Efficient elimination and naked-eye detection of trace radioactive iodide by silver-decorated oxygen vacancy-rich TiO_2-x derived from MIL-125

The development of efficient radioactive iodine management technologies is crucial for ensuring the sustainable utilization of nuclear energy. Herein, silver nanoparticle-modified oxygen-rich vacancy TiO_2-x (Ag₂O-Ag@TiO_2-x, AT) nanocomposites were successfully synthesized via a controlled pyrolysis-reduction strategy using a Ti-based MOF (MIL-125) as the precursor. The synergistic effect of oxygen vacancies and Ag/TiO_2-x Schottky junctions endowed the material with exceptional iodide adsorption performance through a photocatalytic oxidation-adsorption mechanism, achieving a maximum adsorption capacity of 143.9 mg g⁻¹. Notably, the AT nanocomposites maintained high adsorption efficiency (removal rate > 95%) even for trace-level iodide ions (down to 300 μg L⁻¹). Furthermore, the material exhibited superior iodoperoxidase-like activity, enabling highly sensitive colorimetric detection of iodide with a detection limit of 1.33 μM. This sensing mechanism relies on H₂O₂-mediated oxidation of I⁻ to reactive iodine species (IO₃⁻), which subsequently convert 3,3′,5,5′-tetramethylbenzidine (TMB) into oxidized TMB (ox-TMB). Combined experimental and theoretical analyses elucidated the underlying mechanisms governing iodide adsorption and sensing. This work not only provided fundamental insights into iodine-material interactions but also offered a practical solution for environmental monitoring and nuclear waste management, effectively addressing critical challenges in radioactive iodine remediation.