Control synthesis of magnetic Fe(3)O(4)-chitosan nanoparticles under UV irradiation in aqueous system

Novel magnetic Fe(3)O(4)-chitosan nanoparticles were synthesized via photochemical method in an emulsifier-free aqueous system at room temperature for the first time. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results showed that the Fe(3)O(4)-chitosan nanoparticles were in regular shape with a mean diameter of 41 nm, whereas the average size in aqueous solution measured by photocorrelation spectroscopy (PCS) was 64 nm, which indicated that the nanoparticles had water-swelling properties. X-ray diffraction (XRD) patterns indicated that the Fe(3)O(4) nanoparticles were pure Fe(3)O(4) with a spinel structure, and the irradiation under UV light did not result in a phase change. The Fe(3)O(4)-chitosan nanoparticles were also characterized by Fourier transform infrared (FTIR) spectra, thermogravimetric analysis (TGA) and vibrating sample magnetometer (VSM). Magnetic measurement revealed that the saturated magnetization (Ms) of the Fe(3)O(4)-chitosan nanoparticles reached 48.6 emu/g and the nanoparticles showed the characteristics of superparamagnetism. The stability test showed these novel nanoparticles had high magnetic stability. The PCS and TGA results indicated that the size and chitosan content of Fe(3)O(4)-chitosan nanoparticles formed was pH- and chitosan/Fe(3)O(4) ratio-dependent, which could be used to synthesize magnetic Fe(3)O(4)-chitosan nanoparticles with different size to meet the requirements of different applications.