S 800

The worn surfaces of a representative specimen in each group after 40,000 cycles were observed using a scanning electron microscope (SEM, S-800, Hitachi Corp., Tokyo, Japan) at ×40 and ×5,000 magnification.

For scanning electron microscopy (SEM) analysis, the specimens were fixed in phosphate-buffered saline containing 2% glutaraldehyde and 0.1% paraformaldehyde for 2 h. Then, they were stained with 1% OsO4. Specimens were coated with gold using an EiKO IB-3 ion sputter coater (EiKO, Shawnee, KS, USA) and examined with a field emission gun (FEG) scanning electron microscope (S-800, Hitachi, Japan) at an acceleration voltage of 20 kV. Images were processed with ESCAN 4000 software (Bummi Universe Co., Ltd., Seoul, Korea). For cell length measurements, more than 100 straight-lined cells were chosen randomly from digitized SEM images, and the distance between the two poles of each cell was automatically calculated.

The morphology of all investigated uncoated and coated SPIONs was determined by scanning electron microscopy (SEM-JEOL, JXA-840A Electron Probe Micro-Analyzer, Japan). Energy-dispersive X-ray (EDX) spectroscopy was applied on an SEM-field emission microscope (Hitachi S-800, Oxford, USA) to assess the atomic concentration of various elements on the top surface of the considered samples. Confirmation of the nanostructure was performed using a transmission electron microscope (TEM, JEOL, Japan). X-ray diffraction analysis was used to determine the crystalline phases of the magnetite and their coated nanoparticles using a Bruker diffractometer (Bruker D8 advance, Germany). The patterns were run with a CuKa1 target with a second monochromator 40 kV, 40 mA. The molecular structure was studied qualitatively using a Fourier transform infrared spectroscopy (FTIR) (6100 JASCO) in the range of 4000–400 cm⁻¹. A vibrating sample magnetometer (VSM), (LakeShore 7400; Chicago, IL, USA) was used to investigate the magnetic properties of the magnetite nanoparticles at 300K.