Selective detection of picric acid by a fluorescent ionic liquid chemosensor

A fluorescent ionic liquid with a dansylamide chromophore was designed and synthesized, which exhibited strong green fluorescence both in the solution and in the condensed phase. As a fluorescent sensor, this ionic probe showed highly sensitive and selective detection of nitroaromatic explosives, especially for picric acid (PA). Theoretical calculations and NMR studies have demonstrated that a ground-state charge transfer through a protonation process and favorable electrostatic π-π interactions between ionic probe and PA may be responsible to the fluorescence quenching mechanism. Moreover, the resonance energy transfer (RET) studies explained the higher sensitivity and selectivity of this ionic probe towards PA than other nitro-containing explosives. A fluorescent test paper was also prepared for the on-site and accurate detection of PA, which provided a new clue of thoughts for instant and highly selective detection of nitroaromatic explosives.