Direct Synthesis and Size Selection of Ferromagnetic FePt Nanoparticles

A one-step synthesis of L1 0 FePt nanoparticles ca. 17.0 nm in diameter by reductive decomposition of the single-source precursor, FePt(CO) 4 dppmBr 2, on a water-soluble support (Na 2 CO 3 ) is demonstrated. Direct conversion of a FePt(CO) 4 dppmBr 2 /Na 2 CO 3 composite to a L1 0 FePt/Na 2 CO 3 nanocomposite occurs at 600 °C under getter gas with metal-ion reduction and minimal nanoparticle coalescence. Triturating the resulting nanocomposite with water simultaneously dissolves the sodium carbonate solid support and precipitates the formed fct FePt nanoparticles. As-prepared FePt nanoparticles are ferromagnetic and exhibit coercivities of 14.5 kOe at 300 K and 21.8 kOe at 5 K. When capped by functionalized methoxypoly(ethylene glycol) surfactant molecules, as-prepared, polydisperse ferromagnetic FePt nanoparticles can be dispersed and size-selected by fractional precipitation.