Quinoline functionalized Tetramethoxyresorcin[4]arene supramolecular sensors for selective uranyl detection in...

Uranium contamination in aquatic environments poses a significant sensing challenge owing to its high toxicity and persistence. Effective detection of uranyl ions (UO₂²⁺) requires sensors that overcome matrix interferences and post-sampling instability, while enabling real-time, on-site monitoring. In this study, a series of tetramethylquinoline-substituted supramolecular sensors TMTQS (1a-1d) were designed and synthesized for the selective detection of UO₂²⁺ in aqueous environments. The TMTQS sensors were characterized by ¹H NMR, ¹³C NMR, and ESI-MS, and integrated into a dual-mode sensing platform combining fluorescence quenching with smartphone-assisted RGB colorimetry. Among the series, TMTQS 1a showed the highest binding affinity for UO₂²⁺ (Ka = 8.55 × 10⁷ M^-1), and achieved detection limits of 1.04 nM by spectrofluorimetric and 0.11 μM by smartphone-assisted RGB colorimetry. Job's plot confirmed a 1:1 binding stoichiometry between TMTQS sensors and UO₂²⁺ ions. FT-IR, NMR, and ESI-MS analyses supported the proposed binding mechanism. Thermodynamic analysis revealed spontaneous complexation at T = 298 K, (ΔH° = -33.89 kJ mol^-1, ΔS° = +41.17 J mol^-1K^-1, ΔG°₂₉₈ = -46.14 kJ mol^-1), driven by strong noncovalent interactions and desolvation, consistent with static fluorescence quenching and stabilization of the [TMTQS-UO₂²⁺] complex. The TMTQS sensors demonstrated excellent selectivity and practical utility, achieving recoveries greater than 95 % with RSDs below 2 % in spiked groundwater and seawater samples. These multifunctional TMTQS sensors enables highly selective, real-time detection of UO₂²⁺ in environmental waters, combining optical transduction with smartphone-based colorimetry to deliver a robust, pretreatment-free, and field-deployable solution for practical uranium monitoring.