【作者】 邓字巍；

【导师】 武利民；

【作者基本信息】 复旦大学 ， 材料物理与化学， 2008， 博士

【摘要】 近年来，各种特殊结构形貌纳米材料的制备及其性能研究，引起人们极大兴趣，其中以空心微球和含金属纳米粒子介电复合微球的研究备受关注。空心微球作为一种新型功能材料，具有较大的比表面积，较小的密度，表面可渗透性，中空部分可容纳客体分子等优点；含金属纳米粒子介电复合微球，其金属纳米粒子自身的表面等离子体共振，以及它引起金属纳米粒子内部和周围附近局域电磁场增强等特性，赋予了复合微球材料很好的光、电、磁等性能。因此，对这些功能微球材料制备和应用的研究，有着深远的理论意义和应用前景。本论文分别在相同介质条件下通过“一步法”制备了单分散SiO₂、ZnO空心微球，整个制备过程无需溶剂溶解或高温煅烧等后处理模板步骤，形成空心微球方法操作简单；利用聚乙烯吡咯烷酮（PVP）还原与稳定双重作用，将贵金属Ag纳米粒子有效的复合到SiO₂微球表面，整个制备过程无需添加其它还原剂还原银盐以及对SiO₂表面进行修饰处理。而且，对这些功能微球材料所具有的光催化性能，催化性能以及表面增强拉曼光谱（SERS）性质分别做了研究，具体研究内容及结果如下：（1）基于本实验组独创制备微米级大粒径空心微球的基础上，进一步制备出小粒径单分散SiO₂空心微球。通过偶氮二异丁基脒盐酸盐（AIBA）为阳离子引发剂，聚乙烯吡咯烷酮（PVP）为稳定剂，采用无皂乳液聚合制备出小粒径聚苯乙烯（PS）微球分散液。经透析处理后，加入EtOH控制PS分散液固含量。在此PS分散液中加入氨水和正硅酸乙酯（TEOS），通过TEOS的水解-缩合反应形成SiO₂纳米粒子。由于PS微球表面带正电荷基团，而SiO₂粒子表面的羟基呈负电荷，因此可以通过静电相互作用将SiO₂吸附到PS微球表面，形成SiO₂包覆PS的复合微球。同时，由于催化剂氨水的加入，碱性的乙醇介质能够“溶解”刻蚀PS模板微球，形成空心SiO₂微球，从而实现了小粒径SiO₂空心微球在相同介质条件下的“一步法”制备，且空心微球形态以及壳层厚度可通过氨水，TEOS浓度进行调节控制。整个制备过程相对简单，不需要采用传统无机空心微球制备时所需的溶剂溶解、高温煅烧等后处理模板微球过程。（2）在上述“一步法”制备空心微球研究的基础之上，通过控制实验条件在相同介质下进一步制备出ZnO空心微球，并研究ZnO空心微球的光催化活性。采用分散聚合制备出单分散PS微球，并在浓H₂SO₄中发生磺化反应，形成表面带有磺酸基团壳层的PS微球。选用磺化PS微球为模板，分散于乙醇介质中，分别加入Zn（Ac）₂·2H₂O，NaOH乙醇溶液。当带正电荷的锌离子通过静电作用被完全吸附到磺化PS微球表面后，并与加入的NaOH，在60℃条件下反应形成ZnO纳米晶。这些新生成的ZnO纳米晶继续进行粒径增长，并逐渐在PS微球表面形成ZnO壳层。当在此过程中或过程后，磺化的PS微球被碱化的乙醇介质所“溶解”刻蚀，形成ZnO空心微球。与其它制备ZnO空心微球方法相比，不需再外加有机溶剂或通过高温煅烧来除去模板微球；同时制备条件相对温和，不需要很高的反应温度和很长反应时间来获得空心结构。制备的ZnO空心微球表现出很好光催化性能，可作为光催化剂在紫外光照射下光催化降解有机染料溶液。（3）以St（?）ber方法制备的SiO₂微球为模板，通过SiO₂微球表面Si-OH的静电作用，将[Ag（NH₃）₂]⁺吸附到微球表面，利用聚乙烯吡咯烷酮（PVP）稳定和还原的双重作用，将[Ag（NH₃）₂]⁺成功地还原成Ag纳米粒子，制备出稳定的SiO₂／Ag复合微球。与其它制备含银纳米粒子的复合微球方法相比，整个过程中无需再添加其它还原剂还原银盐以及对SiO₂表面进行修饰处理。且SiO₂微球表面的银纳米粒子大小和银粒子覆盖程度，可以通过[Ag（NH₃）₂]⁺浓度控制。利用透射电镜（TEM）、扫描电镜（SEM）、X-射线光电子能谱（XPS），X-射线衍射仪（XRD）和紫外-可见分光光度计对形成的SiO₂／Ag复合微球进行了表征。同时研究表明制备出的SiO₂／Ag复合微球可以用于催化剂催化还原有机染料溶液，表现出很好的催化活性。SiO₂／Ag复合微球作为活性基底材料，使检测的对巯基苯胺拉曼光谱信号明显增强，表明SiO₂／Ag复合微球表现出表面增强拉曼光谱（SERS）特性。更多还原

