纳米材料论文：亚磷酸氢镍、钒酸铜三维有序微-纳米材料的液相合成及性质研究

第一篇：纳米材料论文：亚磷酸氢镍、钒酸铜三维有序微-纳米材料的液相合成及性质研究

纳米材料论文：亚磷酸氢镍、钒酸铜三维有序微/纳米材料的液

相合成及性质研究

【中文摘要】三维(3D)有序微/纳米材料与体相材料相比有更优异的物理、化学性质,已被广泛应用于磁学、电化学、催化和光学领域。迄今为止,各种各样的合成方法已应用于三维有序微/纳米材料的制备。特别是液相法,因操作简单,产量高,耗能低而备受科学家及研究人员的关注。本论文以液相法为基础设计合成了亚磷酸氢镍、钒酸铜三维有序微/纳米材料。对所合成材料的组成、形貌及结构进行了详细的探究并对其磁性、电化学性质进行了初步的探究。主要研究内容为:(1)以乙二醇和水做溶剂,六偏磷酸钠做磷源,在没有任何表面活性剂条件下,以溶剂热法合成了具有三维花状的亚磷酸氢镍。性质测试结果表明该三维微/纳米材料表现出优异的磁学性质。研究发现反应时间和磷源对产物最终形貌有重要的影响。(2)运用表面活性剂(CTAB)辅助的水热方法,以偏钒酸氨,碱式碳酸铜为原料合成了三维花状结构的钒酸铜微/纳米材料并对其生长机理以及电学性质进行了研究。研究发现表面活性剂和反应时间对产物的最终形貌的形成起了很重要的作用。其电化学性质表明该形貌的钒酸铜具有较大的放电容量,可以作为可植入式心脏复律除颤器(ICD)一次电池的阳极材料。(3)以五氧化二钒为钒源,碱式碳酸铜为铜源,在没有任何表面活性剂条件下,以水为溶剂合成了以纳米棒为结构单元自组装形成的三维球状钒酸铜微球纳米材料。据我们所知,这是首次有报道的钒酸铜三维结

构微纳米材料。

【英文摘要】Three-dimensional organized nanomaterials have exhibited speical optical, electric, magnetic and catalytic properties and potential applications in various research and industrial fields, which are different from those of bulk phase.So far, various methods have been applied to fabricate 3D ordered nanostructures.Because of the virtues of simple conducting, high yields and low wasting, liquid methods have been welcomed by scientists.Therefore, our study were focused on NiHPO3·H2O, Cu3V2O7（OH）2·2H2O 3D ordered nanostructures based on liquid methods.We also studied the the composition, morphology and structures of the ordered structures.Magnetic and electrochemical properties also have been studied.（1）Self-assembled three-dimensional（3D）flowerlike NiHPO3·H2O micro/nanocomposite structure has been successfully synthesized for the first time by a simple solvothermal method, employing EG/ H2O as the solvent, Na6P6O18 as phosphor source without the assistance of any template or surfactant.Our study delivered that the magnetic property of the obtained NiHPO3·H2O have also been discussed.Some factors influencing the morphology of the NiHPO3·H2O flowerlike micro/nanocomposite structures were systematically

investigated.（2）Cu3V2O7（OH）2·2H2O microflowers were fabricated via a simple hydrothermal process in the presence of cetyltrimethylammonium bromide（CTAB）.Some factors influencing the morphology of the Cu3V2O7（OH）2·2H2O flower-like micro/nanocomposite structures were systematically investigated.The electrochemical measurements revealed that the Cu3V2O7（OH）2·2H2O microflowers displayed a high discharge capacity, which indicate that the 3D Cu3V2O7（OH）2·2H2O microstructures are promising cathode candidates for primary lithium batteries used in long term implantable cardioverter defibrillators（ICD）.（3）Uniform Cu3V2O7（OH）2·2H2O microspheres assembled by nanorods have been fabricated through simple hydrothermal method for the first time without the assistance of any template or surfactant.The Electrochemical measurements revealed that the Cu3V2O7（OH）2·2H2O microspheres displayed a high discharge capacity.【关键词】纳米材料 自组装 溶剂热法 磁学性质 电化学性质 【英文关键词】Nano Materials Self-Assembled Solvothermal Method Magnetic Properties Electrochemical Properties

