Preparation of polymer-protected NiMoPt alloy nanoparticles dispersible in water over a wide pH range by a hot-soap method and ligand-exchange reaction

Abstract

The reduction of bis(acetylacetonato)platinum(II), nickel(II) acetate tetrahydrate and molybdenum(II) acetate dimer in a mixed solvent of oleylamine and diphenyl ether using 1,2-hexadecanediol resulted in the production of oleylamine-protected ternary alloy nanoparticles (nickel–molybdenum–platinum ternary alloy nanoparticles (NiMoPtNPs)). A ligand-exchange reaction with 50% N-methylated linear poly(ethyleneimine-co-N-methylethyleneimine) (poly(EI-co-NMEI)) in chloroform yielded poly(EI-co-NMEI)-protected NiMoPtNPs. The resultant nanoparticles had average diameters of 1.9–2.5 nm and could be dispersed in water at pH levels ranging from −1 to 14. The average radii of the NiMoPtNPs decreased when the protecting polymer was changed from oleylamine to poly(EI-co-NMEI). Energy-dispersive X-ray spectroscopy of the poly(EI-co-NMEI)-protected NiMoPtNPs was performed to confirm the formation of polymer-protected alloy nanoparticles of nickel, molybdenum and platinum. Novel nickel–molybdenum–platinum ternary alloy nanoparticles (NiMoPtNPs) stabilized by oleylamine were prepared by a hot-soap method. The following ligand-exchange reaction of oleylamine with 50% N-methylated linear poly(ethyleneimine-co-N-methylethyleneimine) (poly(EI-co-NMEI)) provided poly(EI-co-NMEI)-protected NiMoPtNPs. The average radii of poly(EI-co-NMEI)-protected NiMoPtNPs were 1.9–2.5 nm and were decreased as compared with oleylamine-protected NiMoPtNPs. Poly(EI-co-NMEI)-protected NiMoPtNPs were dispersed in methanol, ethanol and water in the range of pH −1 to 14. The energy-dispersive X-ray spectrometric analysis showed that poly(EI-co-NMEI)-protected NiMoPtNPs are a ternary metal alloy.