Substituent effect of Fe(β-diketonate)₃ on the control of self-assembly FePt-based nanoparticles

Three Fe(β-diketonate)₃ compounds namely Fe(tmhd)₃ (tmhd = 2,2,6,6-tetramethyl-3,5-heptanedionato), Fe(hfac)₃ (hfac = hexafluoroacetylaceto), and Fe(dbm)₃ (dbm = dibenzoylmethane) were used as substitutes to Fe(acac)₃ (acac = acetyleacetonate) in the synthesis of FePt nanoparticles. The obtained superparamagnetic nanoparticles are 4–5 nm in diameter without showing a large size variation with substituent Fe(β-diketonate)₃. The synchrotron X-ray absorption spectroscopy confirmed the energy dispersive spectroscopy that as-synthesized nanoparticles were composed of iron oxides and metallic FePt₃ alloys. By employing Fe(hfac)₃, the Fe fraction was reduced and the magnetization was modest. The use of Fe(dbm)₃ as starting materials gave rise to densely packed FePt₃/Fe₂O₃ heterodimers. The replacements of Fe(acac)₃ by Fe(tmhd)₃ led to the long-range order of nanoparticle assembly with the narrowest size distribution.