【作者】 刘德明；

【导师】 杨桦；

【作者基本信息】 吉林大学 ， 物理化学， 2012， 博士

【摘要】 近年来磁性荧光纳米粒子因为在生物荧光成像，药物投递，和治疗方面的潜在应用，受到了越来越多科学工作者的关注。然而自然界中并没有一种材料同时具有荧光和磁性，因此需要将两种性质结合到一种纳米复合物中。可给科学工作者选择的磁性材料主要包括：四氧化三铁，γ-三氧化二铁，磁性金属粒子。主要的制备方法有共沉淀法，热分解法，微乳胶法和水热、溶剂热合成法。这些方法都有自己的特点，制备的磁性纳米粒子粒径和分散性也各有不同。四氧化三铁因为制备方法简单，成本较低，磁性强而被广泛用于合成双功能纳米复合物。荧光材料可选的种类较多，主要分为无机和有机两大类。无机荧光材料包括镧系稀土离子掺杂化合物，半导体量子点；有机荧光材料包括有机染料，荧光蛋白。包覆的方案主要有磁性材料作为核，外层包覆荧光材料，或者两种材料混合被另一种包覆。然而每种路线的选择和材料的应用都有各自的优缺点，有很多挑战摆在科学工作者的面前。例如，铁氧化物具有光催化性，有机发光材料与之相接处在光照下会被分解。而无机发光材料中ZnS可以溶于四氧化三铁，形成锌铁氧体固溶体，失去发光性和磁性，这种问题可以通过中间加入隔离层解决。镧系稀土掺杂化合物的制备需要高温处理，如果用它作为荧光材料包覆在磁性材料外层，那么高温会破坏磁性材料，导致复合物的磁性能降低，这同样是很棘手的问题。本文的主要目的是合成具有磁性和发光性能的双功能纳米复合物，并通过各种测试手段，如X射线衍射（XRD），透射电子显微镜（TEM），场发射扫描电子显微镜（FESEM），来确定产物的结构，用荧光光谱（PL），振动样品磁强计（VSM）对产物的荧光性质和磁性质进行研究。主要工作内容如下：1.我们选取镧系稀土离子掺杂化合物作为荧光材料，水热法制备的四氧化三铁作为磁性材料，采用荧光物质作为核，外层包覆四氧化三铁的设计思路合成双功能纳米复合物。这种磁性在外，发光在内的包覆形式可以避免制备荧光纳米粒子时的高温处理步骤破坏四氧化三铁结构，导致双功能纳米复合物磁性过低的现象出现。我们用溶胶凝胶法制备分别掺杂铕离子的钒酸钇前驱体，在经过高温煅烧之后得到YVO₄：Eu³⁺纳米粒子，用这种荧光纳米粒子作为核，通过水热法合成四氧化三铁包覆在外层，制得同时具有磁性和荧光性能的纳米复合物。我们通过XRD确定了合成的双功能纳米复合物中同时存在Fe₃O₄和YVO₄：Eu³⁺相，用TEM确定双功能纳米复合物具有核壳结构，用FESEM表征了包覆前后的形貌变化。重点用PL对复合物和单纯荧光材料的荧光光谱进行了研究，讨论Fe₃O₄对YVO₄：Eu³⁺荧光性质的影响。同时也通过VSM对复合物的磁性能进行了表征。我们还讨论了在包覆四氧化三铁层时不同表面活性剂和溶剂对YVO₄：Eu³⁺_5%@Fe₃O₄双功能纳米复合物形貌和发光性能的影响。2.在上一章的基础上我们合成并研究了YVO₄：Dy³⁺@Fe₃O₄荧光磁性纳米复合物，对比单纯的YVO₄：Dy³⁺荧光纳米粒子研究了Fe₃O₄对荧光性质的影响，并得到Dy最佳掺杂浓度为1%，同时研究了YVO₄：Dy³⁺@Fe₃O₄与Fe₃O₄的磁性质。3.我们用溶胶凝胶法制备了YVO₄共掺杂不同化学计量比的Eu³⁺和Dy³⁺前驱体，经过高温煅烧制备了能够发射不同颜色荧光的YVO₄：Eu³⁺_x%，Dy³⁺_y%纳米粒子，用CTAB分散在水溶液中，通过水热法包覆一层四氧化三铁壳，从而制备了能够在同一波长激发光下发射不同荧光在双功能纳米复合物。我们用XRD，TEM对双功能纳米复合物的结构形貌进行了表征，用PL对双功能纳米复合物的荧光性质进行了研究，同时也研究了四氧化三铁对荧光材料的发光影响，得到各个发射峰位的变化曲线图，我们可以通过这组曲线来设计希望得到的发光颜色双功能纳米复合物。用VSM对双功能纳米复合物的磁性能进行了表征。最终我们得到了具有橘黄色，橙红色，逐渐趋于红色荧光发射的双功能纳米复合物，加上上两章中的单独的稀土离子掺杂纳米复合物，我们就可以合成在相同激发波长下能够发射黄绿光，橘黄光，橙红光，红光等不同颜色的双功能纳米复合物。4.在第五章中介绍了我们合成Fe₃O₄/ZnS荧光磁性双功能复合物的实验过程及对复合物荧光性质和磁性的研究结果。我们用水热法钴作为催化剂逆向歧化反应二价铁合成Co_xFe_1-x/CoFe_3-yO₄复合物，我们研究了钴的掺杂量对产物结构的影响，得知钴的掺杂量不能超过Co：Fe=1，超出则出现杂相。我们用这种磁性复合物作为磁性核，外层修饰了ZnS作为发光材料，得到具有荧光磁性的复合物。因为磁性核中含有磁性金属单质，所以具有较高的磁性能，但是ZnS受到磁核的影响，发光性能较低。因此我们为了提高ZnS的发光强度，掺杂不同浓度的Mn²⁺来提高发光性能，确定较好的掺杂量为_5%摩尔分数。然后为了降低复合物的粒径，我们用水热法制备的Fe₃O₄纳米粒子代替Co_xFe_1-x/CoFe_3-yO₄复合物，同时因为ZnS可以溶解在Fe₃O₄中，我们在包覆ZnS之前在Fe₃O₄外层包覆了一层约16nm的SiO₂层，用来隔离发光物质和磁性物质。这样就得到了直径在550nm⁹00nm之间的Fe₃O₄@SiO₂@ZnS：Mn_5%纳米复合物，具有最强发射峰在490nm处的荧光发射，和饱和磁化强度27.6emu/g的磁性能。更多还原

【Abstract】 In recent years, bifunctional nanocomposites that exhibit significant magneticmoment and luminescence have attracted much attention because of many potentialapplications in biological fluorescence imaging, drug delivery, and treatment. Innature, materials that exhibit significant magnetic moment and luminescence do notexist. The magnetic material can be used for nanocomposites, including: iron oxide,γ-ferric oxide, magnetic metal particles. The main preparation methods arecoprecipitation, thermal decomposition method, micro-emulsion method andhydrothermal, solvothermal synthesis method. These methods have its owncharacteristics. The preparation of magnetic nano-particle size and dispersion are alsodifferent. The iron oxide is widely used, for the simple preparation method, low cost,strong