Phase Transfer of Noble Metal Nanoparticles from Ionic Liquids to an Organic/Aqueous Medium

The synthesis of noble metal nanoparticles (NMNPs) using, or in the presence of, ionic liquids (ILs) represents a burgeoning direction in materials chemistry. Processing these nanomaterials synthesized in ILs would be drastically simplified if they could be routinely dispersed into a wide variety of polar/nonpolar solvents. We herein demonstrate the phase transfer of the as-prepared nanoparticles from ILs to an organic or aqueous medium. The protocol involves first mixing the noble metal sols in ILs and an ethanolic or a methanolic solution of transfer agent and then extracting the transfer-agent-stabilized NMNPs into toluene or aqueous phase. Electron micrographs reveal that the particles are fully dispersed after transfer, and the size/morphology of the NMNPs could be significantly tuned by the ILs. In particular, electrochemical measurements of the Pt nanoparticles upon methanol oxidation reaction demonstrate that the particles are dominated by low-index crystal planes.