Metal nanoparticles (MNPs) with a small diameter and narrow size distribution can be prepared by H2 reduction of metal compounds or decomposition of organometallic species dissolved in ionic liquids (ILs). MNPs dispersed in ILs are catalysts for reactions under multiphase conditions. These soluble MNPs possess a pronounced surfacelike rather than single‐site like catalytic properties. In other cases the MNPs are not stable and tend to aggregate or serve as reservoirs of mononuclear catalytically active species.

The sputtering of gold foil onto 1-n-butyl-3-methylimidazolium tetrafluoroborate, hexafluorophosphate, bis(trifluoromethylsulfonyl)amide, or tris(fluoro)tris(perfluoroethane)phosphate ionic liquids (ILs) generates stable and well-dispersed gold nanoparticles (NPs) of 3-5 nm under conditions of 40 mA, 335 V, and 2 Pa Ar work pressure. The size and size distribution of these Au nanoparticles depends on various experimental parameters, particularly the surface composition of the IL and less so the surface tension and viscosity. Under the experimental conditions used here, both nucleation and NP growth seem to occur on the IL surface and the NP size changes with the changes in the IL surface composition, especially with the increase of the fluorinated content. Moreover, the NP size is independent of sputtering time but does depend on the discharge current. When higher discharge currents are used, more gold atoms hit the ionic liquid surface per unit time, changing the kinetics of particle growth on the surface of the IL.

The diameter and size-distribution of Ni nanoparticles prepared by the decomposition of [bis(1,5-cyclooctadiene)nickel(0)] organometallic precursor dissolved in 1-alkyl-3-methylimidazolium N-bis(trifluoromethanesulfonyl) amide ionic liquids depend on the length of the alkyl side-chain of the imidazolium ring. The increase of the organization range order of the ionic liquid that increases with that of the alkyl side-chain (from n-butyl to n-hexadecyl) induces the formation of nanoparticles with a smaller diameter and size-distribution. The cubic fcc Ni nanoparticles with 4.9 +/- 0.9 to 5.9 +/- 1.4 nm in mean diameter and monomodal size-distribution thus prepared are probably composed of a small cap layer of NiO around a core of Ni metal. The contribution of the oxide layer also depends on the medium i.e. the metal oxide ratio increases in salts containing four to eight carbons on their side-chains and then decreases as the number of carbons increases. The Ni nanoparticles dispersed in the ionic liquids are active catalysts for the hydrogenation of olefins under relatively mild reaction conditions.

No abstract

The sputtering of Au targets onto castor oil generates stable spherical gold nanoparticles (AuNPs) of 2.4 to 3.8 nm. The AuNP size increases with the discharge voltage and the mechanism of nucleation and growth are related to the energy of the atoms/clusters ejected from the target.