Quinoline-quinoline schiff-base as an effective chromogenic, fluorogenic, and smartphone assisted RGB detection of Pb2+ ion in near aqueous medium.

A novel multimode colorimetric and fluorescent chemosensor was developed using an 8-hydroxy quinoline carbaldehyde Schiff base with a quinoline hydrazide probe (E)-2-((2-(quinolin-2-yl)hydrazineylidene)methyl)quinolin-8-ol (L). NMR (1H &13C), FTIR, and HR-mass spectral characterization techniques confirmed the probe L structural conformation. As Probe L contacts Pb2+ ions, a color change and turn-off emission can be visually detected in EtOH:H 2 O (1:1, v/v, pH = 7.21) medium. The probe displays a good emission at 440 nm due to the combined ESIPT and ICT process. The Pb2+ ion interacts with the probe and selectively quenches fluorescence by inhibiting ESIPT and >C N- isomerization. As per Job's plot, L-Pb 2+ complex formation occurred in a 1:1 stoichiometric ratio, with association constant (K a) and quenching constant (K sv) estimated at 1.52 × 105 M−1 and 4.12 × 105 M, respectively. The detection limits of Pb2+ by spectrophotometric and spectrofluorometric were 1.99 μM (41 ppb) and 23.4 nM (485 ppt), respectively. Additionally, the test paper kit and RGB tool were used to monitor the color changes of L with Pb2+ and the LOD was found to be 5.99 μM (125 ppb). Its recognition mechanism has been verified by 1H NMR, ESI-mass, and theoretical studies. [Display omitted] • Quinoline-Quinoline based probe (L) was Synthesized and Characterized by NMR, IR, and Mass. • Probe L shows visually detectable color change with Pb2+ via turn-off emission. • The LOD of Pb2+ by spectrophotometric and spectrofluorometric were 41 ppb and 485 ppt, respectively. • Used smartphone RGB tool and test paper kit for real-time Pb2+ ion detection. [ABSTRACT FROM AUTHOR]