Chemical transformation from FePt to Fe_1-xPtM_x (M = Ru, Ni, Sn) nanocrystals by a cation redox reaction: X-ray absorption spectroscopic studies

New ternary metal nanocrystals of Fe_1-xPtM_x (M = Ru³⁺, Sn²⁺, or Ni²⁺) were synthesized by chemical transformation from FePt nanocrystals using a cation redox reaction in a solution. The structure and composition of resulting nanocrystals were characterized by high-resolution transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and X-ray photoemission spectroscopy (XPS). Moreover, X-ray absorption near-edge spectroscopy (XANES) was employed to confirm the chemical transformation from FePt to Fe_1-xPtRu_x nanocrystals. The analyses of extended X-ray absorption find structure (EXAFS) revealed the detailed binding structures and coordination numbers of both FePt and Fe_1-xPtRu_x nanocrystals. The results suggested that iron atoms of FePt lattices were oxidized to be Fe²⁺ and Fe³⁺ ions and were replaced by ruthenium atoms from the reduction of Ru³⁺ ions in solution to form Fe_1-xPtRu_x lattices. Our method has opened a new route to easily and rapidly prepare a solid-solution type of ternary metal nanocrystals for catalytic applications.