【目录】亚磷酸氢镍、钒酸铜三维有序微/纳米材料的液相合成及性质研究8-168-10摘要4-51.1 引言

Abstract5

第一章 绪论

1.2 纳米材料的定义与特性

1.4 过渡金属磷酸盐1.3 纳米材料的结构10-11

11-12纳米材料研究现状现状12-15

1.5 过渡金属钒酸盐纳米材料研究

1.6 本课题的立题意义和主要内容15-16第二章 三维(3D)花状亚磷酸氢镍微/纳米结构的液相制备及其磁学性质研究16-2416-17

2.1 引言16

2.2 实验部分

2.4 三维亚磷酸氢镍花2.3 结果与讨论17-21

21-22状结构的热重分析学性质分析22-23

2.5 三维亚磷酸氢镍花状结构的磁

第三章 CTAB

3.2

2.6 本章小结23-24辅助的三维(3D)花状钒酸铜微24-32实验部分24-25质30-31

3.1 引言24

3.3 结果与讨论25-303.4 电化学性3.5 本章小结31-32第四章 水热法合成钒酸32-37

4.1 引言铜分等级的微米球及其电化学性质研究3233-36献38-43况44 4.2 实验部分32-334.4 本章小结36-37致谢

43-44

4.3 结果与讨论结论37-38

参考文

在学期间公开发表论文及著作情

第二篇：论文题目功能氧化物纳米材料的液相合成与性质研究

论文题目：功能氧化物纳米材料的液相合成与性质研究

作者简介：刘军枫，女，1979年10月出生，2002年9月师从于清华大学李亚栋教授，于2007年7月获博士学位。

中

文

摘要

金属氧化物纳米材料在催化、光电、气敏、磁性以及锂电池等领域有着广泛的应用前景。发展新的合成方法，探索其生长机制，从而获得具有特定尺寸、形貌、维度、单分散性等的纳米材料，对于深入系统地研究纳米材料与性能的关系，并进一步实现纳米材料的组装，构建功能纳米结构体系，最终使纳米材料进入应用领域具有重要意义。

本论文工作以金属氧化物及其复合氧化物功能纳米材料为研究主体，以液相合成为主要方法，致力于寻求适合纳米晶的调控合成方法，通过对反应过程、环境的控制实现具有不同尺寸、形貌，尤其是具有特定晶面、特定取向的含氧化合物纳米晶控制合成，探索纳米晶成核、生长与晶体结构间的规律性。并在此基础上，研究纳米晶形貌、表面结构与性质之间关系，寻找规律性，用于指导其他功能纳米材料的设计合成，为其将来的应用打下良好的基础。

发展了水热合成钒氧化物单晶纳米带的新方法，在对不同价态钒氧化物晶体结构差异进行了系统分析后，通过设计合理的化学反应，实现了对五氧化二钒、二氧化钒单晶纳米带的控制合成，验证了层状结构与纳米带形成的相关性。以偏钒酸铵为原料，通过水热反应的条件控制，制备了水合五氧化二钒V2O5单晶纳米带，方法简单，产率较高。基于水合五氧化二钒晶体本身的层状结构特点和纳米带的特殊性，设计制备了对乙醇气体有较高的选择性和稳定性的五氧化二钒纳米带气敏传感器，环境湿度和其他测试气体的存在对其干扰较小。制备了半导体氧化物（Fe2O3、TiO2和SnO2）纳米颗粒包覆的五氧化二钒纳米带。研究了纳米带的表面包覆对其气敏性质的改进，结果表明包覆后的纳米带比包覆前具有更高的灵敏度和稳定性，为新型传感器材料的设计制备提供了一种可行的思路。