【Abstract】 In recent years, the strategy to fabricate nanomaterials with particular structures and morphologies like hollow spheres and core-shell composite spheres with metallic nanoshells is of burgeoning interest. Hollow spheres as new advanced functional materials are becoming one focused research field, principally because of their novel properties, such as low density, high specific surface areas and infiltration ability. Composite spheres with metallic nanoshells can display novel and enhanced properties （e.g. mechanical, chemical, electrical, rheological, magnetic and optical and so on）,which is due to plasmon resonances excitation from metal nanoparticles and their enhancement of the electromagnetic field around metal naoparticles.In this study, inorganic hollow spheres SiO₂, ZnO were prepared via a facile method in the same media respectively, and SiO₂/Ag composite spheres were prepared by the aid of reducing and stabilizing function of polyvinylpyrrolidone （PVP）. In addition, the photocatalytic, catalytic and surface-enhanced Raman scattering （SERS） performances of these spheres were investigated respectively. All the research contents and results are shown as follows:（1） In the first chapter, based on the method of preparation of the micro-size hollow spheres reported by our group, monodisperse hollow silica spheres with small sizes were further prepared via one-step method using around 260nm PS as template particles, which were synthesized via emulsifier-free emulsion polymerization usingα,α’-azodiisobutyramidine dihydrochloride （AIBA） as a initiator and polyvinylpyrrolidone （PVP） as a stabilizer. In this approach, the obtained polystyrene suspension was dialyzed in ethanol using cellulose membrane and the solid content of polystyrene suspension was tailored through the addition of ethanol. Then hydrolysis and condensation of TEOS was carried out in aqueous ammoniacal alcohol medium at 50℃, in which PS particles were "dissolved" subsequently even synchronously in the same medium to form hollow silica spheres. And the morphology and thickness of hollow silica spheres could be adjusted through the concentration of ammonia and TEOS in the formulation respectively. Neither additional dissolution nor calcination process was needed to remove the polystyrene cores.（2） In the second chapter, ZnO hollow spheres were further prepared via a facile method. Monodisperse PS spheres were first prepared by dispersion polymerization and then sulfonated by concentrated sulfuric acid. The formed sulfonated polystyrene core-shell spheres were used as template spheres, when Zn（Ac）₂·2H₂O was added into the ethanol dispersion of the template spheres, zinc ions were first adsorbed onto the surfaces of template spheres via electrostatic interaction. The NaOH solution was added into the mixture and reacted with zinc ions to form ZnO crystal nucleus which was followed by the growth step to form ZnO nanoshells.During the formation of ZnO nanoshells or later on, the sulfonated polystyrene core-shell spheres were "dissolved" in the same media to obtain ZnO hollow spheres directly. Neither additional dissolution nor calcination process was needed to remove the template cores, and reaction condition was mild, neither high temperature nor long time was needed. TEM, SEM, XPS and XRD were used to investigate the morphology, surface composition and crystalline structure of the ZnO hollow spheres, respectively. UV-visible spectra show these ZnO hollow spheres had very good photocatalytic activity.（3） In the last chapter, we described a novel method for fabrication of SiO₂/Ag composite spheres by the aid of reducing and stabilizing function of polyvinylpyrrolidone （PVP）. In this approach, [Ag（NH₃）₂]⁺ ions were first adsorbed onto the surfaces of silica spheres via electrostatic attraction between the silanol groups and ions, these [Ag（NH₃）₂]⁺ ions adsorbed on silica spheres were then reduced and protected by PVP to obtain SiO₂/Ag composite spheres. Neither additional reducing agent nor the core surface modification was needed, the particle size and the coverage degree of silver nanoparticles on the silica spheres could be easily tuned through altering the concentration of the precursor-[Ag（NH₃）₂]⁺ ions. UV-visible spectrometer analysis showed these composite spheres had very good catalytic property; Raman spectrometer measurement displayed that these composite spheres occupied excellent surface-enhanced Raman scattering （SERS） performance.更多还原