Nearly complete oxidation of Au0 in hydrophobized nanoparticles to Au3+ ions by N-bromosuccinimide

Au degrees atoms in hydrophobized gold nanoparticles were oxidized to Au3+ ions, nearly quantitatively, simply by treatment with N-bromosuccinimide and sonication. H-1 NMR results indicate that the octadecylamine molecules are detached from the Au degrees surface by NBS. The bromine molecules released by NBS are suggested to be the species responsible for the oxidation of Au degrees to Au3+, which is supported by the observation that addition of molecular bromine also leads to similar results. A gratifying feature is that the Au3+ ions could be subsequently reduced back to An nanoparticles.