将五氧化二钒一维纳米材料的水热合成方法扩展到合成低价钒氧化物体系中，通过在水热反应体系中加入一种温和的还原性酸，即采用水热还原的方法成功地制备了亚稳态单斜相的二氧化钒VO2(B)单晶纳米带。探讨了反应参数对产物晶相、形貌的影响及纳米带的生长机理。对二氧化钒VO2(B)单晶纳米带的电学疏运性质、磁学性质及锂电性质进行了研究。电学疏运性质测量显示VO2(B)单晶纳米带具有半金属特性，对于红外辐照可以产生电流响应信号，从而为其在纳米器件（如光开关等方面）上的潜在应用提供了实验依据。磁测量表明它是一种顺磁性材料。采用VO2(B)纳米带做电极制备的锂离子模型电池充放电电压稳定，循环性能很好。

在钒氧化物纳米材料的研究基础上将体系扩展到其复合氧化物的合成及性质研究。有机相中可分散的荧光纳米晶由于可以通过旋涂挥发有机溶剂的技术制备均匀的荧光薄膜，一直以来都受到人们的广泛关注。我们通过在水热反应体系中引入油酸分子，设计了水－油界面溶剂热反应体系，成功合成了稀土离子掺杂的荧光LaVO4单分散胶体纳米晶。所得的LaVO4纳米晶尺寸均匀，表面包覆一层键合油酸分子，可稳定分散于有机溶剂中，并在合适条件下自组装成有序结构。讨论了纳米晶的生长与自组装机理，以及油酸分子在反应体系中的多重作用，包括限制晶体生长、保持晶体稳定存在以及控制反应pH值等作用。Eu3+、Dy3+、Sm3+离子掺杂的LaVO4纳米晶在紫外光激发下可以发出红色、黄绿色荧光，因此使得这些纳米晶可以通过简单的旋涂等方式制备透明的荧光薄膜，甚至可以通过纳米晶的单层膜自组装进一步制备只有十几个纳米厚的薄膜，这对于制备微型柔性器件和防伪技术的应用具有重要意义。

在LaVO4胶体纳米晶的合成基础上进一步将此水－油界面溶剂热法发展为稀土正钒酸盐胶体纳米晶的通用合成方法，成功制备了包括LnVO4（Ln=Y、Lanthanide）等纳米晶的胶体溶液。探讨了稀土钒酸盐晶体结构对产物形貌的影响，以及胶体纳米晶的光学性质。

基于分散在有机溶剂中的纳米晶良好的成膜性以及稀土离子掺杂的LaVO4纳米晶的下转换荧光性质，将单分散LaVO4胶体纳米晶通过简单的涂敷技术制备成透明的荧光薄膜，应用于染料敏化太阳能电池中，明显的提高了电池的性能。掺杂Dy3+离子的LaVO4荧光薄膜可以替代紫外滤膜吸收对电池不利的紫外光，提高电池寿命，同时又可将紫外光下转换为能够被染料吸收的可见光，从而减少因紫外光损失而引起的效率降低。与未加紫外滤膜的电池相比，在电池背面添加一层LaVO4:Dy荧光滤膜显著地提高了电池的寿命和稳定性。而其下转换荧光可以被染料分子吸收，用于产生光电流，补偿了由于滤去紫外光产生的能量损失，与添加无荧光紫外滤膜的电池相比总效率提高了23.3%。

发展了一种基于非极性溶剂的新型的溶胶-沉淀的方法，以具有特定形貌和确定晶面的LaVO4和CeVO4纳米晶为载体，单分散Au溶胶为活性Au，设计制备了Au/LnVO4（Ln=La，Ce）催化剂，研究了其催化氧化CO反应的活性。金粒子的尺寸大小是影响催化剂活性的重要因素。通过油酸或油胺辅助的液相反应，成功合成了一系列尺寸确定的Au溶胶（2nm、5nm、7nm、11nm、13nm、16nm），负载之后Au粒子与载体LaVO4的形貌和尺寸可以得到保持。所制备的催化剂在室温下对CO具有很好的催化活性。由于Au粒子的尺寸大小可以在负载前完全确定，因此可以很容易的研究Au/LaVO4在催化反应中的Au粒子的尺寸效应，结果表明5nm-Au/LaVO4具有最高的催化活性。这种方法可进一步扩展到其他高活性的金催化剂及复合纳米材料的制备上。

