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.