More Benign Synthesis of Palladium Nanoparticles in Dimethyl Sulfoxide and Their Extraction into an Organic Phase

We present the successful synthesis and stabilization of 3.5 nm Pd nanoparticles (standard deviation of 0.49 nm) within dimethyl sulfoxide (DMSO) via fast, homogeneous reduction of a Pd salt using NaBH4 in the absence of traditional capping ligands. These Pd nanoparticles were found to be extremely stable and did not exhibit precipitation and/or agglomeration within the DMSO solvent even after more than 9 months. Moreover, these Pd nanoparticles were conveniently separated from the DMSO solvent medium via vacuum freeze drying by taking advantage of the high freezing point of DMSO. We have also successfully extracted the Pd nanoparticles from the DMSO phase into an organic phase (i.e., hexane), thereby providing a facile and efficient means for the generation of organic phase dispersible metal nanoparticles with complete recycle of the DMSO solvent.