| Nanoparticles have unique, size-dependent properties. In addition, magnetic nanoparticles have been of great interest for biomedical applications including magnetic resonance imaging, bio-separation, and hyperthermia treatment. Nevertheless, the reactivity of magnetic nanoparticles has been shown to greatly increase as the particle dimensions are reduced, and particles with relatively small sizes may undergo rapid degradation when they are directly exposed to certain environments. Consequently, a suitable coating is essential to overcome such limitations. Quantum dots (QDs), which have excellent optics function, have gained extensive attention due to their potential applications as labeling agents for biological research. The fabrication of bifunctional magnetic-luminescent composite microspheres for practical use in a wide range of applications from medicine and biotechnology to electronics and catalysis is currently of considerable interest. The encapsulation of magnetic and optical materials within a carrier polymer (silica) based nanoparticle is seen as a significant and important innovation. However, a common problem encountered when applying these magnetic-luminescent silica composite microspheres is their poor magnetic response due to the low loading density of magnetic nanoparticles, which makes the recovery of magnetic-luminescent silica composite microspheres much more time-consuming and even impractical.In this paper, we have prepared magnetic-luminescent composite microspheres with a high saturation magnetization via three consecutive steps by microemulsion combined with a modified StOber method and the layer-by-layer (LbL) assembly technique. The results of this work are as following:(1) CdSe quantum dots were prepared with precursors Na2SeSO3 in aqueous solution and the fluorescent properties of CdSe QDs with different experimental condition were discussed. The products were of monodispersed, and uniform in radius, size controllable. The methods are easy to handle, low in price, with good repeatability and environmental friendly.(2) (Ni,Zn)Fe2O4 nanoparticles were prepared via the thermal decomposition of precursors in the open air with octadecylamine as capping agent and the influence of different experimental condition on the magnetic properties of the products was researched. The product has good dispersion, and size for 10 nm around, with a narrow size distribution.(3) This paper selects a new microemulsion system with diethylene glycol as continuous phase, toluene as oil phase and TX-100 as surfactant. Water instead by diethylene glycol as continuous phase can limit the hydrolysis and condensation of TEOS in small droplets, through improving amount of magnetic materials in the droplets, high magnetic response silica microspheres will synthesised. After the surface modification of magnetic microsphere by silane coupling agent, quantum dot decorate the magnetic microsphere surface via electrostatic self-assembly. StOber method is in magnetic nanoparticles surface modification with SiO2 by organo-siloxane catalyzed by ammonia in ethanol and water mixed solvents. In this paper, the magnetic nanoparticles were replaced by magnetic microspheres, and add quantum dot, through the control of alcohol, ammonia water quantity and so on, magnetic fluorescence composite microspheres were synthesis. Magnetic-luminescent composite microspheres with high saturation magnetization was obtained by assembling CdSe onto the surface of magnetic silica microspheres. TEM, HRTEM, FT-IR, PL and VSM were used to investigate the morphology and properties of the composite microspheres. The results showed that the composite microspheres displayed a strong magnetic behavior at room temperature. The as-synthesized composite microspheres exhibit a much higher saturation magnetization because of the high loading density of (Ni,Zn)Fe2O4 magnetic material compared to others reported in the current literature. Therefore, the composite microspheres is expected to find many potential applications in biomedical fields.
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