A pyrene-thiophene based probe for aggregation induced emission enhancement (AIEE) and naked-eye detection of fluoride ions

Abstract

A pyrene based probe (E)-N’-(pyren-1-ylmethylene)thiophene-2-carbohydrazide (PTH), was synthesized and characterized by IR, NMR and HRMS spectroscopic tools. The probe exhibited aggregation induced emission enhancement (AIEE) in binary solvent mixture (ACN/water) on increasing water fraction and displayed bright yellow emission in solid state. Fluorescence spectroscopy, time resolved fluorescence and DLS analysis have been exploited to gain insight into the mechanism. These results indicated an enhancement in quantum yield and average lifetime with an increase in water content. In addition to intriguing AIEE property, PTH demonstrated excellent selectivity and sensitivity for F− over various other anions. A plausible mechanism for interaction of the probe with F− has been proposed on the basis of 1H NMR titration, absorption spectra and DFT study. The recognition process was found to be driven by the high electronegativity of F− leading hydrogen bonded adduct followed by deprotonation of PTH. Instant naked eye response along with commendable detection limit (2.02 × 10−7 M) and binding constant (6.18 × 104 M−1) increased the pertinency of the probe.