Trace level detection of Pb²⁺ ion using organic ligand as fluorescent-on probes in aqueous media

In this study, an optical sensor, JA/(2,6-di((E)-benzylidene)cyclohexan-1-one), was synthesized and characterized using ¹H NMR and FT-IR spectroscopy. The sensor exhibited high efficiency and selectivity in detecting Pb²⁺ ions, even in the presence of potential interfering ions such as Mn²⁺, Cu²⁺, Co²⁺, Cr³⁺, Ni²⁺, Ce³⁺, Hg²⁺, and Cd²⁺ in aqueous solutions. The interaction of JA with Pb²⁺ resulted in a significant enhancement of fluorescence intensity, suggesting the formation of a stable complex. A 2:1 binding ratio between JA and Pb²⁺ was confirmed through fluorometric analysis, absorption spectra, and theoretical calculations (DFT). The association constant for the complex was calculated to be 3 × 10⁶ M^-2. The sensor demonstrated high sensitivity towards Pb²⁺ with a detection limit of 5 × 10^-7 M. Additionally, JA was successfully reused by applying EDTA to release Pb²⁺ from the sensor. Real sample analysis under optimized conditions of pH, time, and concentration of JA and Pb²⁺ further validated the practical applicability of the sensor.