Synthesis of solid solution and core-shell type cobalt-platinum magnetic nanoparticles via transmetalation reactions

In this article, we report the synthesis of solid solution and core-shell types of well-defined Co-Pt nanoalloys smaller than 10 nm. The formation of these alloys is driven by redox transmetalation reactions between the reagents without the need for any additional reductants. Also the reaction proceeds selectively as long as the redox potential between the two metals is favorable. The reaction between Co(2)(CO)(8) and Pt(hfac)(2) (hfac = hexafluoroacetylacetonate) results in the formation of solid solution type alloys such as CoPt(3) nanoparticles. On the other hand, the reaction of Co nanoparticles with Pt(hfac)2 in solution results in Co(core)-Pt(shell) type nanoalloys. Nanoparticles synthesized by both reactions are moderately monodispersed (sigma < 10%) without any further size selection processes. The composition of the alloys can also be tuned by adjusting the ratio of reactants. The magnetic and structural properties of the Obtained nanoparticles and reaction byproducts are characterized by TEM, SQUID, UV/vis, IR, EDAX, and XRD.