A general phase-transfer protocol for metal ions and its application in nanocrystal synthesis

Nanocrystals prepared in organic media can be easily self-assembled into close-packed hexagonal monolayers on solvent evaporation for various applications. However, they usually rely on the use of organometallic precursors that are soluble in organic solvents. Herein we report a general protocol to transfer metal ions from an aqueous solution to an organic medium, which involves mixing the aqueous solution of metal ions with an ethanolic solution of dodecylamine (DDA), and extracting the coordinating compounds formed between the metal ions and DDA into toluene. This approach could be applied towards transferring a wide variety of transition-metal ions with an efficiency of >95%, and enables the synthesis of a variety of metallic and semiconductor nanocrystals to be carried out in an organic medium using relatively inexpensive water-soluble metal salts as starting materials. This protocol could be easily extended to synthesize a variety of heterogeneous semiconductor/noble-metal hybrids and to nanocomposites with multiple functionalities.