Fabrication of naked silver nanoparticles in functionalized ionic liquids

Confined Silver Nanoparticles in Ionic Liquid Films

This work reports the formation of silver nanoparticles (AgNPs) by sputter deposition in thin films of three different ionic liquids (ILs) with the same anion (bis(trifluoromethylsulfonyl)imide) and cation (imidazolium), but with different alkyl chain lengths and symmetries in the cationic moiety ([C4C1im][NTf2], [C2C2im][NTf2], and [C5C5im][NTf2]). Ionic liquid (IL) films in the form of microdroplets with different thicknesses (200 to 800 monolayers) were obtained through vacuum thermal evaporation onto glass substrates coated with indium tin oxide (ITO). The sputtering process of the Ag onto the ILs when conducted simultaneously with argon plasma promoted the coalescence of the ILs’ droplets and the formation, incorporation, and stabilization of the metallic nanoparticles in the coalesced IL films. The formation/stabilization of the AgNPs in the IL films was confirmed using high-resolution scanning electron microscopy (SEM) and UV-Vis spectroscopy. It was found that the IL films with larger thicknesses (600 and 800 monolayers) were better media for the formation of AgNPs. Among the ILs used, [C5C5im][NTf2] was found to be particularly promising for the stabilization of AgNPs. The use of larger IL droplets as capture media was found to promote a better stabilization of the AgNPs, thereby reducing their tendency to aggregate.

Sputtering onto liquids: a critical review

Sputter deposition of atoms onto liquid substrates aims at producing colloidal dispersions of small monodisperse ultrapure nanoparticles (NPs). Since sputtering onto liquids combines the advantages of the physical vapor deposition technique and classical colloidal synthesis, the review contains chapters explaining the basics of (magnetron) sputter deposition and the formation of NPs in solution. This review article covers more than 132 papers published on this topic from 1996 to September 2021 and aims at providing a critical analysis of most of the reported data; we will address the influence of the sputtering parameters (sputter power, current, voltage, sputter time, working gas pressure, and the type of sputtering plasma) and host liquid properties (composition, temperature, viscosity, and surface tension) on the NP formation as well as a detailed overview of the properties and applications of the produced NPs.

Functionalized Ionic Liquids Sputter Decorated with Pd Nanoparticles

The fabrication of surface clean palladium nanoparticles of 3–4nm was accomplished in imidazolium-based functionalized ionic liquids (ILs) having methoxy, cyano, and thio groups by magnetron sputtering deposition. The size of the NPs was strongly dependent on the surface composition and/or organisation of the ILs. The NP growth apparently occurred preferentially in the bulk of the fluids, whereas nucleation apparently occurred preferentially at the IL surface. Smaller NPs were detected close to the methoxy containing IL surface and were covered by at least one layer of IL ion pairs, as revealed by high-sensitivity low-energy ion scattering (HS-LEIS) measurements.

Rapid Assessment of Sputtered Nanoparticle Ionic Liquid Combinations

A high-throughput method is presented for the efficient assessment of the formation and stability of nanoparticle suspensions in ionic liquids which differ in their cations and anions. As a proof of principle, Ag was sputtered on a cavity array filled with 9 different ionic liquids. Not all nanoparticle ionic liquid combinations form a stable suspension with separated nanoparticles. Directly after synthesis, the formation of nonagglomerated nanoparticle suspensions with sizes from 4 to 9 nm is observed by transmission electron microscopy as well as different time dependencies of the suspension stabilities. Only 3 out of the tested 9 nanoparticle ionic liquid suspensions show long-term stability: Stable suspension of spherical nanoparticles are formed in the ionic liquids 1-butyl-3-methylimidazolium bis(perfluoroethylsulfonyl)imide [Bmim][(Pf)₂N], 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [Bmim][(Tf)₂N], and 1-butyl-1-methylpyrrolidinum bis(trifluoromethylsulfonyl)imide [BmPyr][(Tf)₂N].