S Pyrpassopoulos et al 2007 Nanotechnology 18 485604 doi:10.1088/0957-4484/18/48/485604
S Pyrpassopoulos1, D Niarchos2, G Nounesis1, N Boukos2, I Zafiropoulou1 and V Tzitzios2,3
Show affiliationsMonodisperse (diameter 10 nm) Au nanoparticles have been synthesized by the reduction of AuCl3 at high temperatures, in commercial oleyl amine, in the presence of tri-octyl phosphine oxide (TOPO). The oleyl amine molecule has multiple roles, acting as high-boiling-point solvent, capping agent and reducing agent. The Au nanocrystalline particles have been studied by powder x-ray diffraction (XRD) and transmission electron microscopy (TEM). The nanoparticles can disperse well in non-polar solvents such as hexane, toluene and chloroform. The as-received Au nanoparticles, capped with the alkylamine-TOPO molecules, form two-dimensional superlattices via solvent evaporation. Moreover, they can be converted into a water-soluble derivative via a simple procedure based on the formation of a physisorbed layer of an ionic (cationic or anionic) surfactant around the capped surface. The charged particles can assemble in aqueous solution into three-dimensional structures via electrostatic interactions.
81.16.Be Chemical synthesis methods
81.07.Bc Nanocrystalline materials
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
Soft matter, liquids and polymers
Surfaces, interfaces and thin films
Issue 48 (5 December 2007)
Received 17 May 2007, in final form 8 October 2007
Published 1 November 2007
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