Solution synthesis of nanocrystalline M-Zn (M = Pd, Au, Cu) intermetallic compounds via chemical conversion of metal nanoparticle precursors

Alloys and intermetallic compounds offer a wide range of desirable physical and chemical properties. However, accessing these compounds as nanocrystals is not always straightforward, and the continued development of appropriate synthetic pathways is required. Developing processes that are general toward many systems can be particularly challenging, especially when trying to incorporate highly electropositive metals or metals whose precursors are difficult to reduce into alloy or intermetallic compounds using solution chemistry strategies. Here we report a generalized strategy to access nanocrystalline M-Zn intermetallics (M = Au, Cu, Pd) via the chemical conversion of metal nanoparticles using zerovalent organometallic zinc precursors. Using commercially available reagents, transition-metal nanocrystals are made in hot organoamine solvents, which can be further reacted with diethylzinc or diphenylzinc to form intermetallic AuZn, Au3Zn, Cu5Zn8, and PdZn. The reaction pathway from the single-metal precursor to the intermetallic product is confirmed, and the overall particle morphology of the metal nanoparticle precursors is generally conserved in the intermetallic nanoparticle products throughout the conversion reaction. This method offers a general and robust route to zinc-based intermetallics with known catalytic, shape-memory, and corrosion-resistant properties.