【作者】 伍水生；

【导师】 尹双凤；

【作者基本信息】 湖南大学 ， 化学工程与技术， 2011， 博士

【摘要】 纳米材料研究是目前材料科学研究的一个热点,其相应发展起来的纳米技术被公认为是21世纪最具有前途的科研领域。目前合成纳米材料的方法虽然很多,但是获得尺寸可控、颗粒均匀的纳米材料仍然存在一定的困难。探索发展纳米材料设计与合成的新途径、新方法,实现对纳米材料的尺寸大小、粒径分布以及形貌和表面修饰的可控合成及其物理化学性质研究仍然是纳米材料研究领域的一个重要课题。本论文采用不同合成方法成功合成了几种具有可控形貌的纳米结构材料。通过调节反应物的浓度、反应时间、反应温度以及反应物比例等实验参数,获得了氧化物（SnO₂）、两种碳酸盐（BaCO₃、SrCO₃）和铁酸镍石墨烯复合物等纳米材料,并分别研究了他们的相关性质。利用X射线衍射（XRD）、红外光谱（FT-IR）、拉曼光谱（Raman）、扫描电镜（SEM）、透射电镜（TEM）/高分辨透射显微镜（HRTEM）、X射线光电子能谱（XPS）以及紫外-可见吸收光谱（UV-Vis）等多种分析测试手段对合成材料的形貌、结构、组份和性质进行了表征分析,主要研究内容和创新性成果包括以下几个部分:1、以生物分子L-赖氨酸作为碱源和螯合剂,通过水热合成方法制备了系列二氧化锡（SnO₂）纳米晶,以罗丹明B紫外光降解反应作为模型反应考察了SnO₂的光催化性能。研究结果表明,采用这种方法所得到的SnO₂纳米晶的平均粒径低于10 nm,而且制得了迄今为止晶粒最小且小于激子波尔半径（2.7 nm）的SnO₂纳米晶（2 nm）;生物分子的浓度、SnCl4/L-赖氨酸的摩尔比、水热反应温度和反应时间对SnO₂纳米晶的形状和颗粒大小影响不大。讨论了SnO₂纳米晶的水热合成温度和罗丹明B水溶液的pH值对紫外光催化降解罗丹明B反应活性的影响。研究结果表明180℃水热合成的纳米晶SnO₂,在碱性条件下的（pH=8）光催化性能最好,在150 min内光催化罗丹明B降解率接近100%。2、采用生物分子葡聚糖作为结构引导剂,通过模拟生物矿化的合成方法,在水溶液中实现了高度有序的BaCO₃的可控晶化和自组装。通过调节实验参数（例如葡聚糖浓度、Ba2+浓度以及反应时间）得到了由棒状微晶组成的树突状、哑铃状、球状等形貌的碳酸钡复杂纳米结构。所得产物的物相、形貌和微结构分别通过XRD、SEM、TEM、HRTEM和FT-IR进行分析表征。研究结果表明,树突状、哑铃状、球状复杂纳米结构的形成可能遵循棒-哑铃-球（R-D-S）的自组装生长机理。也探讨了碳酸钡复杂纳米结构改性后的超疏水性质。利用氟硅烷对碳酸钡复杂纳米结构表面处理,表面处理后的水接触角（CA）从亲水的52.9o变为疏水的156.3o。这表明物理结构和化学修饰可改变亲水性的表面为超疏水的表面。3、在N, N-二甲基甲酰胺（DMF）-水混合溶剂体系中,使用葡聚糖分子作为晶体修饰剂,矿化合成了具有不同形貌的碳酸锶纳米复杂结构,包括棒状、树突状、哑铃状以及球状分级复杂结构。探讨了一系列实验条件（如DMF与水的体积比、葡聚糖浓度、锶离子浓度以及反应时间）对碳酸锶纳米复杂结构形貌的影响。碳酸锶纳米复杂结构的生长可能遵循棒-哑铃-球（R-D-S）的自组装生长机理。体系中形成的氢键是该自组装生长方式的驱动力,对形貌有重要的影响。增大DMF与水的体积比或葡聚糖浓度可能会使体系氢键增多,从而有利于碳酸锶复杂纳米结构的形成。所合成的碳酸锶复杂纳米结构表面经氟硅烷处理后呈现超疏水性,另外该复杂纳米结构材料对染料分子也有较好的吸附性能。4、通过改进的Hummer法合成氧化石墨,对氧化石墨进行超声剥离,得到氧化石墨烯片层结构。铁离子和镍离子通过静电作用吸附在氧化石墨烯表面,滴加氨水沉淀,水热处理,最后经硼氢化钠还原制备了NiFe₂O₄@graphene复合纳米材料。通过XRD、FT-IR、Raman、TEM、HRTEM和XPS等分析测试手段对所合成NiFe₂O₄@graphene复合纳米材料进行系统的分析表征。结果表明,所合成的复合材料包含铁酸镍纳米颗粒和石墨烯,10-15nm左右的铁酸镍纳米颗粒结晶完整,几乎单分散锚固在石墨烯片上。磁性研究表明NiFe₂O₄@graphene复合纳米材料饱和磁强度（Ms）可达46.2 emu·g^-1,矫顽力（Hc）为11.2 Oe,几乎没有剩磁效应（Mr= 0.583 emu g-1）属超顺磁性纳米材料。更多还原

