Fe3O4 magnetic nanoparticles with mean diameter of about 6 nm coated by PEG4000 were prepared by a precipitation method with ferric chloride and ferrous sulfate as starting materials and ammonia for alkalinizing

and the Fe3O4-PEG4000 magnetic nanoparticles obtained were further modified by citric acid through ultrasonic treatment.Afterwards

NH2 end group surface functionalized Fe3O4 magnetic nanoparticles Fe3O4@SiO2-NH2were prepared through Stober method using silane coupling agent.Further

positively charged ionic polyurethane (IPU) was grafted onto the surface of Fe3O4@SiO2 nanoparticles by polymerization of NH2 end group

presynthesized ionic diol

PEG200 and toluylene-2

4-diisocyanate (TDI).Finally

Fe3O4/CdTe/polyurethane (Fe3O4/CdTe/IPU) nanocomposites were prepared by electrostatic interaction of positively charged IPU and thioglycolic acid coated CdTe quantum dots(QDs).The structure of Fe3O4/CdTe/IPU nanocomposites was characterized and verified by XRD

FTIR

TGA

TEM

VSM

UV and PL analyses.It was found through XRD spectra that Fe3O4/CdTe/IPU nanocomposites were a mixture of cubic-structural Fe3O4 nanoparticles

amorphous SiO2 and cubic-structural CdTe QDs.According to the FTIR analyses

the chemical bonds of SiO2

IPU and Fe3O4 indicated that SiO2 and IPU were grafted onto the surface of Fe3O4 nanoparticles.The results of TGA indicated that the coating amount of IPU was about 40% (W/W).TEM analyses showed that the SiO2 coated Fe3O4 nanoparticles were well dispersed which had a relatively uniform diameter of about 20 nm

and the CdTe QDs were arranged around the magnetic nanoparticles.The hysteresis loops proved the superparamagnetic properties of the as-prepared magnetic nanoparticles and nanocomposites.The UV and PL spectra suggested the nanocomposites revealed the properties of the QDs

and the UV irradiation images showed that the QDs moved and aggregated with magnetic nanoparticles in the magnetic field.