Triphenylbenzene Sensor for Selective Detection of Picric Acid

A C3-symmetric triphenylbenzene based photoluminescent compound, 1,3,5-tris(4′-(N-methylamino)phenyl) benzene ([NHMe]3TAPB), has been synthesized by mono-N-methylation of 1,3,5-tris(4′-aminophenyl) benzene (TAPB) and structurally characterized. [NHMe]3TAPB acts as a selective fluorescent sensor for picric acid (PA) with a detection limit as low as 2.25 ppm at a signal to noise ratio of 3. Other related analytes (i.e. TNT, DNT and DNB) show very little effect on the fluorescence intensity of [NHMe]3TAPB. The selectivity is triggered by proton transfer from picric acid to the fluorophore and ground-state complex formation between the protonated fluorophore and picrate anion through hydrogen bonding interactions. The fluorescence lifetime measurements reveal static nature of fluorescence quenching.