Molybdenum silicide (nano)materials for 99Mo/99mTc generator applications

Abstract

The radionuclide technetium-99m (99𝑚Tc) is utilized in 80-85% of in-vivo nuclear medicine diagnostics due to its ideal physical and chemical properties, including a short half-life, gamma emission suitable for imaging, and versatile chemistry. Its production relies on molybdenum-99 (99Mo), traditionally generated through uranium fission. However, the transition to low-enriched uranium (LEU) targets and growing demand for 99𝑚Tc have driven the search for alternative production methods and materials. This study investigates the potential of molybdenum silicide (MoSi2) materials as targets for neutron-activated 99Mo production and as generators for 99𝑚Tc extraction. Three synthesis methods were explored to produce nanoscale molybdenum silicides. A sol-gel carbothermic reduction method failed to produce MoSi2, yielding elemental molybdenum, molybdenum dioxide, and molybdenum carbide due to oxygen contamination. The sol-gel preoxidation method successfully coated commercial MoSi2 with an amorphous silica layer, enhancing the material’s stability. The magnesiothermic reduction method successfully produced an oxide mixture intermediate (SiO2/MoO3) with nanosphere structures, initially containing 0.57 wt% molybdenum. The molybdenum content was later increased to 23.96 wt%. However, synthesis of the Si/MoSi2 nanocomposites from this intermediate was not completed due to time constraints. The chemical stability, extraction and retention behavior of commercial and silica-coated MoSi2 were evaluated in MilliQ and methyl ethyl ketone (MEK). The silica coating reduced molybdenum leaching and exhibited selective 99𝑚Tc extraction. Retention studies highlighted the significant role of solvent interactions in governing radionuclide adsorption. In MEK, the silica-coated material exhibited lower 99𝑚Tc retention, likely due to reduced adsorption sites caused by solvent interactions with silanol groups, while 99Mo retention could not be evaluated due to insufficient extraction data. The results demonstrate the potential of silica-coated MoSi2 in 99Mo/99𝑚Tc generator applications. However, further work is needed to optimize synthesis, increase surface area and evaluate long-term performance under irradiation. This could pave the way for sustainable and efficient isotope production systems.