Improvement of the saturation magnetisation using Plackett–Burman design and response surface methodology: superparamagnetic iron oxide nanoparticles synthesised by co-precipitation under nitrogen atmosphere

Abstract

Superparamagnetic iron oxide nanoparticles (SPIONs) are highly promising materials especially for biomedical applications. Under study, Plackett–Burman (PB) design and subsequent response surface methodology (RSM) from design of experiments were successfully employed for the improvement of saturation magnetisation, Ms of SPIONs with zero coercivity, Hc. Regression analysis has also been applied to evaluate the Ms of the SPIONs. Twelve experiments from PB design were conducted on the synthesis of the nanoparticles by co-precipitation under nitrogen atmosphere. The effects of simultaneously varying independent parameters; Fe2+/Fe3+ molar ratio (MR), total iron ion concentration (TIC), base concentration (BC), reaction time (RTi), stirring rate (SR), and reaction temperature (RTe) on maximum Ms response with zero coercivity, Hc were studied with the RMS. The most effective and interactive factor for maximum Ms with zero Hc is found to be the MR. Characterisations of the nanoparticles were performed by vibrating sample magnetometry, X-ray diffraction technique and Fourier transform infrared spectroscopy. After experimental process optimisation, the Ms of the synthesised SPIONs were increased from 52.6 to 67.2 emu/g with zero Hc. The optimal sample was also shown to be iron oxide with the crystallite size of 10 nm. The linear regression was successfully estimated the Ms value (66.7 emu/g) using optimal conditions. The experimental results and predicted values were found to be very close to each other. The results demonstrated that optimal values for the synthesis parameters can be efficiently used for the synthesis of SPIONs with maximum Ms.