Naked metal nanoparticles from metal carbonyls in ionic liquids: Easy synthesis and stabilization

• Published in: Coordination chemistry reviews 2011-09, Vol.255 (17), p.2039-2057
• Main Authors: Vollmer, Christian, Janiak, Christoph
• Format: Article
• Language: English
• Subjects: Catalysis; Ionic liquid; Metal carbonyl; Metal nanoparticle; Stabilization; Synthesis
• ISSN: 0010-8545; 1873-3840
• DOI: 10.1016/j.ccr.2011.03.005

[Display omitted] ► Commercial metal carbonyls M x (CO) y are elegant metal-nanoparticle (M-NP) precursors. ► No extra reducing agent is necessary to obtain M-NPs from metal carbonyls. ► Electrostatic properties of ionic liquids (ILs) allow for the stabilization of M-NPs. ► Stabilization of M-NPs in ILs without additional capping ligands. ► Easy and rapid microwave induced decomposition of metal carbonyls M x (CO) y in ILs. An overview with more than 160 references on the synthesis and stabilization of metal nanoparticles (M-NPs) from metal carbonyls, metal salts in ionic liquids (ILs) and in particular from metal carbonyls in ionic liquids is given. The synthesis of M-NPs can proceed by chemical reduction, thermolysis, photochemical decomposition, electroreduction, microwave and sonochemical irradiation. Commercially available metal carbonyls M x (CO) y are elegant precursors as they contain the metal atoms already in the zero-valent oxidation state needed for M-NPs. No extra reducing agent is necessary. The side product CO is largely given off to the gas phase and removed from the dispersion. The microwave induced thermal decomposition of metal carbonyls M x (CO) y in ILs provides an especially rapid and energy-saving access to M-NPs because of the ILs significant absorption efficiency for microwave energy due to their high ionic charge, high polarity and high dielectric constant. The electrostatic and steric properties of ionic liquids allow for the stabilization of M-NPs without the need of additional stabilizers, surfactants or capping ligands and are highlighted by pointing to the DLVO (Derjaugin–Landau–Verwey–Overbeek) and extra-DLVO theory. Examples for the direct use of M-NP/IL dispersions in hydrogenation catalysis of cyclohexene and benzene are given.