Gamma-radiation-induced synthesis of metal and metal oxide nanoparticles involves reactions of dissolved precursor metal salts with products of water radiolysis. When exposed to ionizing radiation water decomposes to form chemically reactive radicals and molecular species. The products of water radiolysis range from highly oxidizing, e.g. hydroxyl radicals to highly reducing, e.g. hydrogen radicals and solvated electrons. The oxidants and reductants produced upon radiolysis react then with solutes and change their oxidation state. These chemical changes lead to the formation and subsequent precipitation of insoluble species, since the solubility and reactivity of metal ions depend on their oxidation states. Synthesis of nanomaterials can be done by using either reductive or oxidative routes. To reach the controlled redox conditions and avoid the unwanted reactions one can add other organic or inorganic compounds which act as scavengers of the radicals. The amount of material obtained by gamma- radiation-induced synthesis can be controlled by the yield of reductive/oxidative radiolysis products formed in solution. Radiation induced synthesis is a powerful tool to produce the materials of complex shape and compositions. It has the following advantages as compared to the other methods: The nanoparticles with very narrow size distribution and uniform shape can be synthesized; there are possibilities to synthesize the nanostructure in confined media, such as porous materials, nanotubes etc. The formation of radicals stops immediately when the solution is removed from the radioactive source. Therefore the amount of reacting radicals and thus the amount of obtained precipitate is controlled by the total radiation dose with a high accuracy. Moreover, the radiation induced method is cost-effective processing, since it implies direct energy transfer without intervening media. It has low energy consumptions, since the radiation source does not require external energy supply. It requires minimal use of potentially harmful chemicals (initiators, crosslinking agents, acids etc.). Thus, radiation-induced synthesis can be considered as a green method.
In the current work we demonstrate how gamma radiation induced synthesis can be implemented to produce metal (Ag, Cu, Ni) and metal oxide (Cu2O, Co3O4, CeO2) nanoparticles having narrow size distribution for different applications. The nanomaterials are produced both free standing and on solid supports. Metal nanoparticles are synthesized using the reductive route while metal oxide particles are produced using both oxidative and reductive routes [1, 2].
1. C. Dispenza, N. Grimaldi, M. A. Sabatino, I. L. Soroka and M. Jonsson, J. Nanoscale and Nanotechnol., 2015, 15, 3445-3467.
2. I. L. Soroka, N. V. Tarakina, A. Hermansson, L. Bigum, R. Widerberg, M. S. Andersson, R. Mathieu, A. R. Paulraj, Y. Kiros. Dalton Trans. 2017, 46, 9995-10002.