Synthesis and Characterisation of Monodispersed Ferrite Nanoparticles

  • Khadijat Abdulwahab

Student thesis: Phd


The work presented in this thesis reports the use of a series of iron pivalate clusters as single source precursors for the synthesis of colloidal iron oxides, ternary ferrites and quaternary ferrite nanoparticles. The iron pivalate clusters [Fe3O(O2CtBu)6(H2O)3](O2CtBu).HO2CtBu, Fe8(OH)4(O2CtBu)12(OC6H4C6H5)8] and [Fe3O(O2CtBu)6(C5H5N)3] were used to synthesise iron oxide nanoparticles by the hot injection thermolysis method. The effect of reaction time was studied for [Fe3O(O2CtBu)6(H2O)3](O2CtBu).HO2CtBu at 260 °C gave a mixture of maghemite-C (Fe2O3) and magnetite (Fe3O4) for the aliquots withdrawn for reaction times of less than 30 minutes whilst only magnetite was obtained after one hour. The diameters of the nanoparticles increase in the higher boiling point solvent; 4.3 ± 0.4 and 4.9 ± 0.5 nm were produced at 260 °C and 289 °C respectively. Heterometallic pivalate clusters of [Fe2CoO(O2CtBu)6(HO2CtBu)3], [Co4Fe2O2(O2CtBu)10], [Fe2MnO(O2CtBu)6(HO2CtBu)3], [Zn4Fe2O2(O2CtBu)10] and [Fe2NiO(O2CtBu)6(HO2CtBu)3] were used to synthesise cobalt, manganese, zinc and nickel ferrites respectively. Quaternary ferrite was synthesised from the thermolysis of [CrCoFeO(O2CtBu)6(HO2CtBu)3]. TEM showed that highly monodispersed spherical ferrite nanoparticles were obtained using 0.50 mmol precursor concentrations at 260 °C in all cases except for [Co4Fe2O2(O2CtBu)10] for which a nearly monodispersed nanoparticles were produced. The decomposition of precursors at 0.25 mmol at different temperatures revealed that larger ferrites nanoparticles were obtained at higher temperature whilst for cobalt ferrite from [Co4Fe2O2(O2CtBu)10], smaller nanoparticles appeared. In all cases, reaction times of less than 1 hour contain traces of iron oxide whilst only pure binary/quartenary ferrite was obtained after one hour. Magnetic measurements revealed that all the iron oxide and ferrite particles are superparamagnetic at room temperature with high saturation magnetisation values. X-ray Magnetic Circular Dichroism (XMCD) analysis confirmed that in cobalt and nickel ferrite particles, most of the nickel and cobalt cations are in the octahedral site. Water-dispersible magnetite and ferrite (MFe2O4 where M = Co, Ni, Zn, Mn) nanoparticles were synthesised from the iron based pivalate clusters. All the ferrites nanoparticles produced are monodispersed without a further size selection process
Date of Award31 Dec 2013
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorPaul O'Brien (Supervisor)

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