Ionic Liquids for the Synthesis and Stabilization of Metal Nanoparticles

Abstract

The synthesis and stabilization of metal nanoparticles (M-NPs) from metals, metal salts, metal complexes and metal carbonyls in ionic liquids (ILs) is reviewed. 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. The synthesis of M-NPs in ILs can be carried out by chemical or electroreduction, thermolysis and photochemical methods including decomposition by microwave or sono-/ultrasound irradiation. Gas-phase syntheses can use sputtering, plasma/glow-discharge electrolysis and physical vapor deposition or electron beam and γ-irradiation. Metal carbonyl precursors M x (CO) y contain the metal atoms already in the zero-valent oxidation state needed for M-NPs so that no extra reducing agent is necessary. Microwave-induced thermal decomposition of precursors in ILs is a rapid and energy-saving access to M-NPs because of the significant absorption efficiency of ILs for microwave energy due to their ionic charge, high polarity and high dielectric constant. M-NP/IL dispersions can be applied in catalytic reactions, e. g., in C-C coupling or hydrogenation catalysis.

Controlled metal nanostructures: Fertile ground for coordination chemists

“…Weakly coordinating alcohols [141], [142] or carbohydrates like cyclodextrines [143] can also serve as stabilizers, as well as some solvents such as organic carbonates [144], ionic liquids [145], [146], [147], [148], or polyols [149], [150].…”

High catalytic efficiency of palladium nanoparticles immobilized in a polymer membrane containing poly(ionic liquid) in Suzuki–Miyaura cross-coupling reaction

“…The presence of appropriate stabilizers is necessary to prevent their aggregation, which usually results in loss of activity. The stabilization of MNPs can be accomplished by a steric effect [12], an electrostatic effect [13], a combination of both (electrosteric effect) [14], or a ligand [15].…”

Inorganic Nanomaterials Synthesis Using Ionic Liquids

“…57,92,138,180,181 In analogy to ILCPs, they have been termed ILPs. One of the early ILP examples consists of an alcohol-modified IL, which is able to reduce Au(III) to Au(0).…”