Permanent magnetism in phosphine- and chlorine-capped gold: from clusters to nanoparticles
Magnetometry results have shown that gold NPs (∼2 nm in size) protected with phosphine and chlorine ligands exhibit permanent magnetism. When the NPs size decreases down to the subnanometric size range, e.g. undecagold atom clusters, the permanent magnetism disappears. The near edge structure of the X-ray absorption spectroscopy data points out that charge transfer between gold and the capping system occurs in both cases. These results strongly suggest that nearly metallic Au bonds are also required for the induction of a magnetic response. Electron paramagnetic resonance observations indicate that the contribution to magnetism from eventual iron impurities can be disregarded.
KeywordsGold clusters Gold nanoparticles EPR spectroscopy SQUID magnetometry Ferromagnetic behaviour
The authors would like to acknowledge the support of the European Synchrotron Radiation Facility and BM29 beamline staff. This research has been supported by the Spanish Ministry of Science ‘Ministerio de Ciencia e Innovación (MICINN)’ (Strategic Action NAN2004-09125-C07) and the Andalusian Government ‘Junta de Andalucía’ (Excellence Project P06-FQM-02254 and P09-FQM-4554, group TEP127). M.A. Muñoz-Márquez thanks the Spanish Research Council ‘Consejo Superior de Investigaciones Científicas (CSIC)’ I3P programme, E. Guerrero acknowledges the MICINN for financial support and R. Lucena thanks CSIC for a PhD grant.
- Braunstein P, Lehner H, Matt D, Burgess K, Ohlmeyer MJ (1990) Inorganic Syntheses, vol 27, chap 5: transition metal cluster complexes. Wiley InterScience, Malden. Section 42, A platinum-gold cluster: chloro-1 κ C l-bis(triethylphosphine-1κP)bis(triphenyl-phosphine)- 2κP, 3κP-triangulo-digold-platinum(1+) trifluoromethanesulfonate, pp 218–221Google Scholar
- Briant CE, Theobald BRC, White JW, Bell LK, Mingos DMP (1981) Synthesis and X-ray structural characterization of the centered icosahedral gold cluster compound [Au13(PMe2Ph)10Cl2](PF6)3: the realization of a theoretical prediction. J Chem Soc Chem Commun (5):201–202Google Scholar
- Brust M, Walker M, Bethell D, Schiffrin DJ, Whyman R (1994) Synthesis of thiol-derivatised gold nanoparticles in a two-phase liquid–liquid system. J Chem Soc Chem Commun, p 801Google Scholar
- de la Venta J, Bouzas V, Pucci A, Laguna-Marco MA, Haskel D, te Velthuis SGE, Hoffmann A, Lal J, Bleuel M, Ruggeri G, de Julián Fernández C, García MA (2009) X-ray magnetic circular dichroism and small angle neutron scattering studies of thiol capped gold nanoparticles. J Nanosci Nanotech 9:6434–6438CrossRefGoogle Scholar
- Garitaonandia JS, Insausti M, Goikolea E, Suzuki M, Cashion JD, Kawamura N, Ohsawa H, Gil de Muro I, Suzuki K, Plazaola F, Rojo T (2008) Chemically induced permanent magnetism in Au, Ag and Cu nanoparticles: localization of the magnetism by element selective techniques. Nano Lett 8(2):661–667CrossRefPubMedADSGoogle Scholar
- Menard LD, Gao SP, Xu H, Twesten RD, Harper AS, Song Y, Wang G, Douglas AD, Yang JC, Frenkel AI, Nuzzo RG, Murray RW (2006a) Sub-nanometer Au monolayer-protected clusters exhibiting molecule-like electronic behavior: quantitative high-angle annular dark-field scanning transmission electron microscopy and electrochemical characterization of clusters with precise atomic stoichiometry. J Phys Chem B 110(26):12874–12883CrossRefPubMedGoogle Scholar
- Menard LD, Xu H, Gao SP, Twesten RD, Harper AS, Song Y, Wang G, Douglas AD, Yang JC, Frenkel AI, Murray RW, Nuzzo RG (2006b) Metal core bonding motifs of monodisperse icosahedral Au13 and larger Au monolayer-protected clusters as revealed by X-ray absorption spectroscopy and transmission electron microscopy. J Phys Chem B 110(30):14564–14573CrossRefGoogle Scholar
- Mingos DMP (1976) Molecular-orbital calculations on cluster compounds of gold. J Chem Soc Dalton Trans (13):1163–1169Google Scholar
- Mingos DMP (1996) Gold—a flexible friend in cluster chemistry. J Chem Soc Dalton Trans (5):561–566Google Scholar
- Nunokawa K, Onaka S, Ito M, Horibe M, Yonezawa T, Nishihara H, Ozeki T, Chiba H, Watase S, Nakamoto M (2006) Synthesis, single crystal X-ray analysis, and TEM for a single-size Au11 cluster stabilized by SR ligands: the interface between molecules and particles. J Organomet Chem 691:638–642CrossRefGoogle Scholar