An Acylhydrazone Fluorescent Sensor: Bifunctional Detection of Thorium (IV) and Vanadyl Ions over Uranyl and Lanthanide Ions

Thorium is a notable candidate for resolving uranium shortage caused by the global application of nuclear power generation. Uranium extraction from seawater is another attempt to handle its source deficiency, however, vanadium is one of the main competitive elements in that process. Exploration of probes which can discriminatively detect thorium and vanadium from uranium has primary significance for their further separation and for environmental protection. Herein, N′-(2,4-dihydroxybenzylidene)-4-hydroxylphenylhydrazide,AOH, is used as sensor for Th4+and vanadyl (VO2+) determination.AOHdemonstrates a specific “turn-on” fluorescence selectivity towards Th4+over f-block and other foreign metal ions, with a detection limit (LOD) of 7.19 nM in acidic solution and a binding constant of 9.97 × 109M−2. Meanwhile, it shows a “turn-off” fluorescence response towards VO2+over other metal ions at the coexistence of Th4+, with a LOD of 0.386 μM in the same media and a binding constant of 4.54 × 104M−1. The recognition mechanism, based on HRMS,1H NMR, and FT-IR results, demonstrates that VO2+causes the fluorescence quenching by replacing Th4+to coordinate withAOH. In real water detection tests, Th4+and VO2+exhibited satisfying recoveries. These findings expand the application of sensors in nuclide pollution control.