Beyond uranium: dual-functional molybdenum polydopamine (Mo-PDA) nanomaterials for 99Mo/99mTc generator

Uranium-235 ( 235 U) has long been used for nuclear power generation, scientific research, and the production of medical radioisotopes. Amongst these, molybdenum-99 ( 99 Mo), produced via 235 U fission, is of particular importance as it decays to technetium-99 m ( 99m Tc), the most widely used radionuclide in diagnostic nuclear medicine. Despite its effectiveness, fission-based production generates large volumes of long-lived radioactive waste, raising long-term sustainability concerns. Alternative direct production routes using enriched 98 Mo or 100 Mo targets avoid fission-based waste but yield 99 Mo with very low specific activity, as chemical separation of 99 Mo from the bulk Mo target material is not feasible. Moreover, conventional alumina-based adsorbents cannot accommodate the high Mo loading required. To address these limitations, we report the development of a molybdenum-based material that simultaneously functions as both target and generator material. Molybdenum-polydopamine ( Mo-PDA ) nanomaterial was synthesized via the scalable oxidative polymerization route and evaluated as 99 Mo/ 99m Tc generator material. Mo-PDA exhibits a high surface area of 215 ± 10 m 2 /g, a thermal stability up to ~250 °C and excellent chemical stability with <0.0025% 98 Mo breakthrough after 24 h of incubation time in methylethylketone (MEK). Following neutron irradiation, Mo-PDA demonstrated consistent 99m Tc extraction efficiencies of ~25%, with negligible 99 Mo breakthrough in MEK over multiple irradiation cycles. Moreover, the Mo-PDA mostly retained its morphological integrity, with only minor irradiation-induced degradation observed after 30 h of irradiation exposure. However, irradiating at a ten times higher flux for 24 h resulted in the morphological degradation of Mo-PDA , limiting its potential for reuse as a target material over multiple irradiation-extraction cycles. In contrast, irradiation in a lead-shielded facility which significantly reduces γ-induced damage, preserving the Mo-PDA morphological integrity up to 140 h of irradiation time. After 168 h of irradiation time, only slight morphological degradation was observed, and the 99m Tc extraction efficiency from Mo-PDA decreased to ~15%. These results highlight Mo-PDA as a promising dual-functional material for 99 Mo/ 99m Tc generator application, with the potential for re-irradiation in a lead-shielded facility, offering a more sustainable and waste minimized alternative for production of 99m Tc for nuclear medicine.