Synthesis of rhenium oxide nanoparticles (RexOy) by gamma irradiation

Abstract Rhenium nanoparticles in the form of Re x O y were synthesized by gamma irradiation. A solution of sodium perrhenate in a mixture of water–isopropanol with a volume ratio of 2:1 was prepared. The solution was irradiated with a cobalt-60 gamma source with absorbed doses of 10, 20, 30 and 40 kGy. During gamma irradiation of water, strong oxidizing and reducing species are produced, thus isopropanol was primarily added in order to scavenge the oxidizing species. Radiolytic reduction of perrhenate ions leads to nucleation and growth of nanoparticles with average sizes between 10 and 55 nm. The size and size distribution of the resulting nanoparticles were investigated at three different concentrations of sodium perrhenate, 1, 3, and 5 mM, without the addition of any surfactant or stabilizer. Morphological and structural characteristics of the nanoparticles were performed with STEM, TEM, and UV–vis spectroscopy. Average particle size was found to increase in general with increased absorbed dose and initial concentration of sodium perrhenate. Nonetheless, for the 5 mM solution of sodium perrhenate, the particle size increased from 10 to 30 kGy and a decrease was observed at 40 kGy. The nanoparticles were found to be amorphous.