magnetic. The fluorescent materials include inorganic and organic twocategories. Inorganic fluorescent materials include the lanthanide rare earth ion-dopedcompounds, semiconductor quantum dots; organic fluorescent materials, includeorganic dyes, fluorescent proteins. The design of the composites is used magneticmaterial as the core, the outer layer coated with a fluorescent material, or a mixture oftwo material is coated by another. However, each route selection and application ofthe material have its own advantages and disadvantages, there are many challengesplaced in front of scientists. As the iron oxide particles are photocatalysts, thisnanocomposite must be stored away from daylight. The inorganic light-emittingmaterial ZnS can dissolve in the iron oxide to form zinc ferrite solid solution. Theywill lose the luminescence and magnetic. The problem can be solved by the middlebarrier. Preparation of lanthanide rare-earth doped compounds need high-temperatureprocessing. If it is used as the fluorescent material coated on the magnetic materials,the magnetic material will be destroyed. In this paper, we would like to synthesize a series of bifunctionalnanocomposites with magnetic and luminescent properties. The structure,luminescent and magnetic properties of the nanocomposites were investigated byX-ray diffraction （XRD）, transmission electron microscopy （TEM）, field emissionscanning electron microscope （FESEM）, fluorescence spectroscopy （PL）, andvibrating sample magnetometer （VSM）. The main contents are as follows:1. We select the lanthanide rare-earth ions doped compounds as fluorescentmaterials, iron oxide synthesized by a hydrothermal method as magnetic materials.We use fluorescent nanoparticles as the core coated with iron oxide to synthesizebifunctional nanocomposites. This strategy, the phosphor coated with iron oxide,could avoid the high-temperature process of the preparation of phosphors, which candestroy the magnetic materials. We used the Sol-gel method to produce the yttriumvanadate doped with europium ion precursor. After high-temperature calcination, weobtained the YVO₄: Eu³⁺nanoparticles. We used them as the nucleus, coated withFe₃O₄which synthesized by the hydrothermal method, then obtained magneto-opticbifunctional nanocomposites. We investigated the bifunctional nanocomposites byXRD, TEM, FESEM to determine their component, struction, and morphology. Wefocused on the luminescent properties of the nanocomposites and the phosphors, andinvestigated by PL. We discussed the impact of iron oxide on the luminescence. Themagnetic properties of the nanocomposites and the iron oxide were investigated byVSM. We also discussed the impact of the different surfactants and solvents, whichused to disperse the phosphors in the synthesis of Fe₃O₄, on the morphology and theluminescent properties of the YVO₄:Eu³⁺_5%@Fe₃O₄bifunctional nanocomposites.2. Based on the previous chapter, we synthesized the YVO₄:Dy³⁺@Fe₃O₄magneto-optic nanocomposites, and studied their luminescent and magneticproperties. We studied