An improved procedure for preparing smaller and nearly monodispersed thiol-stabilized platinum nanoparticles

An alternative process was developed to prepare smaller and nearly monodispersed thiol-stabilized platinum nanoparticles. The procedure involves the reduction of a Pt(IV) precursor salt by a small (10%) stoichiometric excess of sodium borohydride in the presence of a toluene solution of 1-dodecanethiol. Complete reduction of the Pt precursor was confirmed by elemental analysis and UV-vis spectroscopy. The platinum nanoparticles prepared as such could be transferred directly to the toluene layer without the addition of concentrated hydrochloric acid that was previously reported as essential for the transfer to take place. TEM imaging shows a mean particle diameter of 2.6 nm and a nearly monodispersed particle size distribution (sigma = 0.44 nm). These results were used to formulate a protocol to prepare oligonucleotide-stabilized Pt nanoparticles with narrow particle size distribution and excellent stability in aqueous solutions.