Synthesis and characterization of monolayer-capped PtVFe nanoparticles with controllable sizes and composition

Abstract

The ability to control the size and composition of metal nanoparticles is essential in preparing binary or ternary catalysts. This paper reports the results of an investigation of a core-shell synthesis protocol for the preparation of monolayer-capped ternary platinum-vanadium-iron (PtVFe) nanoparticles with a few nanometers in core sizes. Our approach involves the use of metal precursors, capping agents, and reducing agents in controllable ratios for the reaction in a single organic phase. By manipulating the relative concentration ratios of the metal precursors such as platinum acetylacetonate, vanadyl acetylacetonate, and iron pentacarbonyl, and capping agents such as oleic amine and oleic acids, the core-shell type nanoparticles in which the nanocrystal PtVFe cores are encapsulated with a shell of mixed amine/acid monolayer have been successfully synthesized. The average diameters of the nanocrystalline cores are well controlled between 1.4 and 3.5 nm with high monodispersity (+/- 0.3-0.5 nm). The chemical composition of the nanocrystalline cores is shown to be effectively controllable in the range of Pt (20-40%), V (10-40%), and Fe (40-70%) by manipulating the feeding ratios of the metal precursors. The results of characterizations using TEM, DCP-AES, XRD, FTIR, and TGA techniques are discussed, along with their implications to the exploration of the nanoparticles as fuel cell catalysts.