电纺丝纳米纤维的制备.doc

1、附件 2论文中英文摘要格式作者姓名： 伍晖论文题目 ：电纺丝纳米纤维的制备、组装与性能作者简介 ：伍晖，男，1983 年 1 月出生， 2004 年 9 月师从于清华大学潘伟教授，于 2009 年 7 月获博士学位。中文摘要一维纳米材料在光电、传感、磁性、仿生以及纳电子器件等领域有着广泛的应用前景。发展新的合成与组装方法，大规模的制备具有特定尺寸、形貌、维度和取向的一维纳米材料，深入系统地研究纳米材料的结构与性能的关系，并进一步构建一维纳米结构功能器件，对于使纳米材料最终进入应用领域具有重要意义。 本论文以电纺丝为平台， 制备了多种功能无机、金属、高分子材料的一维纳米结构，研究了纳米结构的定向

2、组装和物理性质，并探索了这些纳米结构在传感、微电子器件、仿生表面等方面的应用，取得了一些有意义的结果：（ 1）过渡金属氧化物具有丰富的价态和价电子层构型，可广泛应用于催化、传感、电子等领域。 过渡金属氧化物的一维纳米结构具有大的表面积和特殊的 各向异性结构，在微电子器件、纳米激光器、紫外响应开关、高灵敏度气敏传感器等方面具有大的应用前景。因此，金属氧化物一维纳米结构的合成和组装是纳米材料研究的重点和热点之一。本论文将电纺丝技术与溶胶 - 凝胶法相结合， 制备了均匀连续的氧化物纳米纤维，并系统的研究了氧化物纤维受前驱体溶液、热处理温度等工艺因素的影响。通过对工艺参数的调整，我们实现了对纤维直径的

3、有效控制。在此基础上，对电纺丝设备进行了设计和改装，实现了对电纺丝纤维取向的控制，获得了排列整齐的氧化物纳米纤维阵列。我们还采用预制模板法和化学腐蚀的方法，成功的合成了具有多孔结构的氧化物纳米纤维。 多孔氧化物纳米纤维拥有更大的表面积， 因而有望能体现出更好的传感、催化、吸附等性能。（ 2）一维纳米结构是电子有效传输的最小维数的结构，是研究电子输运行为的尺度和维度效应的理想系统。在过去的十年中，碳一维纳米材料（主要为碳纳米管）的合成和电学性能研究获得了长足的进展。而其他非碳材料的无机半导体一维纳米材料的光电性质也得到了广泛的关注。本论文系统的研究了半导体氧化物纳米纤维的光、电性能。根据光致发光

4、谱，确定用电纺丝方法制备的氧化锌纳米纤维的禁带宽度为3.3eV ，我们利用原位操纵透射电子显微镜（In-situ TEM）和高灵敏度电流计的联用研究电纺丝氧化锌多晶纳米线的电学输运特性。观察到氧化锌纳米纤维电学输运特性的电子束响应。在没有电子束辐照情况下，氧化锌纳米纤维内部载流子浓度为1.2 10 15cm-3 ，电子束照射时，价带电子被激发，载流子浓度上升为1.0 1016 cm-3 。本论文还利用氧化物纳米纤维的半导体特性，成功组装了氧化锌纳米纤维沟道n 型场效应晶体管和CuO纳米纤维沟道的p 型晶体管，并获得了ZnO/CuO 纳米线交叉结构p-n异质结二极管器件。（3）发现了电纺丝制备的

5、TiO2 纳米纤维异乎寻常的室温超弹性。首先，在宏观体（纳米纤维薄膜）中发现了室温柔韧性。通过原位透射电子显微镜操纵，进一步证实了单根纳米线具有超弹性。 在外力作用下， TiO2 纳米纤维能够承受高达60%以上的局部应变而不断裂。 推断TiO2 纳米纤维的超弹性与其在外力作用下的相变有关，并在此基础上提出了可逆相变的机理，用以解释TiO2 纳米纤维的柔韧性。并利用选区电子衍射（SAED）、高分辨透射电子显微镜（HRTEM）、微区拉曼光谱（ Raman）、电学性能测试等多种分析表征手段，从多个角度证明上述理论，为相变机理提供了多方面的实验支持。具有高度柔韧性的氧化钛纳米纤维在柔性光催化薄膜、柔性

