Magnetic and fluorescent inorganic nanoparticles were particularly important due to their broad and potential applications,and multifunctional nanoparticles with magnetic and fluorescent properties were exceptionally expected.The current research introduced CdTe@Fe3O4 multifunctional nanoparticles which combined both magnetic and fluorescent properties in one entity.The CdTe@Fe3O4 nanoparticles were primarily prepared with layer-by-layer (LBL) self-assembly process,and its properties and applications were investigated and discussed in detail.Nano-sized magnetic Fe3O4 were firstly prepared by co-precipitation method in aqueous phase with NaOH as precipitator under the optimum conditions of 50 ℃,Fe2+/Fe3+was 1/2 (mol ratio) for 30min,and then were surfacely modified with 1,6-hexylenediamime.The average size of the particles prepared by the method was about 10 nm observed via transmission electron microscopy (TEM).The core-shell magnetic quantum dots (mQDs),i.e.CdTe@Fe3O4,were prepared by LBL with Fe3O4 nanoparticles as core.The resulting data indicated that the qualified mQDs could be achieved under the optimum conditions when mol ratio of Fe3OdCdTe was 1/3,pH at 6.0,the temperature was set at 30 ℃,and reactant solution was refluxed for 30 min.The obtained mQDs were characterized by transmission electron microscopy (TEM),ultraviolet spectrum (UV),and fluorescence spectrum (FS),respectively.TEM image indicated 12-15 nm of mQDs were obtained,and FS and UV data showed red shift of maximum emission wavelength from 530 nm to 570 nm and maximum absorbance wavelength from 530 nm to 535 nm,respectively,which inferred the successful formation CdTe shell on the surface of magnetic Fe3O4 core.The synthesized mQDs can be conveniently applied in DNA labeling,sensing,and separating process.