建立了表面活性剂辅助的水热及溶剂热合成方法制备了一系列不同形貌的钒酸铋纳米结构。通过选用合适的表面活性剂及控制单体浓度，调控不同晶面的生长速度，获得了包括微米管、四方片、梳状分形等一系列不同形貌的BiVO4微米晶，并进一步研究了晶体生长与晶体本身对称性的关系，发现具有四方对称性的单斜相纳米晶正是从四方相晶体相变转化而来，证实了晶体结构与生长行为的对应关系。发展了油酸辅助的溶剂热法合成BiVO4纳米晶的新方法。通过对水油界面反应的设计，获得了高温稳定相白钨矿型的四方相结构BiVO4（s-t），并实现了BiVO4纳米棒及梭形纳米结构的合成。通过对水热体系pH值的控制成功制备了具有特殊形貌、取向的铌基钙钛矿结构纳米材料K4Nb6O17、KNb3O8、KNbO3，发展了醇/水混合溶剂制备KNbO3的溶剂热法，发现通过控制反应溶剂醇/水比例可以控制合成不同晶型的KNbO3，而所得到晶体的形貌又是与其本身的晶体结构密切相关的。

将研究体系扩展到其他金属氧化物纳米材料上，以两种非常重要的氧化物材料－氧化铁和氧化钛为例，尝试合成具有不同形貌的纳米材料，通过对材料性能的表征，研究材料形貌与性能之间的相关性。采用简单的水热反应制备了多种形貌确定的Fe2O3纳米晶，对比研究了其催化氧化CO的反应活性。结果显示催化剂的活性不仅与Fe2O3催化剂的尺寸大小、比表面积有关，而且与Fe2O3纳米粒子的暴露晶面有密切关系。具有更多活性面的催化剂整体的催化反应活性更高。此工作对设计合成实用催化剂具有一定意义。采用溶剂热法和水油界面法分别合成了单分散的过渡金属及稀土离子掺杂的TiO2纳米棒和纳米颗粒，并进一步采用一种基于微乳体系的方法将具有疏水表面的TiO2纳米晶组装成具有亲水表面的胶体球。由于纳米晶间长链有机分子的存在，此胶体球经高温退火可形成具有高比表面积的介孔材料，对于胶体球的催化性能和太阳能电池性能初步的研究结果显示了这种介孔材料的优异性能。这种方法为单分散纳米晶的形貌与性能研究以及进一步的应用打下了良好的基础。

关键词：

液相合成；功能氧化物；纳米结构 Functional Metal Oxide Nanomaterials: Solution-Based Synthesis and Property Investigation

