Integration of Pyrene-Naphthalene units to develop AIE-active probes for selective detection of picric acid and antibacterial studies

The development of pyrene-based Schiff bases with aggregation-induced emission (AIE) characteristics has attracted significant consideration in recent times owing to probable applications in different fields. In this work, we report the synthesis of an AIE-active pyrene-naphthalene Schiff base (PSB) through a simple condensation reaction. The obtained product was systematically characterized using IR, NMR and mass spectroscopic techniques. In THF solution, the PSB molecule exhibited weak emission, whereas the gradual addition of water resulted in a marked enhancement of emission intensity, confirming its AIE behavior. UV, DLS, and SEM analysis further validated the AIE properties. Moreover, the rod-shaped aggregates have exhibited higher quantum yield and fluorescence lifetime, making them an appropriate material for sensor applications. Exploiting these properties, the PSB aggregates were used as a fluorescent material for the selective and sensitive detection of picric acid. The fluorescence quenching studies showed static quenching, with a calculated LOD of 80 nM. The mechanism of quenching was attributed to the inner filter effect, as confirmed by fluorescence lifetime analysis. For practical utility, we have developed a low-cost paper-based strip for sensing picric acid in the solid phase. Beyond sensing, the PSB molecule was evaluated for its antibacterial activity against bacteria such as Escherichia coliand S. aureus. The exact binding sites and interactions were analyzed through molecular docking analysis. Overall, PSB can be a prospective molecule as a multifunctional material for both chemical sensing and biological applications in solution and aggregated states.