Mechanistic Insight into Selective Sensing of Hazardous Hg2+ and Explosive Picric Acid by Using a Pyrene-Azine-Hydroxyquinoline Framework in Differential Media

Abstract

A pyrene-hydroxyquinoline tethered ingeniously designed and developed azine based Schiff base luminophoric system, 2-((Z)-((E)-(pyren-1-ylmethylene)hydrazono)methyl)quinolin-8-ol (PHQ) has been explored as a selective ‘TURN ON’ chromofluorogenic sensor for hazardous Hg2+ ions in ethanol/H2O (9 : 1,v/v) medium with detection limit of 0.22 μM and binding constant of 1.09 x 103 M−1. The detail scrutiny of mechanism of interaction between PHQ and Hg2+ is rationalized through various techniques like 1H NMR titration, FT-IR, mass spectral analysis, theoretical computations, Job's plot, dynamic light scattering (DLS), transmission electron microscopy (TEM), time resolved excited state decay dynamics and fluorescence reversibility studies, which concretely declare a synergistic effect of supramolecular aggregation induced enhanced emission and deactivation of photo-induced electron transfer (PET) processes. On the other hand, a ‘TURN OFF’ luminescence feature of highly fluorescent PHQ hydrosol is utilized for the selective screening of powerful explosive picric acid (PA) in aqueous medium and mechanism is deciphered by means of steady state, time-resolved emission as well as computational studies which altogether reflect a combined effect of PET and ground state complexation between probe and PA. The commendable detection limit of 55 nM and Stern-Volmer quenching constant of 1.48 x 104 M−1 with high quenching efficiency of 84% increases the pertinency of the nano-probe.