【Abstract】 The synthesis and design of nanometerials is the most promising research area for nanoscience, and it is also the base of the application and future development of nanotechnology. Due to the unique properties, small size effect, surface effect and quantum size effect, etc, which are different from their bulk substances, nanomaterials have great potential applications in the fields such as catalysis, environmental protection, bio-medicine, etc. The size and shape of the inorganic micro-nanomaterials have great influence on their physical and chemical properties. Thus, the synthesis and properties characterization of inorganic nanomaterials with controllable size, distribution, morphologies and structures are very important for the basical and applied research of new nanomaterials. In this dissertation, several different synthesis methods have successfully developed for synthesizing nano-structured materials with controlled morphology. By adjusting the reactant concentration, reaction time, reaction temperature and reactant ratio, we synthesize oxide （SnO₂）, two carbonate （BaCO₃, SrCO₃） and NiFe₂O₄ nanocrystals@graphene composite with controllable morphology and size. The morphology, structure and components of the obtained products are characterized and analyzed by X-ray diffraction （XRD）, infrared spectroscopy （FT-IR）, Raman spectroscopy （Raman）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM） /high resolution transmission electron microscopy （HRTEM）, X-ray photoelectron spectroscopy （XPS）, UV-visible absorption spectroscopy （UV-Vis）, etc. The formation mechanisms of the as-synthesized nanostructures are discussed and their properties are also investigated. The main results and innovative achievements are summarized as follows:1. SnO₂ nanocrystals were prepared by using a biomolecule （L-lysine）-assisted hydrothermal method. The as-synthesized products were characterized by XRD, Raman, FT-IR and TEM/HRTEM. The reaction parameters, including the concentrations of biomolecule or the ratio of the SnCl4/L-lysine, reaction temperature and time, had little effect on the size and shape of the as-synthesized SnO₂ nanocrystals. This synthesis route led to almost monodisperse products with particle sizes below 10 nm. The L-lysine functioned as both a source of alkali and a chelating agent. The as-synthesized nanocrystalline SnO₂ had excellent phtotcatalytic degradation of RhB under UV irradiation which was attributed to the more oxygen vacancies on the surface of the nanocrytalline SnO₂. The photocatalytic activity of the SnO₂ nanocrystalline was optimized. Under the basic condition（pH=8）, SnO₂ nanocrystals synthesized at 180℃held the best catalytic property activit with the degradation of RhB, close to 100% within 150 min.2. Shape-controlled crystallization and self-assembly of high-ordered BaCO₃ architectures were synthesized by using dextran as the structure directing agents in aqueous solution. The phases, morphologies and structures of the products were characterized by XRD, SEM, TEM, HRTEM and FT-IR spectrophotometer. Dendrite-like, dumbbell-like, and spherical BaCO₃ complex nanostructures were obtained by tuning the experimental parameters such as the concentration of dextran, the concentration of Ba2+ cations and reaction time. The formation of dendrite-like, dumbbell-like, and spherical complex nanostructures could be explained by a rod-dumbbell-sphere （RDS） self-assembly growth mechanism. The surface properties of BaCO₃ crystals were successfully modified to be superhydrophobic using fluorosilane as modifier. The superhydrophobicity of BaCO₃ complex nanostructures was attributed to the combination of chemical composition and the textured topography. The superhydrophobic properties of as-resulted products may have potential applications as filler in composite materials.3. We reported the biomineralization in vitro of SrCO₃ complex nanostructures obtained by using glucosan as the modifier in the dimethyl formamide （DMF）-deionized water （DIW） mixed solvents. Rod-, dendrite-, dumbbell-, and sphere-like SrCO₃ nanostructures were achieved by tuning the volume ratio of DMF/DIW, reaction time, and concentrations. The phase, structure, and morphology of the as-obtained products were characterized by XRD, SEM, TEM, HRTEM, FT-IR spectroscopy, and Bunauer-Emmett-Teller （BET） analysis. The possible formation mechanism of SrCO₃ complex nanostructures follows the rod-dumbbell-sphere growth process. Both higher DMF/DIW ratios （i.e., more DMF molecules） and larger glucosan concentrations in the mineralization process were in favor of the self-assembly process, due to more hydrogen bonds may formed in the system,which led to the formation of dumbbells and spheres. The as-synthesized SrCO₃ complex nanostructures had excellent adsorption properties and superhydrophobicity, which may open up a wide range of potential applications in environmental protection.4. NiFe₂O₄ nanocrystals@graphene composite （NFGC） was synthesized via a simple chemical deposition method by using graphene oxide as a precursor. The as-synthesized product was systematically characterized by XRD, FT-IR, Raman,TEM, HRTEM, XPS, respectively. The magnetic property of the NiFe₂O₄ nanocrystals@graphene composite was also investigated. The results shown that the NiFe₂O₄ nanocrystals homogeneously anchored to the graphene sheets were well-crystallized particles, with an average size of 10-15 nm. Magnetic measurement reveals the NiFe₂O₄ nanocrystals@graphene composite was superparamagnetic with a saturation magnetization of 46.2 emu·g^-1, a coercivity of 11.2 Oe and remanence effect of 0.583 emu·g^-1.更多还原