Microemulsions as Reaction Media for the Synthesis of Bimetallic Nanoparticles: Size and Composition of Particles

This paper describes the synthesis of intermetallic Pt/Bi and Pt/Pb nanoparticles (NPs) using water-in-oil (w/o) microemulsions (μe) as template. For that purpose, w/o-microemulsions containing H 2 PtCl 6 + Pb(NO 3 ) 2 and H 2 PtCl 6 + Bi(NO) 3, respectively, were mixed either with a w/o-microemulsion containing the reducing agent (NaBH 4 ) or with solid NaBH 4 . A variation of the amount of reducing agent led to different particle compositions and sizes, while different ratios of the two metal salts only affected the composition but not the size of the resulting NPs. The size and structure of the microemulsion droplets were studied via small angle X-ray scattering (SAXS), and the intermetallic NPs were characterized by high resolution transmission electron microscopy (HRTEM) in combination with energy dispersive X-ray spectroscopy (EDX) and selected area electron diffraction (SAED). The results revealed that it is indeed possible to synthesis Pt/Pb and Pt/Bi intermetallic nanoparticles of ∼3−8 nm in diameter at low temperatures.