Combinatorial Synthesis of Binary Nanoparticles in Ionic Liquids by Cosputtering and Mixing of Elemental Nanoparticles.

Binary alloy nanoparticles were fabricated by two combinatorial methods: (I) cosputtering from elemental targets into the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [Bmim][(Tf)2N] and (II) by mixing elemental nanoparticles after sputtering them separately into [Bmim][(Tf)2N]. Both methods lead to the formation of Au-Cu nanoparticles (2.3 nm for cosputtered, 3.6 nm for mixed), however with different resulting compositions: cosputtered nanoparticles show a composition range of Au80-90Cu20-10; mixing of Au- and Cu-loaded ionic liquids leads to the formation of Au75Cu25 nanoparticles. Annealing the binary nanoparticles at 100 °C shows that the mixed nanoparticles grow to sizes of 4.1 nm, whereas the cosputtered nanoparticles grow only to 3 nm.