6、太阳能电池、柔性光敏传感器等方面具有好的应用前景。（4）作为新兴半导体材料，族氮化物（包括GaN、AlN、InN、 AlGaN、GaInN、AlInN和 AlGaInN 等）禁带宽度覆盖了红、黄、绿、蓝、紫和紫外光谱范围，在高性能微电子/ 纳电子器件中具有重要的应用。 族氮化物一维纳米结构的合成主要有化学气相沉积和模板法，其大规模合成和可控组装尚面临着大的挑战。基于电纺丝技术，提出一种新的族氮化物半导体一维纳米结构的合成和组装的方法，并研究了族氮化物纳米纤维的光、电、传感特性。通过氨化反应，在电纺丝氧化物纳米纤维的基础上反应合成连续、均匀的GaN和 InN 纳米纤维及其取向阵列。该合成方法具有

7、工艺简单、成本低、效率高的特点。本论文还研究了GaN的光、电学性质。通过光致发光谱测定 GaN纳米纤维的禁带宽度为 3.42eV，利用取向的纳米纤维组装得到单根 GaN纳米纤维沟道 n 型场效应晶体管器件。研究了 GaN纳米纤维的输运特性受外场的影响，利用多晶 GaN纳米纤维获得了高响应灵敏度的紫外探测传感器器件。初步探索了 GaN纳米纤维的元素掺杂，证明了室温下掺杂 Mn元素的 GaN纳米纤维具有铁磁性能，这一研究成果为室温稀磁半导体材料提供了新的合成方法。（ 5）一维金属纳米结构具有独特的各向异性结构，因而具有更加特殊的电学、磁学、力学、光学等物理性质。本论文通过多元化的实验设计，合成了多

8、种金属一维纳米结构，并研究了这些纳米材料的物理性能和应用。通过对氧化物前驱体纳米纤维的化学还原，获得了连续、均匀的金属 Cu、Fe、Co、Ni 等单质纳米纤维。铜纳米纤维的电学研究结果证明，受纳米晶界散射等因素的影响， Cu纳米纤维的电导率为 5 103S/cm，低于块体材料。本论文还研究了 Fe、Co、 Ni 纳米纤维的磁学性能。由于纳米尺寸效应， Fe、Co、 Ni 纳米纤维的矫顽力比传统块体材料提高两个数量级以上，分别为 427Oe， 651Oe 和 124Oe。我们在取向排列的 Ni纳米纤维阵列中发现了磁性各向异性。 探讨了金属纳米纤维在电磁波吸波的应用。 我们证明，Co纳米纤维添加能

9、够显著提高电磁波吸收材料的性能， 3%的添加量能够提升材料的吸波性能50%以上。在金属纳米纤维电学、 磁学性能研究的基础上， 进一步探讨了金属纳米纤维在催化、传感、吸波等方面的应用。 实验证明， Co纳米纤维添加能够显著提高电磁波吸收材料的性能，3%的添加量能够提升材料的吸波性能 50%以上。本论文还同时发现 Ni 纳米纤维具有很高的催化活性，可以用于催化生长 GaN纳米线阵列。除了单质金属纳米线，我们还通过热分解获得了 Ag/NiO 复合纳米纤维。 Ag/NiO 复合纳米纤维表现出了高的电导率，因而有望在纳米尺度电子元器件中充当连接导线的作用。通过将电镀与高分子纳米纤维结合，获得了空心结构的

