title: Stability of sputter-deposited gold nanoparticles in imidazolium ionic liquids.
abstract: The stability of gold nanoparticles synthesised by sputter deposition has been studied in situ in 1-butyl-3-methylimidazolium ionic liquids with bis(trifluoromethylsulfonyl)imide, tetrafluoroborate, hexafluorophosphate and dicyanamide anions with UV-VIS absorption spectroscopy and transmission electron microscopy. Besides the growth of the gold nanoparticles, two other processes were observed after sputtering, namely aggregation and sedimentation of these nanoparticles. To model the absorption spectra of the sputtered gold nanoparticles, generalized multiparticle Mie calculations were performed. These theoretical calculations confirm the increase in absorbance at longer wavelength for larger aggregates and are in agreement with the experimental observations. It was found that the kinetics of aggregation and sedimentation scale with the viscosity of the ionic liquid. Small amounts of water were found to have a large detrimental influence on the stability of the colloidal suspensions of the gold nanoparticles in ionic liquids. From the large discrepancy between the theoretical and the experimentally observed stability of the NPs, it was concluded that structural forces stabilize the gold nanoparticles. This was also borne out by AFM measurements.
authors.affiliation: KU Leuven - University of Leuven, Department of Chemistry, Celestijnenlaan 200F, P.O. Box 2404, B-3001 Heverlee, Belgium.
authors.forename: Evert
authors.initials: E
authors.lastname: Vanecht
authors.forename: Koen
authors.initials: K
authors.lastname: Binnemans
authors.forename: Sergiy
authors.initials: S
authors.lastname: Patskovsky
authors.forename: Michel
authors.initials: M
authors.lastname: Meunier
authors.forename: Jin Won
authors.initials: JW
authors.lastname: Seo
authors.forename: Linda
authors.initials: L
authors.lastname: Stappers
authors.forename: Jan
authors.initials: J
authors.lastname: Fransaer
mesh_terms: D006046:Gold / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry*; D052578:Ionic Liquids / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D013499:Surface Properties; D014867:Water / Q000737:chemistry
chemical_list: C525963:1-butyl-3-methylimidazolium; D007093:Imidazoles; D052578:Ionic Liquids; D014867:Water; D006046:Gold