Aggregation induced emission enhancement from antipyrine-based schiff base and its selective sensing towards picric acid.

A heteroatom containing Schiff base, 4-[(2-Hydroxy-naphthalen-1-ylmethylene)-amino]-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazol-3-one (NDAP) has been synthesized using one step condensation method. Compound, NDAP is weakly emissive in solution state but a strong emission is observed in its aggregated state due to the restriction of intramolecular rotation (RIR) and large amplitude vibrational modes of NDAP. This phenomenon is known as aggregation induced emission enhancement (AIEE). Various morphologies of NDAP microstructures have been synthesized using reprecipitation method. SDS is also used as a morphology directing agent. Morphologies of the particles are characterized using optical and scanning electron microscopy (SEM). Photophysical properties of aggregated NDAP hydrosol are studied using UV–vis absorption, steady state and time resolved fluorescence spectroscopy. The ‘turn off’ luminescent property of aggregated NDAP hydrosol is used for the selective detection of trace amounts of picric acid in aqueous medium and the fluorescence quenching is explained due to ground state complexation between NDAP and picric acid with quenching constant (K q ), 1.91 × 10 5 M −1 . [ABSTRACT FROM AUTHOR]