An alternative phase-transfer method has been developed to prepare alkylamine-stabilized Pt nanoparticles. This method involves preparing a Pt hydrosol and then mixing the Pt hydrosol with a toluene solution of dodecylamine. This is followed by the addition of 1 M NaOH or 1 x PBS buffer to adjust the pH of the hydrosol to suitable values. Dodecylamine-stabilized Pt nanoparticles prepared this way had a predominantly cubic appearance, uniform size distribution, and self-assembled on transmission electron microscopy copper grids with an interparticle spacing of 2.2 nm. These results were then used to derive a protocol for preparing oligonucleotide-stabilized Pt nanoparticles in the aqueous environment. The oligonucleotide-stabilized Pt nanoparticles formed this way were either of spherical or irregular cubic shape depending on whether H-2-PtC1(6) or K(2)PtC1(4) was used as the starting metal salt.