摘要
纳米复合材料在现代科学技术中起到了重要的作用，而结合磁性和荧光性能于一体的多功能纳米复合材料在生物技术和纳米药物方面具有潜在的应用。在本文中，我们以磁性Fe3O4为核，掺杂稀土的Y2O3荧光粉作为壳，主要以SiO2作为耦合剂，通过溶剂热法和共沉淀法制备一系列的磁性荧光双功能复合物。简单解释了这种双功能复合物在磁场下作用不同时间对荧光性质的影响。尝试以C和TiO2为耦合剂，探讨耦合剂对磁性荧光性能的影响。我们也讨论了单激活剂Eu3+和双激活剂Eu3+,Tb3+对双功能的影响，并给出了Tb3+离子的能量传递给Eu3+离子可能的机理。为了拓宽这种双功能复合物的应用，我们还通过采用牺牲模板的方法制备了中空介孔结构的磁性荧光纳米复合物，这种复合物有大的比表面积，良好的磁性和荧光性质。具体工作如下：
通过溶剂热法合成多功能的Fe3O4@SiO2@Y2O3:Eu3+纳米复合材料具有良好的核壳结构，各种表征技术证明了Fe3O4@SiO2@Y2O3:Eu3+纳米复合材料的磁性和荧光性能比Fe3O4@Y2O3:Eu3+好。核心表面的二氧化硅包覆层是三明治结构材料的基础，对改善磁性和荧光性质起到重要作用。样品在磁场下放置不同时间后，发光强度随时间的增加而增强，3小时后逐渐下降。复合物具有可调的光学性能，好的磁响应能力和稳定性。
我们成功合成了结合磁性和发光性能的Fe3O4@SiO2/C/TiO2@Y2O3:Eu3+纳米复合材料。Y2O3:Eu3+荧光粉可以很容易在偶联剂涂层后的四氧化三铁微球表面生长。对比三种不同耦合剂的纳米复合材料,活性炭层因为有键的作用，易于组合两种不同结晶结构的材料,综合磁性和荧光性能Fe3O4@C@Y2O3:Eu3+比其他两种复合物好些。而Fe3O4@SiO2@Y2O3:Eu3+的生物相容性更好些。不同耦合剂的复合物都具有好的磁响应性,独特的发光特性和乙醇溶解性高的优点。
碳作为牺牲模板，二氧化硅作为偶联剂，CTAB为结构导向剂，我们通过一个多步法合成了多功能的Fe3O4@HM-SiO2@Y2O3:Eu3+纳米复合材料。该材料显示了典型的有序中孔的特征，并且具有单分散的球形形态,光滑的表面和狭窄的粒度分布。此外，多功能纳米复合材料显示Eu3+的5D0-7F1-4的特征发射。磁性测量表明样品的顺磁特性。我们还比较了实心的Fe3O4@SiO2@Y2O3:Eu3+和中空介孔Fe3O4@HM-SiO2@Y2O3:Eu3+的磁性和荧光性能。
良好分散的Fe3O4@SiO2@Y2O3:Eu3+,Tb3+核壳结构纳米复合材料由简单的两步共沉淀方法合成。X射线衍射图谱表明，四氧化三铁核心具有良好的面心立方结构，SiO2层是无定形的，Y2O3层为立方晶系。纳米复合材料紫外线照射后，荧光光谱显示，在610nm处强烈的发射峰对应Eu3+的电偶极5D0-7F2跃迁，并在545nm处对应铽的5D4-7F5跃迁。我们从激发光谱中推测，存在从Tb3+到Eu3+离子的能量传递过程。
Nanocomposites have been playing important roles in modern science andtechnology.Dual-functional nanocomposites combined with magnetism andluminescence have potential applications in bio-and nano-technology drugs.In thisarticle, we synthesis a series of magnetic fluorescent compound through chemicalcoprecipition, where Fe3O4, Y2O3doped with rare-earth and SiO2were fabricated asmagnetic cores, shells and coupling agents.We tried to explain the influence ofdifferent interacting time to the fluorescence in the magnetic field. The couplingagents of carbon and TiO2were investigated effects to the magnetism andfluorescence. We also discussed the roles of Eu3+as single activator, Eu3+and Tb3+dual-activators to dual-functional applications, showing the possible mechanism ofenergy transferred from Tb3+to Eu3+ions. We speculate from excitation spectrum thatthere exists energy transfer from Tb3+to Eu3+ions.In order to broaden the applicationsof these bifunctional compounds, we also prepared hollow mesoporous compounds,which had large specific surface area, good magnetic and fluorescent properties viasacrificing template. Details were as follows:
In summary, we demonstrated a solvothermal synthesis of multifunctionalFe3O4@SiO2@Y2O3:Eu3+nanocomposites with well-defined core-shell nanostructures,magnetic and luminescent properties, which had superior performances thanFe3O4@Y2O3:Eu3+nanocomposites in magnetism and fluorescence by variouscharacterizationtechniques. The SiO2on the surface of magnetic core was the base tothe sandwich-structured materials, which was important to good magnetic andluminescent properties. The luminescence gradually increased in3h when the sampleswere in magnetic field for different time, then decreased，indicating tunable opticalproperties, good magnetic respondence and chemical stability.
We demonstrated a successful synthesis ofmultifunctional Fe3O4@SiO2/C/TiO2@Y2O3:Eu3+nanocomposites with the magnetic and luminescence properties in a core/shell frame. The Y2O3:Eu3+could easily grow on the coupling agents‘layercoating the Fe3O4microsphere.Compared with three different coupling agentnanocomposites, it was obvious that the chemical bonds in activated carbon layerpromoted to combine these two different crystalline structures, which made theFe3O4@C@Y2O3:Eu3+nanocomposites,had better proformance than Fe3O4@SiO2@Y2O3:Eu3+and Fe3O4@TiO2@Y2O3:Eu3+nanocomposites in magnetic andluminescent properties by various characterization techniques. However, differentcoupling agents all shown good magnetic respondence, unique luminescence and highsolubility in ethanol.
By usingcarbon as a sacrificial template, silica as coupling agent and CTAB asstructure-directingagent, we synthesized multifunctional Fe3O4@HM-SiO2@Y2O3:Eu3+nanocomposites via a multi-step. The results revealed that materials showtypical ordered mesoporous characteristics, havemonodisperse spherical morphologywith smooth surface and narrow size distribution. The multifunctionalnanocomposites show the characteristic emission of Eu3+（5D0-7F1-4）. Magnetismmeasurement revealed the paramagnetic feature of the samples. Besides we alsocompared the magnetic and fluorescent properties of solid Fe3O4@SiO2@Y2O3:Eu3+and Fe3O4@HM-SiO2@Y2O3:Eu3+.
The nanocomposites with good dispersion and core–shellstructures weresynthesized via a facile two-step co-precipitation process in the fabrication ofFe3O4@SiO2@Y2O3:Eu3+,Tb3+. XRD spectra showed that Fe3O4core has crystallizedin a good face-centered cubic structure; SiO2layer is amorphous and Y2O3layer iscubic. Nanocomposites excitated by UV irradiation, Fluorescence spectroscopyshown that there is a strong emission at around610nm corresponding to the forcedelectric dipole5D0–7F2transition of Eu3+and at around545nm corresponding to5D4-7F5transition of Tb3+. We speculated from excitation spectrum that there existedenergy transfer from Tb3+to Eu3+ions.
引文
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