Radiochemical synthesis of super(105g)Ag-labelled silver nanoparticles

A method for synthesis of radiolabelled silver nanoparticles is reported. The method is based on proton activation of silver metal powder, enriched in super(107)Ag, with a 30.7 MeV proton beam. At this proton energy super(105g)Ag is efficiently created, mainly via the super(107)Ag(p,3n) super(105)Cd arrow right super(105g)Ag reaction. super(105g)Ag has a half-life of 41.29 days and emits easily detectable gamma radiation on decay to super(105)Pd. This makes it very useful as a tracing radionuclide for experiments over several weeks or months. Following activation and a period to allow short-lived radionuclides to decay, the powder was dissolved in concentrated nitric acid in order to form silver nitrate (AgNO sub(3)), which was used to synthesise radiolabelled silver nanoparticles via the process of sodium borohydride reduction. For comparison, non-radioactive silver nanoparticles were synthesised using commercially supplied AgNO sub(3) in order to check if the use of irradiated Ag powder as a starting material would alter in any way the final nanoparticle characteristics. Both nanoparticle types were characterised using dynamic light scattering, zeta-potential and X-ray diffraction measurements, while additionally the non-radioactive samples were analysed by transmission electron microscopy and UV-Vis spectrometry. A hydrodynamic diameter of about 16 nm was determined for both radiolabelled and non-radioactive nanoparticles, while the electron microscopy on the non-radioactive samples indicated that the physical size of the metal NPs was (7.3 plus or minus 1.4) nm.