【作者】 沈晔茜；

【导师】 丁维平； 郭学锋；

【作者基本信息】 南京大学 ， 物理化学， 2011， 博士

【摘要】 作为一个典型的过渡态金属元素,钒元素可以形成多种不同类型的一元氧化物或多元氧化物(钒酸盐)。一元氧化物和钒酸盐由于其结构的独特性而具有一些特殊的性能。本论文采用水热合成法制备了几种钒的一元氧化物和二元氧化物的纳米晶、纳米管结构,通过控制条件,在一定范围内实现了对产物形貌的有效控制。利用粉末X射线衍射(XRD)、透射电子显微镜(TEM)、扫描电子显微镜(SEM)、傅里叶变换红外光谱(FT-IR)、X寸线光电子能谱(XPS)、共聚焦显微拉曼光谱(Raman)等手段对产物的形貌、结构和成分进行分析,并结合光致发光光谱(PL)、紫外可见吸收光谱(UV-Vis)等表征手段,研究了材料在光致发光和光催化等方面的性能。主要内容包括以下几个部分：1、掺杂Ca2+的CeVO4纳米晶结构的制备与性能研究采用一种简单的水热合成方法,在不添加任何表面活性剂或模板剂的前提下,仅通过调节体系pH值即可有效控制合成不同形貌的CeVO4纳米晶结构,为了研究+2价离子掺杂对CeVO4纳米晶催化性质的影响,用类似的方法合成了CeVO4:Ca2+纳米晶。样品采用TEM, HRTEM, XRD和ICP, XPS,51VNMR、TPR等手段对其形貌、结构和氧化还原性质进行表征,并通过对掺杂前后纳米晶的Raman表征结合理论计算结果,分析其特殊的局部微环境,详细研究了掺杂对CeVO4结构的影响,揭示了掺杂离子改变纳米晶材料性质的本质,同时考察了该纳米晶材料在光催化降解亚甲基蓝反应中的催化性能。2、Eu3+掺杂LaVO4纳米材料的制备与发光性能研究采用水热合成方法制备了LaVO4纳米晶,并对合成条件进行细化分析,确定了决定其形貌、结构的主要因素,通过调变实验条件得到形貌可控的纳米棒和纳米颗粒,且成功的将Eu3+掺杂入晶格。通过测量样品的发光性质,考察了不同形貌、不同晶系、不同掺杂量对LaVO4:Eu3+样品荧光光谱的影响,并初步讨论了纳米材料量子效率偏低的原因所在,同时考察了表面处理对样品发光性质的影响。3、VOx-有机胺有机-无机复合纳米管制备及合成机理探讨开发了一种新型有效的制备钒氧化合物纳米管的方法：通过向体系中加入少量辅助模板剂TMAOH,并将超声应用于在前体处理中,从而极大的提高了有机胺模板剂向钒氧化合物无机层的插入反应速度,也有助于将钒氧化合物剥离为薄片,从而缩短了水热合成的时间,得到了形貌更为均一且管壁较薄的VOx-有机胺纳米管结构。其形貌和结构通过透射电子显微镜(TEM)、高分辨透射电子显微镜(HRTEM)、扫描电子显微镜(SEM)以及小角度X射线衍射(SASRD)、傅里叶变换红外光谱(FT-IR)、X射线光电子能谱(XPS)等实验技术手段来进行表征。并进一步考察纳米管的结构特点,采用改进的索氏萃取法成功的去除了VOx-有机胺纳米管中的有机物模板,从而第一次制备得到了不含有机模板剂的VOx纳米管结构。更多还原

【Abstract】 Vanadium oxide and vanadate nanomaterials with uniform size and shape are of special interest from both theoretical and practial perspectives because of their special structures and intrinsic properties. This thesis focuses on the morphology-controllable synthesis of the lanthanide vanadate nanocrystals and VOx nanotubes. The structures, morphologies, and composition are characterized by using multi spectroscopic techniques such as powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared absorption spectra (FT-IR), X-ray photoelectron spectroscopy (XPS) and Raman spectra, etc. In addition, the possible application of the prepared products in photo-catalysis, photo-luminesce are also studied. According to consecution and corresponding experimental results, this thesis is divided into three parts:1. Hydrothermal Synthesis, Characterization and Photocatalytic Activity of Doped CeVO4nanocrystalsSingle-crystalline CeVO4and CeVO4:Ca2+nanocrystals (NCs) were prepared via a hydrothermal method in the absence of any surfactant or template. TEM, HRTEM, XRD and ICP were used to characterize the morphology and structure of the products. The substitution of aliovalent cation Ca2+changed the stoichiometry in order to preserve the charge neutrality. XPS and solid state51V NMR spectra have confirmed that there is a valence change from Ce3+to Ce4+for a fraction of cerium atoms whereas the vanadium atoms remain in the pentavalent state V5+upon the substitution of Ca2+into CeV04. Raman spectroscopy is used to monitor the effects of the doping ion on CeVO4lattice contraction and distortion. The appearance of the shifted or broadened Raman peaks for the doped CeVO4is understood by theoretical calculations based on Vienna ab initio simulation package. The redox properties of these nanocrystals have also been investigated by TPR techniques, and the different photocatalytic activity on degradation of methylene blue is investigated.2. Synthesis and Photoluminescence properties of LaVO4:Eu3+nanocrystalsLaVCO4and Eu3+doped LaV04nanorod and nanocubic are synthesized by using hydrothermal method. The dimensions and morphologies of the products could be effectively controlled by adjusting experimental conditions. And the effects of different synthetic conditions on the morphologies, structures and photoluminescence properties of products are investigated. For Eu3+ions doped phosphors, the structure of the host and the lattice site of Eu3+ions are very important factors that affect emission efficiency, and the transformation from monazite to the zircon structure resulted in a remarkable improvement of the luminescent properties. Quantum efficiency of nanostructured LaVO4:Eu3+is also discussed.3. High efficient synthesis of VOx nanotubes by cooperation of tetramethylamine hydroxide and tetradecylamineA simple, rapid and highly effectient method for the synthesis of uniform vanadium oxide nanotubes with the cooperation of tetramethylammonium hydroxide (TMAOH) and tetradecylamine are successfully developed. The cooperation between TMA+and C14H29NH3+under ultrasound for the delamination of V2O5layered vanadium oxide is a more efficient procedure than the ones used before. Thin VOX nanosheet can be formed easily and the followed scrolling procedure under hydrothermal treatment requires a shorter period of time. Structure and morphology of the nanotubes are characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), small angle X-ray diffraction (SAXRD) and Fourier transform infrared (FT-IR). The surfactants are successfully removed during Soxhlet extraction for about10h, and the VOx nanotubes without surfactants are reported for the first time. This new approach to the synthesis of VOx nanotube opens up a range of possible applications in the preparation of nanocomposites with novel properties and morphologies.更多还原