An Investigation of Magnetic and Fluorescent core-shell CdTe/Fe3O4 nano-composites

The magnetic nanoparticles with luminescent properties make the marker and separation work further convenient in the biological fields, such as bio-imaging, bio-labeling, bio-medicine, bio-treatment, etc. In the current research, a multifunctional nanoparticles with a magnetic Fe3O4 core and a CdTe quantum dots (QDs) shell of was prepared via self-assembling method and characterized via transmission electron microscopy (TEM), ultraviolet spectrum (UV), and fluorescence spectrum (FS). Magnetic Fe3O4 nanoparticles were firstly prepared by chemical precipitation method with sodium hydroxide as precipitant at 50 degrees C, well dispersed Fe3O4 nanoparticles in size of 10 nm were observed via TEM and were use as core. The synthesized CdTe QDs were surface modified with 2-mercaptopropionic acid and the magnetic core-shell CdTe/Fe3O4 nanoparticles were constructed by the formation of electrovalent bond between -NH3+ and -COO-. The prepared core-shell CdTe/Fe3O4 nanoparticles can be simply separated or precipitated from the reactant solution. The factors influencing the properties of nanoparticles were investigated, including mol ratio of Fe3O4:CdTe, refluxing time, reacting temperature, and pH value etc. The results indicated the core-shell CdTe/Fe3O4 nanoparticles with excellent magnetic and fluorescent properties can be achieved when the mol ratio of Fe3O4:CdTe is 1:3, and pH was set at 6.0, refluxed for 0.5h at 30 degrees C. 15nm of average size of the CdTe/Fe3O4 nanoparticles was confirmed with TEM. The red shift of maximum emission wavelength from 530 nm to 570 nm and maximum absorbance wavelength from 530 nm to 535 nm were determined via FS and UV, respectively, these data inferred the formation of CdTe shells. The core-shell magnetic and fluorescent CdTe/Fe3O4 nano-composites will be an useful tools in biological, genetics, and bio-pharmic applications.