Characterisation of Mn_0·7Zn_0·3Fe₂O₄ nanoparticles prepared by two stage annealing

Abstract

Nanoparticles of the spinel ferrite Mn_0·7Zn_0·3Fe₂O₄, with potential for use as contrast agents for magnetic resonance imaging applications, have been prepared by a sol–gel method followed by a two stage annealing process. The second stage of the annealing process improved the quality of the nanoparticles but also led to intergrown aggregates. The nanoparticles were milled to reduce this aggregation. After hand milling, the average nanoparticle size was 20 nm and after 5 h ball milling, the average nanoparticle size was 10 nm. The principal objectives of this study were to assess the effects of the two stage annealing process and milling on average nanoparticle size, crystal quality and magnetic properties relating to potential use in magnetic resonance imaging. Preliminary cytotoxicity measurements enabled assessment of possible nanoparticle contamination during milling on potential medical and clinical applications. A special surfactant was modified to disperse the nanoparticles in water and render them hydrophilic and to reduce agglomeration.

Keywords:

• Nanoparticles
• Ferrite
• Relaxivity
• Two stage annealing
• MRI

Special thanks go to the Administration Missions of Libyan High Education for financial support for this research project, and the authors wish to thank Dr Pascal André of the University of St Andrews for assistance with SQUID measurements. The research leading to these results has received funding from the European Community’s Seventh Framework Programme (FP7/2007/2013) under grant agreement number 230674 (Nanoporation project).