Structural, magnetic and Raman study of CoFe2O4@C core–shell nanoparticles

Abstract The synthesis of CoFe2O4@C core–shell nanoparticles (NPs) was performed using a two-step method, including reverse micelle and thermo-chemical vapor deposition (TCVD). The water to surfactant molar ratio (W) was selected as 8 and 10. The diameter and crystallite size of the as-prepared CoFe2O4 NPs were lower than 10 nm. Acetylene gas (C2H2) was used as a carbon precursor and coating was performed for 1, 2, and 3 h. After coating, the core size was below 30 nm and the thickness of the shell was below 8 nm. The composition, structure, and morphology of the fabricated NPs were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDS), and selected area diffraction (SAD) pattern. The vibration sample magnetometer (VSM) was also used to investigate the magnetic properties. It was found that carbon shell has a significant effect on the growth and magnetic properties of the core NPs. To study the coated carbon, micro-Raman spectroscopy was used and it was approved that the deposited carbon consists of graphite, MWCNTs and diamond-like carbon (DLC). By increasing the coating time, the ratio of the amorphous peak intensity to the ordered peak intensity I D I G was decreased, causing to an enhancement in the crystalline size of graphite.