Ratiometric fluorescence “Turn On” probe for fast and selective detection of TNT in solution, solid and vapour

Fluorescent probe UREA-TP undergoes nearly 600% increase in emission intensity at 310 nm on addition of 1 equivalent of TNT, but the emission band centered at 440 nm remains unchanged. UREA-TP acts as a ratiometric fluorescence “turn-on” probe and can detect TNT between 10−9 to 10−5 M with limit of detection as low as 100 pM. Paper strips coated with UREA-TP on interaction with TNT become fluorescent purple under 365 nm light and can determine both qualitatively and quantitatively as low as 10 μl solution of 10−13 M TNT, which accounts for 2.27 × 10−16 g cm−2 TNT, significantly lower than the TNT concentration allowed in drinking water by EPA. The common nitroaromatic derivatives 2,4-DNT, 2,6-DNT, picric acid and 2,4-DNP, the pain killers, food supplements and inorganic anions show insignificant interference in the determination of TNT using UREA-TP. The aggregate size determination using dynamic light scattering analysis and morphological studies using TEM investigations reveals that UREA-TP in H2O-DMSO (98:2) remains in aggregate state with average size of 200 nm, which undergo further aggregation to larger size aggregates with increasing amounts of TNT.