Liu Junfeng

ABSTRACT

Metal oxide nanomaterials have exhibited promising applications in catalysis, sensing, optics, magnetism and batteries.Preparation of nanomaterials with well-defined size, morphology, dimensionality and diversity through novel synthesis approaches and investigations of their formation mechanism should be a key precondition to reveal the relations between the structures and properties, assemble the nanocrystals into superstructures and pave the way to the real applications.In this dissertation, valuable explorations have been carried out on new solution-based manipulated synthetic strategies for functional metal oxide nanostructures along with their formation mechanisms and novel properties, emphasizing on the relationship between crystal symmetry and morphology manipulation as well as the connection between properties and size/morphology of nanomaterials.A rational low-temperature hydrothermal synthetic way has been developed to selectively prepare vanadium oxide nanobelts with different valent status.The formation mechanism is investigated in details and believed to be closely related to their layered structure.A highly selective and stable ethanol sensor was designed based on the intrinsic layered structure of vanadium pentoxides and the advantages of nanobelts.Fe2O3、TiO2 and SnO2 nanoparticles coated vanadium pentoxide nanobelts were synthesized through a simple solution method.The gas sensor property of metal oxides nanoparticles coated vanadium pentoxide nanobelts was investigated and the result shows that coated ones are more sensitive and stable than uncoated ones.This approach opens up a new route in the research work for novel gas sensor.Metastable monoclinic vanadium dioxide single-crystal nanobelts were successfully synthesized by a direct hydrothermal reduction method.The morphology of the samples can be adjusted by varying the parameters of the solution.The investigation on the electrical transport and magnetic properties of vanadium dioxide nanobelts shows their potential applications in nanodevices.The electrical transport through single nanobelts showed that VO2(B)has a semimetal property and optoelectronic response in infrared radiation.It was also proved by the magnetic measurement that VO2(B)is a paramagnetic material.The lithium ion cell model fabricated by VO2(B)nanobelt showed stable voltage and excellent circulation performance.This hydrothermal method should be applicable for large-scale production of low-dimensional nanostructured vanadium dioxides.The systematic approach was extended to synthesis and property studies of metal composite oxides.A synthesis and self-assembly approach assisted with oleic acid molecules is developed to fabricate luminescent Ln3+ doped LaVO4 nanocrystals(NCs)and rare earth vanadates.As synthesized LaVO4 nanocrystals could be well dispersed in non polar solvent and self-assemble into ordered patterns due to long chain oleic acid molecule attached on the surface of the NCs.The growth and self-assembly mechanism as well as the multiple functions of oleic acid were investigated.There will be red or greenish yellow fluorescence emitted from Eu3+, Dy3+, Sm3+ doped LaVO4 nanocystal under UV excitation, which makes it possible that transparent fluorescent films can be made by simple spin coating method.Such a finding is significantly meaningful for the application of these nanocrystals on flexible devices and anticounterfeit technologies.A transparent luminescent film of uniform nanocrystals, which could absorb UV light and down-convert it to visible light, prepared by coating approach could greatly improve the cell performance when applied in dye-sensitized solar cells.Dy3+ doped fluorescent film can absorb UV light, which is unfavorable to solar cells, thus to improve the life of cells.At the same time, the UV light absorbed could be down-converted to visible light, which can be absorbed by dye molecules to generate photo electricity.By this means, the energy loss due to the absorbed UV light is compensated and the overall conversion efficiency was even improved by 23.3% vs.that of the solar cells without fluorescent film.Catalytically active gold catalysts have been designed via monodispersed gold colloids on LaVO4 nanocrystals with controlled size as more well-defined nanocatalysts.The size of the gold particles is a very important parameter to get active catalysts.A novel colloidal deposition method to prepare Au/LaVO4 nanocomposite catalyst with monodispersed Au colloids and uniform LaVO4 nanoplates in nonpolar solvent.Monodispersed Au colloids with tunable size(such as 2, 5,7, 11, 13, and 16 nm)and LaVO4 nanocrystals with well-defined shapes were pre-synthesized assisted with oleic acid/amine.During the following immobilization process, the particle size and shape of Au and LaVO4 were nearly preserved.As-prepared Au/LaVO4 nanocomposite showed high catalytic activity for CO oxidation at room temperature.Since sizes of gold particles were well-defined before the immobilization process, size effect of gold particles was easy to be investigated and the results show that 5nm-Au/LaVO4 nanocomposite has the highest activity for CO oxidation.This synthetic method can be extended further for the preparation of other composite nanomaterials.Bismuth vanadate micro/nanocrystals with different morphologies were synthesized by surfactant assisted hydrothermal/solvothermal methods.The studies on the crystal growth reveal the relationship between the crystal structures and the morphology.Low dimensional potassium niobate nanostructures with different compositions were achieved by simply controlling pH value of the hydrothermal system.It was found that the solvent plays an important role in the phase control of the KNbO3 nanocrystals.Study on the catalysis properties of iron oxide nanocrystals with different size and morphology showed that the catalytical activities were influenced not only by the size and BET of the materials, but also by the crystal planes due to the facts that t different active sites on certain reactions, varies with crystal planes.Redispersible TiO2 nanocrystals with hydrophobic surface were prepared by controlled solvothermal

reactions，followed

by

a

newly

developed microemulsion-based method to assemble the nanocrystals to colloidal spheres with hydrophilic surface.Mesoporous spheres, which are expected to show excellent properties in applications such as catalysis, could then be achieved by annealing of colloidal spheres.Key words:

Hydrothermal/solvothermal synthesis;Functional metal oxides;Nanostructures