A novel method for synthesis of 56Co-radiolabelled silica nanoparticles

A method for synthesis of radiolabelled amorphous silica nanoparticles is presented. The method is based on the well-known Stober process with the exception that 56Co radiotracer is introduced into one of the precursor materials prior to the initiation of the nanoparticle synthesis. The 56Co was prepared by proton irradiation of an iron foil, followed by dissolution in hydrochloric acid and 56Co/Fe radiochemical separation. In order to determine the residual Fe in the 56Co radiotracer solution, ICP-MS measurements were performed. Nanoparticles in the size range 20–100 nm were synthesised and characterised by gamma spectrometry, ICP-MS, XRD, DLS, and Zeta potential measurement. It was shown that the size and Zeta potential of the nanoparticles was roughly the same following synthesis with or without added 56Co, and in both cases, the structure was that of amorphous silica. It was found that 99.5 % of the 56Co was bound into the nanoparticles during synthesis, and centrifugation experiments confirmed that the radiolabels were stably incorporated into the silica matrix.