β-MoO_3 nanowhiskers in the development of ~(99)Mo/~(99m)Tc medical radioisotope preparation using a hot atom mechanism

摘要

In the production of Tc-~(99)M (radiopharmaceuticals), the neutron activation (n,γ) method using MoO_3 pellet is consideredto have more benefits than the nuclear fission products (n,f) method [1]. However, the low specific activity of ~(99)Mo hasbarred large scale manufacture. Currently, as the ~(99)Mo extraction process in the (n,γ) method, high-density pellets ofMoO_3 after the irradiating are considered diluted in NaOH solution [2]. Therefore, it consumes time and has difficultiesin separating and recovering compounds. Instead of this process, a hydrous MoO_3 target has been proposed to overcomethese problems and promise to increase the effectiveness of the (n,γ) method using a hot atom mechanism of irradiatedsamples. This target requires a porous structure with a suitable filtering property. Whisker is a suitable candidate withexcellent filtered property. Among MoO_3 phases, β-MoO_3 is the best catalyst caused by its crystal structure with a largerspace among valent binding of Mo and O than the other phases [3]. Therefore, it is a good condition for water can gothrough and wash the hot atom from the irradiated target. β-MoO_3 nanowhiskers were only synthesized by pulsed wiredischarge, in which the purity was low [4]. In this research, a β-MoO_3 nanowhisker with a width of 10 nm was synthesizedby thermal evaporation method with the oxygen gas flow at 750, 800, 850, 900, and 1000 ºC. The samples werecharacterized and confirmed by XRD in Fig. 1 and lattice image by FE-TEM in Fig. 2. From this work, the high contentand purity of β-MoO_3 nanowhiskers were synthesized by the thermal evaporation method. This sample is a promisingmaterial for the irradiation target in the (n, γ) method.