Di-Triphenylamine-based AIE active Schiff base for highly sensitive and selective fluorescence sensing of Cu2+ and Fe3+

Di-Triphenylamine based Schiff base (DTPA-SB) was obtained using facile synthetic steps, and the novel compound was thoroughly characterized using various spectroscopic techniques. The Schiff base showed aggregation-induced enhanced emission (AIEE) properties. In fact, a 7.6-fold increase in fluorescence intensity with a redshift of 24 nm was observed for a 10:90 DMF/water mixture of DTPA-SB, as compared to that in pure DMF. This significant AIEE behavior was further confirmed by the dynamic light scattering (DLS) experiment. Furthermore, this highly potential molecule was further applied for cation recognition using spectrofluorometric methods. In fact, DTPA-SB was found to recognize Cu2+ and Fe3+ ions selectively over a panel of ten heavy metals. The sensitivity of recognition was also significant with a limit of detection (LOD) of 0.4 and 0.2 ppb for Fe3+ and Cu2+, respectively. In order to investigate the mechanism further, the stoichiometry ratio of the DTPA-SB with Fe3+ and Cu2+ was obtained through Job’s plot. The ratio was found to be 1:2 (DTPA-SB:Metal) for both the metal ions. Furthermore, the binding constant of DTPA-SB for Fe3+ and Cu2+ were 5.5 × 1010 M−1 and 6.54 × 1010 M−1, respectively. On a parallel note, the aldehyde intermediate obtained during the synthesis of the Schiff base DTPA-SB exhibited solvatochromic properties. This nonlinear triphenylamine-based aldehyde (TPA-CHO) possess both donor and acceptor moieties, which can be utilized for the fabrication of color-tunable solution-processable OLEDs and sensors. Hence, the Schiff base has potential multifaceted applicability in the fields of heavy metal sensing, OLEDs and AIEE.