Reversible growth of UO2 nanoparticles in aqueous solutions through 7 MeV electron beam irradiation

Uranium dioxide (UO2) nanoparticles of rod-shaped structures with diameter 80 nm and length 500 nm, have been grown in aqueous solutions of uranyl nitrate with electron beam irradiation using a 7 MeV linear electron accelerator. These nanoparticles were found to be stable under de-aerated condition; however they decomposed upon exposure to air or oxygen. The bimolecular rate constant for decomposition of these nanoparticles has been estimated to be 4.3 × 10−1 M−1 s−1, in the aerated and oxygen saturated solutions, assuming these to be of pseudo-first order processes. The nitrogen-purged decomposed solution again produced the black coloured UO2 sol upon such irradiation and these reversible phenomena could be repeated for several cycles. There was also decomposition of the UO2 nanoparticles along with evolution of hydrogen upon addition of acid in the de-aerated condition.

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► Rod-shaped UO2 nanoparticles were synthesised in water via electron beam irradiation.
► The appearance of black UO2 sol was observed a few minutes after the irradiation.
► The as-grown UO2 nanoparticles were decomposed upon exposure to air or oxygen.
► Rod-shaped UO2 nanoparticles were again formed from the decomposed solution upon irradiation.
► H2 was generated along with decomposition of the as-grown UO2 nanoparticles upon addition of acid.