10、金属纳米管道。金属纳米管道在表面拉曼增强（ SERS）领域有着出色的应用。实验表明，多孔结构的金属纳米管道可以探测到浓度为 10-8 M的探针分子。（ 6）仿生材料学以阐明生物体材料结构与形成过程为目标， 用生物材料的观点来思考人工材料，从生物功能的角度来考虑材料的设计与制作。以电纺丝高分子纳米纤维为基础，研究了纳米纤维仿生结构，通过对纳米纤维的可控组装，实现了多种具有特殊表面浸润特性的仿生表面。本论文还利用电纺丝制备了随机取向的聚乙烯醇缩丁醛 (PVB)纳米纤维网络， 系统研究了纤维形貌与疏水性能之间的关系，发现 PVB纳米纤维网络具有类荷叶表面的强疏水特性。证明，当 PVB纤维平均直径从

11、600nm变化到 100nm时，薄膜接触角从 130o 上升到 145o。这一结果与 Wenzel 模型和 Cassie 模型的预言相符。经过进一步的材料结构设计，本论文将纳米纤维排列为平行阵列，由于平行和垂直纤维阵列方向上不同的能量势垒，产生了表面润湿性各向异性，从而获得了仿竹叶结构的双向异性疏水表面。在与纤维阵列平行的方向获得了 142o 的静态接触角， 而垂直方向的接触角为 83o 。基于对纤维阵列各向异性能量势垒的进一步设计，对电纺丝设备接收装置进行了改装，获得了扇形排列的纳米纤维阵列，得到了仿羽毛结构的三向异性疏水表面。本论文还利用疏水纳米纤维组装成功人工仿生水黾，在水面上获得了高达

12、 205dynes/cm 的支撑力。关键词：纳米纤维；电纺丝；过渡金属氧化物；仿生材料Electrospinning of Functional Nanofibers: Synthesis, Assembly andPropertiesWu HuiABSTRACTThe design, preparation and controlled assembly of functional one-dimensional (1D) nanostructure has attracted considerable attention due to their unique electrical, op

13、tical and magnetic properties, which is different from that of bulk and nanoparticles, and their potential applications in optics, optoelectronics, catalysis and sensors. Nanowires or nanofibers offer the opportunity to investigate electrical and mechanical properties in size-confined systems, with

14、the possibility of providing a deep understanding of physics at the nano-scale. The main challenge in this area is how to precisely control the sizes, dimensionalities, compositions and orientations of nanowires, which may serve as a powerful tool for the tailoring of physical/chemical properties of

15、 materials in a controllable way. In this dissertation, valuable explorations have been carried out on the new synthetic and assembly of functional nanofibers via electrospinning. The physical properties and practical applications of these nanostructures have also been investigated.Cermic Nanofibers

16、We fabricated semiconductive oxide and nitrate nanofibers using a simple electrospinning method combined with sol-gel processing and post heat treatment. The synthesized nanofibers had diameters below 100 nm, and length over 1 cm. The morphologies of the oxide nanofibers including diameters and surf

17、ace roughness can be tuned easily. Highly oriented ceramic nanofibers with a length of several centimeters were fabricated using a newly modified electrospinning method.Copper oxide nanofibers with diameter of 60 nm and length of several hundreds ofmicrometers were fabricated via electrospinning met

18、hod. By using a designed fiber collector, the electrospun CuO nanofiber was deposited bridging two paralleled electrodes. Electrical measurement was conducted between the two electrodes. The conductivity of individual CuO nanofiber was measured to be 3*10 - 3 S/cm. Field effect transistor (FET) beha

19、vior in single CuO nanofiber was also observed, showing that CuO nanofiber was intrinsic p-type semiconductor. Our results indicated that semiconductive ceramic nanofibers can be directly assembled into FETs using the simple and versatile electrospinning method. The nanofiber transistors should be u

20、seful in building low-cost logic and switching circuits, as well as highly sensitive chemical and biological sensors with reduced device dimensions.A ZnO nanofiber FET was assembled by electrospinning. Uniform ZnO nanofibers with a diameter of 70 nm and length over 100 lm were first synthesized by e

21、lectrospinning. Using two paralleled electrodes as fiber collectors, we successfully placed a single ZnO nanofiber on the electrodes, and an FET device was fabricated based on the assembled nanofiber. An electrical transport measurement was conducted on the FET device, showing that ZnO nanofibers ar

