Study On Preparation High Performance Magnetic Fe₃O₄ Nanocrystals

Magnetic Fe3O4 nanoparticles were widely applied on many biomedical fields like MRI, magnetic separation, drug carriers, magnetic fluid hyperthermia due to their unique superparamagnetism, high coercivity, low biotoxicity etc. Smaller size, more regular morphology,higher saturation magnetization, temperature elevation under alternating magnetic field, surface modifications improving the biological compatibility and multi-functionalization get the magnetic Fe3O4 better effects in biomedical fields.This thesis mainly focused on three aspects of the high performance, (1) size and morphology, (2) magnetic properties and (3) surface modification and multi-functionalization, each of them was studied under different reactive conditions. The main research and results are as follows.1. To study the size and morphology of themagnetic Fe3O4 nanoparticles synthesized via the high temperature thermal decomposition method, dose of oleic acid and oil amine, nucleation temperature, nucleation time and curing time were discussed. The size and morphology of the resulting magnetic Fe3O4 nanoparticles were characterized by TEM and two kinds of magnetic Fe3O4 nanoparticles with small sizes and remarkable morphologies were chosen for the subsequent research. The synthesis conditions are:(1)12 mmololeic acid and 6 mmoloil amine, nucleating for 60 min at 220℃ and curing for 40 min, the average size of the resulting magnetic Fe3O4 nanoparticles was 15.02 nm, and the morphology was polygonal. (2) 6mmololeic acid and 18mmoloil amine, nucleating for 60 min at 220℃ and curing for 30 min, the average size of the resulting magnetic Fe3O4 nanoparticles was 7.45 nm and the morphology was spherical.2. The magnetic properties of the selectedtwo kinds of magnetic Fe3O4 nanoparticles were studied via changing the nucleation temperature, nucleation time and curing time. Their saturation magnetization and temperature elevation were discussed in details. We found that magnetic Fe3O4 nanoparticles synthesized using 6 mmol oleic acid and 18 mmol oil amine, nucleated for 60 min at 220 ℃ and cured for 30 min have the optimal overall performance. Thesemagnetic Fe3O4 nanoparticles have an average size of 7.45 nm and present spherical morphology. Theirsaturation magnetization66.72emu/g, SAR value was 38.51w/g, in alternating magnetic field when the frequency and current intensity were set as 780 kHz and 12A.3. The study was around surface modification and multi-functionalization of magnetic Fe3O4 nanoparticles. The optimized oil-solublemagnetic Fe3O4 nanoparticles was chosen to modify with CTAB(cetyltrimethyl ammonium bromide), silica and aluminumhydroxide, which gave them excellent water solubility, MRI imaging ability and high protein adsorption capacity (8.63mg[Protein]/mg[Fe]), all these have laid a solid foundation for the follow-up biomedical applications based on MRI and protein adsorption.