A Novel 1,3,4-Oxadiazole-Based Fast Dual-Mode Sensor for the Detection of Iron and Lead Ions: Synthesis and...

In this study, a novel 1,3,4-oxadiazole aniline derivative (ODADA) was synthesized via a multistep synthetic method, and its structure was confirmed by FT-IR, ¹H NMR, ¹³C NMR, and ESI-MS results. The quantum chemical calculation was also conducted in detail, including geometry, electronic structure, charge distribution, and potential intramolecular charge transfer (ICT) behavior of ODADA. In addition, photoluminescence (PL) studies on solid-state samples were carried out, and PL emission maxima were observed between 511 and 543 nm. The photophysical properties of ODADA in the solution state have also been investigated by UV-vis absorption and fluorescence spectroscopy, and it emits deep blue fluorescence with the obtained absorption and emission maxima at 321-339 nm and 383-468 nm, respectively, and the fluorescence quantum yields (Φ) were found to vary between 0.01 and 0.42 in different solvents. Finally, sensor properties of ODADA were investigated for the selective determination of heavy metal ions. The molecule ODADA was observed to exhibit a significant colorimetric response to Pb²⁺ ions and a strong fluorometric response to Fe³⁺ ions. Spectroscopic analyses revealed a limit of detection (LOD) of 0.06 μM and a linear range of 0-150 μM for Pb²⁺ and an LOD of 0.10 μM and a linear range of 0-120 μM for Fe³⁺. Selectivity tests showed that the molecule exhibited superior specificity toward other metal ions. However, real sample tests using commercial hair dye showed that the ODADA sensor can also be used in practical applications. These findings demonstrate that the new 1,3,4-oxadiazole derivative offers significant potential for developing dual-mode (colorimetric and fluorometric) sensors for the reliable determination of heavy metal ions in environmental and biological samples.