Size control in the synthesis of 1-6 nm gold nanoparticles via solvent-controlled nucleation.

We report a facile synthetic route for size-controlled preparation of gold nanoparticles. Nearly monodisperse gold nanoparticles with core diameters of 1-6 nm were obtained by reducing AuP(Phenyl)(3)Cl with tert-butylamine borane in the presence of dodecanethiol in the solvent mixture of benzene and CHCl3. Mechanism studies have shown that the size control is achieved by the solvent-controlled nucleation in which the nuclei concentration increases with increasing the fraction of CHCl3, leading to smaller particles. It was also found that, following the solvent-controlled nucleation, particle growth occurs via ligand replacement of PPh3 on the nuclei by Au(I)thiolate generated by the digestive etching of small particles. This synthetic strategy was successfully demonstrated with other alkanethiols of different chain length with which size-controlled, monodisperse gold nanoparticles were prepared in remarkable yield without requiring any postsynthesis treatments.