A new one-phase synthesis of thiol-functionalized platinum nanoparticles is presented. Using tetrahydrofuran as the solvent and lithium triethylborohydride ("superhydride") as the reducing agent, platinum nanoparticles functionalized by octadecanethiol were prepared. Fourier transform infrared spectroscopy (FTIR), tunneling electron microscopy (TEM), and powder X-ray diffraction were used to analyze the nanoparticles. The results show that the nanoparticles are single crystals with fee structure, that their average size is similar to 3 nm, and that the octadecyl chains are close packed in a solid-like assembly.