Post-effects of radioactive decay in magnetite nano-crystals labelled with Auger- and internal conversion electron-emitters, alpha- and beta decay radionuclides

By applying the standard technique of co-precipitation of ferric- and ferrous salts with ammonium hydroxide in an inert atmosphere, the magnetite nano-crystallites have been prepared labelled with Auger- and internal conversion electrons, beta- and alpha-emitters (57Co, 60Co and 241Am radionuclides). It has been confirmed by the methods of both X-ray phase analysis and Absorption Mössbauer Spectroscopy that for both cases (the “pure” crystallite and the ones doped with radionuclides), it is nanoparticles of a spherical shape that were synthesized with a magnetite structure and crystallites with a diameter of 12–18 nm; there were no admixtures of other iron compounds detected. It has been shown that the governing stabilization factor for the daughter iron atoms that were produced in 57Co(II) as a result of electron capture (EC) is the size of the atom whose position is originally occupied by the parent atom: in the emission spectra there are only Fe2+-species “present”. A comparative analysis has been conducted of radiation-induced damage patterns in nano-crystallites in the dependence of nuclear- and physical characteristics of the radioactive tracer and total fluence. It has been established that under irradiation there is a comminution of crystallites taking place, the effective magnetic fields on the iron atoms in the labelled nano-crystallites remaining unchanged irrespective of the “dose load”. Resulting from the decay of 241Am, the daughter nucleus receives the energy of 92.3 keV, the range of 237Np nuclei (while the account is taken of the entire cascade of possible collisions) amounting to almost 40 nm, which is twice the size of “nano-containers” (the escape of 237Np from the volume of crystallites is experimentally confirmed by the method of 2πα-counting). •Post-effects of decay of 57Co, 60Co and 241Am in Fe3O4 nano-crystals were studied.•The X-ray analysis, alpha-, gamma- and Mössbauer spectroscopy were used.•Irradiation with α-particles leads to crushing (up to 25–30%) of nano-crystallites.•The range of the 237Np recoil nucleus is twice the size of the nano-crystallites.•Medical purposes (α-therapy) require “containers” with a particle size of 80–120 nm.