  Non-equilibrium synthesis methods allow to alloy bulk-immiscible elements
into multinary nanoparticles, which broadens the design space for new
materials. Whereas sputtering onto solid substrates can combine immiscible
elements into thin film solid solutions, this is not clear for sputtering of
nanoparticles in ionic liquids. Thus, the suitability of sputtering in ionic
liquids for producing nanoparticles of immiscible elements is investigated by
co-sputtering the systems Au-Cu (miscible), Au-Ru and Cu-Ru (both immiscible),
and Au-Cu-Ru on the surface of the ionic liquid 1-butyl-3-methylimidazolium
bis-trifluoromethylsulfonyl)imide [Bmim][(Tf)2N]. The sputtered nanoparticles
were analyzed to obtain (i) knowledge concerning the general formation process
of nanoparticles when sputtering onto ionic liquid surfaces and (ii)
information, if alloy nanoparticles of immiscible elements can be synthesized
as well as (iii) evidence if the Hume-Rothery rules for solid solubility are
valid for sputtered nanoparticles. Accompanying atomistic simulations using
density-functional theory for clusters of different size and ordering confirm
that the miscibility of Au-Cu and the immiscibility of Au-Ru and Cu-Ru govern
the thermodynamic stability of the nanoparticles. Based on the matching
experimental and theoretical results for the NP/IL-systems concerning NP
stability, a formation model of multinary NPs in ILs was developed.
