A synthesis of polyethylene glycol (PEG)-coated magnetite Fe3O4 nanoparticles and their characteristics for enhancement of biosensor

The magnetite Fe3O4 nanoparticles were synthesized by using chemical co-precipitation method and these nanoparticles were successfully coated by polyethylene glycol (PEG) with variation concentrations of PEG. The magnetite Fe3O4 nanoparticles used as a bimolecular label (nano-tags), exhibiting a soft magnetic behavior with magnetization (Ms) of 77.16 emu g−1 and coercivity (Hc) of 50 Oe respectively. The polyethylene glycol (PEG) was used as a biocompatible polymer. The x-ray diffraction (XRD) patterns of the Fe3O4 showed that Fe3O4 was well crystallized. It also confirmed the existence of invers spinel. The diffraction peak of 35.4° was used to calculate the crystallite size. The estimation of Fe3O4 average crystallite size is 12 nm, while the PEG-coated Fe3O4 nanoparticles is 8.6 nm. The transmission electron microscopy (TEM) images of Fe3O4 showed that the morphology of magnetite Fe3O4 nanoparticle is spherical in shape with uniform grain size and good dispersibility despite the agglomeration it found in some place. The addition of PEG can decrease the agglomeration and reduce the particle size. The existence of PEG layer on Fe3O4 was confirmed by Fourier transform infrared (FTIR) spectroscopy. The result of Vibrating Sample Magnetometer (VSM) showed that saturation magnetization (Ms) of Fe3O4 nanoparticles decreased from 77.16 to 37.15 emu g−1 with the increase of PEG weight from 0% to 50%. Such Fe3O4 nanoparticles with favorable size and tunable magnetic properties are promising biosensor applications.