective detection of nitro-explosive trinitrophenol in multiple solvent systems

Abstract Novel fluorescent chemosensors with a triaryl-substituted imidazole (TAI) moiety were synthesized, which exhibited strong fluorescence. These fluorescent chemosensors allowed highly sensitive and selective detection of nitroaromatic explosive, trinitrophenol (TNP). The TAI were successfully transformed to fluorescent organic nanoparticles (FONPs) in aqueous medium using re-precipitation method thus enabling fluorescent based detection of TNP in aqueous medium also. We hereby present simple and selective chemosensors that are highly sensitive towards TNP and not-sensitive towards interfering analytes. In light of Stern-Volmer plots, Benesi–Hildebrand plots and 1 H NMR titrations; it was confirmed that there exist competent interactions between the chemosensors and TNP. A detailed study revealed that synergistic effect of photo-induced electron transfer, electrostatic interaction and inner filter effect resulted in fluorescence quenching of chemosensors on the addition of TNP. The compounds are practically applicable for sensing TNP in real environmental samples as they gave good sensing response towards TNP in pH range of 5–9. Fluorescent test strips were fabricated which allowed effective on-site visual detection of explosive compound (TNP). To the best of our knowledge, this chemosensor represents the first example of TNP detection in aqueous medium using FONPs of TAI.