Nanoarchitecture governs uranyl capture: From DTPA-derived carbon dots to magnetic nanohybrids and layered double hydroxides

Efficient treatment of uranium contaminated water requires sorbents that combine strong uranyl affinity, high site accessibility, operational selectivity and easy recovery. Here, we establish an architecture-dependent framework for uranyl capture by deploying the same chelation concept across three complementary platforms: DTPA derived Nitrogen-doped carbon dots (NCDs) as molecular recognition probes, covalently coupled magnetic nanohybrids (AMNP-NCD) as recoverable interfacial adsorbents, and DTPA-intercalated magnetic layered double hydroxides (DTPA-MNP/LDH) as interlayer-confined sorbents. NCDs exhibited pronounced optical response toward UO22+ through fluorescence quenching and UV-visible spectral changes, while nano-isothermal titration calorimetry demonstrated two spontaneous binding events with high affinity constants of 4.8 × 105 and 4.3 × 107 M−1, confirming strong uranyl coordination at DTPA-derived O/N-rich sites. Translation of this chemistry into solid-state architectures generated distinct uptake regimes. The covalent magnetic nanohybrid AMNP-NCD by EDC/NHS chemistry reached a maximum adsorption capacity of 443 mg g−1 and 97.2% uranyl removal at pH 6, while maintaining preferential uptake in the presence of competing cations and enabling rapid magnetic separation. In parallel, DTPA intercalation into MNP/LDH increased uranium uptake from 127 to 223 mg g−1. Mechanistic characterization by FTIR before and after U(VI) loading revealed coordination-driven interactions between uranyl ions and N/O-rich functional groups, whereas VSM analysis confirmed the preserved magnetic stability of the engineered nanocomposite. Comparative analysis shows that AMNP-NCD is governed mainly by accessible surface complexation, whereas DTPA-MNP/LDH combines interlayer confinement, complexation and ion-exchange contributions. These results demonstrate that ligand chemistry defines intrinsic affinity, whereas nanoarchitecture controls the usable capacity, transport pathway and processability of uranyl capture. The work provides actionable design rules for advanced materials in radiochemical water treatment and nuclear wastewater remediation.