Generalized route to metal nanoparticles with liquid behavior.

We report the generalized synthesis of metal nanoparticles with liquid-like behavior. We introduce a thiol-containing ionic liquid, N,N-dioctyl-N-(3-mercaptopropyl)-N-methylammonium bromide, which serves as a ligand for platinum, gold, palladium, and rhodium nanoparticles. A rapid reduction using THF-soluble metal salts in the presence of the thiol generates nanoparticles with tunable sizes and size distributions. The as-synthesized nanoparticles are a solid and decompose before melting. Upon exchange of the halide anion for an amphiphilic sulfonate anion, however, the nanoparticles exhibit liquid-like properties at room temperature. The liquids have high metal loadings; for example, the 2.7 nm platinum nanoparticle liquid is 36% platinum by mass.