The present work reports the successful synthesis of biosynthesized iron oxide nanoparticles (Fe3O4-NPs) with the use of non-toxic leaf extract of Neem (Azadirachta indica) as a reducing and stabilizing agent. The successful synthesis was confirmed by infrared spectra analysis with strong peak observed between 400–600 cm−1 that corresponds to magnetite nanoparticles characteristics. X-ray diffraction (XRD) analysis revealed that iron oxide nanoparticles were of high purity with crystalline cubic structure phases in nature. Besides, the average size of magnetite nanoparticles was observed to be 9–12 nm with mostly irregular shapes using a transmission electron microscope (TEM) and was supported by field emission scanning electron microscope (FESEM). Energy dispersive X-ray analysis shown that the elements iron (Fe) and oxygen (O) were present with atomic percentages of 33.29% and 66.71%, respectively. From the vibrating sample magnetometer (VSM) analysis it was proven that the nanoparticles exhibited superparamagnetic properties with a magnetization value of 73 emu/g and the results showed superparamagnetic behavior at room temperature, suggesting potential applications for a magnetic targeting drug delivery system.

In this study, this SiO2 has been coated on the surface of Fe3O4 (Fe3O4@SiO2) by hydrolysis and condensation of tetraethyl orthosilicate (TEOS) under alkaline medium at 80oC. It was found that only 500  mL TEOS is required to obtain the best coated Fe3O4 core structures which has been confirmed from its TEM micrograph. FTIR analyses revealed the formation of Si-O-Si bonds at 1084.2–1101.4 cm-1 hence confirmed that SiO2 has been successfully coated the Fe3O4 core. From the FESEM analyses, the average size of silica was ~ 50 -70 nm.  EDX of the Fe3O4@SiO2 showed that silica had been effectively bonded onto the surface of Fe3O4. The VSM measurements confirmed the superparamagnetic properties of Fe3O4@SiO2 that is desirable for biomedical applications.