Title: Structural aspects of transition-metal nanoparticles in imidazolium ionic liquids

 

Author: Giovanna Machado, Jackson D. Scholten, Tiago de Vargas, Sergio R. Teixeira, Luiz Henrique Ronchi, Jairton Dupont

 

Address: Laboratory of Molecular Catalysis, Institute of Chemistry, IQ-UFRGS Av. Bento Goncalves 9500, P.O. Box 15003, 91501-970, Porto Alegre, RS, Brazil. ' Laboratory of Molecular Catalysis, Institute of Chemistry, IQ-UFRGS Av. Bento Goncalves 9500, P.O. Box 15003, 91501-970, Porto Alegre, RS, Brazil. ' Department of Geology, IG-UFRGS Av. Bento Goncalves 9500, P.O. Box 15001, 91501-970, Porto Alegre, RS, Brazil. ' Laboratory of Thin Films Institute of Physics, IF-UFRGS, Av. Bento Goncalves 9500, P.O. Box 15051, 91501-970, Porto Alegre, RS, Brazil. ' Universidade do Vale do Rio dos Sinos, UNISINOS – PPGEO – Programa de Pos-Graduacao em Geologia, Brazil. ' Laboratory of Molecular Catalysis, Institute of Chemistry, IQ-UFRGS Av. Bento Goncalves 9500, P.O. Box 15003, 91501-970, Porto Alegre, RS, Brazil

 

Journal: Int. J. of Nanotechnology, 2007 Vol.4, No.5, pp.541 - 563

 

Abstract: Imidazolium-based ionic liquids (ILs) display a pronounced self-organisation in the solid, liquid and even in the gas phase. These pre-organised structures are formed mainly through hydrogen bonds between the cations and anions that induce structural directionality. This structural organisation of ILs can be used as 'entropic drivers' for spontaneous, well-defined, and extended ordering of nanoscale structures. Furthermore, these ILs structures can adapt or are adaptable to many species, as it provides hydrophobic or hydrophilic regions and a high directional polarisability which can be oriented parallel or perpendicular to the included species. The formation and stabilisation of transition-metal nanoparticles in 1-n-butyl-3-methyl imidazolium ILs occurs with the re-organisation of the hydrogen bond network and generate nanostructures with polar and non-polar regions where the nanoparticles are included. The IL forms a protective layer surrounding the transition-metal nanoparticles surface with an extended molecular length of around 2.8–4.0 nm depending on the type of anion suggesting the presence of semi-organised anionic species composed of supramolecular aggregates of the type [(BMI)x–n(X)x]n−. This structural organisation is similar to that already observed in solid, liquid, gas phase and in solution of imidazolium ILs. This protective layer is probably composed of imidazolium aggregate anions located immediately adjacent to the nanoparticle surface – providing the Coulombic repulsion – and counter-cations that provide the charge balance.

 

Keywords: transition metals; nanoparticles; imidazolium ionic liquids; DRX; POM; SAXS; TEM; nanotechnology; self-organisation; nanostructures.

 

DOI: 10.1504/IJNT.2007.014809

10.1504/07.14809

 

 

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