22、e intrinsic n-type semiconductors.Present study on the optical and electrical transport properties of these semiconductive oxide nanofibers demonstrate that electrospinning can potentially be used as a straightforward and cost-effective means for the assembly of one-dimensional nanostuctures for bui

23、lding integrated nanodevices for various applications, such as transistors, sensors, diodes, and photodetectors.High-quality GaN nanofibers have been synthesized by in situ ammonization of electrospun gallium oxide nanofibers. Typically, the synthesized GaN nanofibers were polycrystalline, with a di

24、ameter of 40nm and a length of over a centimeter. The room temperature PL spectrum for the synthesized GaN nanofibers displayed a broad emission peak at 3.42 eV (363 nm), and the electrical characterization of a single GaN nanofiber showed an intrinsic n-type semiconductivenature. These polycrystall

25、ine GaN nanofibers were applied in UV-light sensors, which exhibited superior performance in sensitivity, response speed, and reversibility. This simple solution-based synthetic method also allows convenient assembly and precise doping of Mn or other elements into the GaN matrix within these 1D nano

26、structures and the Mn-doped GaN nanofibers show ferromagnetic character at room temperature. This approach is also applicable to the synthesis of other nitride nanofibers such as InN and InGaN. It is expected that this technique will make possible the large-scale production and assembly of nitride f

27、unctional nanomaterials with practical applications.The mechanical properties of oxide nanofibers were studied. We found novel super-elastic properties in TiO2 nanofibers. The mechanisms in this interesting phenomenon were discussed.Metallic Nanofibers and NanotubesA general synthetic method has bee

28、n developed to fabricate and assemble ferromagnetic transition metal nanofibers. By employing the novel electrospinning technique followed by subsequent heat treatment, we have successfully prepared uniform nanofibers of Fe, Co, and Ni with diameters of 25 nm and lengths longer than 100 m.Using a sp

29、ecially designed fiber collector, we can conveniently assemble magnetic nanofibers into aligned arrays. The electrospun magnetic metal nanofibers had unique magnetic properties, with much enhanced coercivitiesrelative to bulk materials. The outstanding features of this approach to get one-dimensiona

30、l magnetic nanostructure were its simplicity, effectiveness, and convenience of assembly. Therefore, electrospun magnetic nanofibers can potentially be used in fabrication of high density magnetic recording, magnetic sensors, flexible magnets, and spintronic devices. Silver/NiO composite nanofibers

31、were firstly synthesized by electrospinning. Synthesis of silver-based conductive nanofibers by the novel electrospinning technique has the following advantages: (i) The synthesis process is simple, low-cost, and environmentally friendly, with no template removing steps needed.(ii) Uniform nanofiber

32、s with length over 200 m are readily produced. (iii) The prepared nanofibers have an ultrahigh conductivity of 0.5*10 5 S/cm, which is much larger than that of electrospun nanofibers (10-6 to 0.4 S/cm) reported before. These highly conductive nanofibers can be further explored to fabricate interconn

33、ects for future nanoelectronic devices. (iv) These electrospun fibers can be easily assembled into aligned arrays by using a modified fiber collector. An easy assembly of these conductive nanofibers is important for further device uses. (v) The diameter of Ag/NiO fibers is at nanoscale, which dictat

34、es their superior performance as chemical sensors.Anisotropic and hierarchical Cu nanotubes with evenly distributed nanoscale pores on sidewalls were fabricated by electrodeposition on polymer nanofibers templates followed with chemical etching. Beneficial from high surface area and evenly distribut

35、ed nanopores, the synthesized hierarchical Cu nanotubes had high surface-enhanced Raman scattering (SERS)activities. The concentration study with CV revealed that the minimum concentration which can be detected on these hierarchical nanotubes was 1.0 10-8 M. This synthetic process is simple, inexpensive, effective, and therefore is a suitable methodology for large-scale producing of reliable and reproducible SERS substrates.Polymer NanofibersBiologically inspired systems allow us to get a deep understanding of nature, and provide new ideas for designing and fabricating soft material