the impact of Fe₃O₄on the luminescent properties ofnanocomposites contrast to the pure YVO₄: Dy³⁺nanoparticles. The optimal dopingconcentration of Dy is1%. We also studied the magnetic properties of theYVO₄:Dy³⁺@Fe₃O₄nanocomposites and the pure Fe₃O₄nanoparticles.3. We were successfully prepared a series of different concentrations of Eu³⁺,Dy³⁺codoping YVO₄@Fe₃O₄magnetic phosphors by using two steps route, including Sol-gel and hydrothermal method. We calcined the precursors whichprepared by the Sol-gel method to get the phosphors, then used CTAB to dispersethe phosphors in aqueous solution for coated with the Fe₃O₄which prepared by thehydrothermal method. Finally, we got a series of bifunctional nanocomposites withdifferent optical emission peaks, which excited in the same wavelengths. Wecharacterized the structure of the bifunctional nanocomposites by XRD, TEM. Weused PL to study the luminescent properties of nanocomposites. We also studied theimpact of Fe₃O₄on the luminescent properties of the phosphors, and got plots ofemission peaks intensity variation with various co-doping concentrations. We candesign nanocomposites with the desired emission. We characterized the magneticproperties of the nanocomposites by VSM. Finally, we successfully synthesized aseries of bifunctional nanocomposites with orange emission and orange-redemission. As increasing the co-doping concentration, the color gradually turned tored. Adding the rare-earth single-doped nanocomposites prepared in the previouschapters, we got the bifunctional nanocomposites with different emissions, such asyellow-green, orange, orange-red, red, in the same excitation wavelength.4. In the fifth chapter, we introduced the synthesis process of Fe₃O₄/ZnSmagneto-optic bifunctional composites and the findings of the fluorescent andmagnetic properties of the composites. We synthesized the Co_xFe_1-x/CoFe_3-yO₄composites by using cobalt as a catalyst to disproportion Fe （II） under hydrothermalcondition. We studied the influence of cobalt doping on the structure of thecomposites, and learned that cobalt doping amount can not exceed the Co: Fe=1. Ifit was excess, the hybrid phase would appear. We used these magnetic composites asthe magnetic core, modified with ZnS as luminescent materials, to synthesizebifunctional composites. Because of the magnetic metal in the core, the Ms of thebifunctional composites was high. However the fluorescent intensity of the ZnS wasdecreased affected by the magnetic core. In order to improve the fluorescentintensity of ZnS, we doped with different concentrations of Mn²⁺as an excitationcentre. The optimum is5mol%. We used the Fe₃O₄nanoparticles prepared by thehydrothermal method instead of Co_xFe_1-x/CoFe_3-yO₄composites, in order to reducethe particle size. Because ZnS can be dissolved in Fe₃O₄, we used16nm SiO₂as a barrier to isolate the luminescent material and magnetic material. We got Fe₃O₄@SiO₂@ZnS: Mn_5%nanocomposites with the diameter between550nm⁹00nm, theemission peak at490nm, and the saturation magnetization27.6emu/g.更多还原