| With the development of modern technology, the applications of nanotechnology in thebiomedical fields are becoming more and more widely, especially that quantum dots andFe3O4magnetic nanocrystals in the biological markers and the bioseperation. The bifunctionalnanocomposite which combines the quantum dots and Fe3O4magnetic nanocrystals play animportant role in the tumor cells marker, collection and separation. However, there are someproblems limiting its application in the biomedical field. For example, the biological toxicityof the commomly used quantum dots containing Cd （CdS, CdTe, CdSe） is a problem; Thefluorescence intensity has been reduced greatly due to the fluorescence quenching of themagnetic nanoparticles when connected the quantum dots and the Fe3O4magneticnanocrystals directly. Therefore, our work is to solve these problems so as to lay a solidfoundation for biomedical applications. We have been successfully prepared theFe3O4/ZnSe/SiO2/ZnSe fluorescent-magnetic multifunctional nanoparticles through combining theSiO2-coated Fe3O4nanoparticles and nontoxic luminous ZnSe quantum dots.In this paper, the Fe3O4/ZnSe/SiO2core/shell magnetic nanoparticles were synthesized via themodified St ber method by coated SiO2shell on the surface of Fe3O4magnetic nanoparticles.The molar ratio of the reactants, the ethanol/water ratio, the amount of ammonia and thereaction time, which have influence on the magnetic property of the Fe3O4, were investigatedin the experiment firstly. The results showed that the Fe3O4/ZnSe/SiO2had good structure and betterproperty under these conditions:（TEOS）:n（Fe3O4）was5:1, the ethanol/water ratio was3:1,the amount of ammonia was2mL（0.026mol）, and the reaction time was3h. The core/shellstructure was confirmed by several different analysis, like X-ray diffraction analysis （XRD）,transmission electron microscopy analysis （TEM）, scanning electron micrographs and EDSspectrum analysis, infrared spectroscopy analysis, different theimal curve analysis andhysteresis loop analysis.Secondly, the fluorescent magnetic bifunctional nanocomposites were obtained bycombined the ZnSe quantum dots and Fe3O4/ZnSe/SiO2magnetic nanoparticles on the basis ofchemical bonding mechanism. On the basis of ZnSe quantum dots, the carboxyl which wereexposed on the surface of ZnSe quantum dots were activated by1-（3- dimethylamino-propyl）-3-ethoxycarbonyl carbodiimide hydrochloride （EDC） andN-hydroxy succinimide（Sulfo-NHS）. At the same time,3-aminopropyl triethoxysilane（APTES） were introduced into the Fe3O4/ZnSe/SiO2core/shell nanoparticles, and the hydroxylgroups were instead by amino groups. So the chemical bonds were formed by carboxyl andamino groups to link the ZnSe quantum dot and the Fe3O4/ZnSe/SiO2core/shell nanoparticles. Thereaction factors such as the molar ratio of the reactants, reaction time and reaction temperaturewhich played important roles on the fluorescent properties of the Fe3O4/ZnSe/SiO2/ZnSefluorescent/magnetic nanocomposites were investigated by the fluorescence spectra. Theresults showed that the optimal parameters for Fe3O4/ZnSe/SiO2/ZnSe were the following: themolar ratio（ZnSe:Fe3O4/ZnSe/SiO2） was24:1, the tempreture was35℃, the reaction time was1h.Then, the structure and the composition were characterized and analyzed by the XRD and theTEM. And the fluorescent property were discussed by the fluorescence spectroscopy andUV-visible absorption spectroscopy. The magnetic property were characterized by thehysteresis loop. At last, on this basis, the pH value of the buffer solution which had influenceon the properties were investigated. When the pH value was9.0, the flourescent property wasmore stable, and the Fe3O4/ZnSe/SiO2/ZnSe fluorescent/magnetic nanocomposites were held atroom temperature for2weeks.Finally, a preliminary discussion about the on the Fe3O4/ZnSe/SiO2/ZnSe fluorescent/magneticnanocomposite sythesised by inverse microemulsion method were studied, and the effects ofthe components of microemulsion volume ratio, reaction time and reaction temperature on theproperties were discussed. The results showed that, when the reverse phase microemulsionvarious components of the volume of V （TritonX-100）: V （hexanol）: V （cyclohexane）=1:2:5, reaction time and reaction temperature of1, and35℃, the Fe3O4/ZnSe/SiO2/ZnSeparticles composite were displayed good flourescnt and magnetic properties. Through theTEM analysis, fluorescence spectroscopy and UV-visible spectroscopy analysis, magneticanalysis and the digital photographs, we can know that the mechanism of the reaction timeand the reaction tempertute was the same to that no matter in the water solution or in themicroemulsion. And the obtained products were proved to Fe3O4/ZnSe/SiO2/ZnSefluorescent/magnetic bifunctional nanocomposites. |
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