Study On Preparation And Property Of Magnetic Nanoparticles-Fluorescent Quantum Dots Composite Microspheres

Owing to the unique optical properties, quantum dots have found their potential application in biological medical field. Magnetic nanoparticles have open the possibilities of applications because of their special magnetic properties, such as biological separation, drug targeted delivery and magnetic resonance imaging. The magnetic fluorescent/polyelectrolytes multifunctional composite materials which make use of interactions between polyelectrolytes, quantum dots and magnetic nanoparticles possess the properties of polyelectrolytes, as well as special properties of quantum dots and magnetic nanoparticles. The magnetic fluorescent/polyelectrolytes multifunctional composite materials could be use in drug targeted delivery, which can be targeted by a magnetic field and detected by a fluorescence microscope. Moreover, the magnetic fluorescent/polyelectrolytes multifunc-tional composite materials have shown great potential applications in biological labels, biological imaging, biological separation, disease diagnose and therapy. So the study on preparation of composite materials is a very interesting task. The major research work and results in this thesis are listed as following:(1) The water-soluble CdSe/CdS/ZnS core/shell/shell quantum dots are prepared by using trisodium citrate as stabilizer in aqueous solution. The X-ray powder diffraction (XRD), transmission electron microscope(TEM), energy dispersive X-ray spectra analysis(EDX), infrared spectrum(IR), UV-vis absorption spectrum(UV-vis) and fluorescent spectrum(FL) are used to characterize the composition, size, morphology and fluorescence properties of CdSe/CdS/ZnS core/shell/shell quantum dots. The results show that CdSe/CdS/ZnS quantum dots are spherical, belong to the cubic zinc blende structure and have good fluorescent properties with a narrow full width at half maximum (FWHM=54nm), the fluorescence quantum yield can reach up to37.3%.(2) Fe3O4-CdSe/CdS/ZnS magnetic fluorescent chitosan-alginate composite micro-spheres are prepared by using chitosan and sodium alginate as coating material. The XRD, SEM, EDS, IR, FL and VSM are used to characterize the composition, morphology, fluorescence and magnetic properties of microspheres. The results show that the magnetic fluorescent chitosan-alginate composite microspheres are spherical and possess good magnetism and fluorescence.(3) Fe3O4-CdSe/CdS/ZnS magnetic fluorescent chitosan-alginate drug-loading microspheres are prepared by using cefradine as model drug with chitosan and sodium alginate as coating material. The influence of preparation conditions on the drug loading and encapsulation efficiency of the microspheres are investigated, and the magnetic properties, fluorescent properties and controlled drug release of microspheres are also been studied. The results show that the drug loading and encapsulation efficiency of the microspheres could reach up to20.17%and40.84%under the optimal reaction conditions. The as-prepared magnetic fluorescent chitosan-alginate drug-loading micro-spheres exhibit favourable fluorescent and magnetic properties, exhibit definite release of the drug in buffer solution with different pH value and the release rate could be regulated by the pH value.