Low-temperature solution synthesis of the non-equilibrium ordered intermetallic compounds Au₃Fe, Au₃Co, and Au₃Ni as nanocrystals

Alloys and intermetallic compounds of Au with the 3d transition metals Fe, Co, and Ni are nonequilibrium phases that have many useful potential applications as catalytic, magnetic, optic, and multifunctional magneto-optic materials. However, the atomically ordered Au-M (M = Fe, Co, Ni) intermetallics are particularly elusive from a synthetic standpoint. Here we report the low-temperature solution synthesis of the L1₂ (Cu₃Au-type) intermetallic compounds Au₃Fe, Au₃Co, and Au₃Ni using n-butyllithium as a reducing agent. Reaction pathway studies for the Au₃Co system indicate that Au nucleates first, followed by Co incorporation to form the intermetallic. The nonequilibrium intermetallic nanocrystals have been characterized by powder XRD, TEM, EDS, selected area electron diffraction, and nanobeam electron diffraction, which collectively confirm the compositions and superlattice structures.