Hydrazone-derived PET/CHEF fluorescent probes for sensitive detection of cesium and strontium in real samples

In this study, two hydrazone-based probes, NSP ((E)-5-(diethylamino)-2-((2-(2,4-dinitrophenyl)hydrazineylidene)methyl)phenol) and NFH ((E)-N'-(4-(diethylamino)-2-hydroxybenzylidene)furan-2-carbohydrazide), were developed and synthesized for the specific detection of Cs⁺ and Sr²⁺ ions, respectively. Both probes were very sensitive, with low detection limits of 2.4 nM for Cs⁺ and 22 nM for Sr²⁺, along with high selectivity over other metal ions. The binding constant is 4.8 × 10⁷ M^-1 for NSP-Cs⁺ and 6.4 × 10⁵ M^-1 for NFH-Sr²⁺. Job's plot analysis confirmed a 1 : 1 binding stoichiometry between the probes and their corresponding metal ions. The NSP- and NFH-functionalized cotton swabs exhibit excellent stability, highlighting their potential for portable and on-site detection. Complementarily, their efficacy was demonstrated in actual samples, including water, soil, and vegetable matrices, achieving excellent recovery results.