A simple way to obtain high saturation magnetization for superparamagnetic iron oxide nanoparticles synthesized in air atmosphere: Optimization by experimental design

摘要

Orthogonal design technique was applied to obtain superparamagnetic iron oxide nanoparticles with high saturation magnetization, M_s. Synthesis of the nanoparticles were done in air atmosphere according to the orthogonal table L_9 3~4. Magnetic properties of the synthesized nanoparticles were measured by a vibrating sample magnetometer. Structural analysis of the nanoparticles was also carried out by X-ray diffraction technique (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). After the analysis of magnetic data, the optimized experimental parameters were determined as [Fe~(-2)]/[Fe~(-3)]=6/6, iron ion concentration=1500mM, base concentration=6.7 M and reaction time=2 min. Magnetic results showed that the synthesis carried out according to the optimized conditions gave the highest M_s of 69.83 emu/g for the nanoparticles synthesized in air atmosphere. Magnetic measurements at 10 K and 300 K showed the sample is superparamagnetic at room temperature. Structural analysis by XRD, FTIR and selected area electron diffraction showed that the sample had the inverse spinel crystal structure of iron oxide. The particle size of the optimized sample determined from the TEM image is 7.0 ± 2.2 nm. The results indicated that the M_s of superparamagnetic iron oxide nanoparticles can be optimized by experimental design with the suitable choice of the synthesis parameters.