【作者】 辛毅；

【导师】 黄宗浩；

【作者基本信息】 东北师范大学 ， 物理化学， 2009， 博士

【摘要】 一维半导体纳米材料,将在光电纳米器件方面有广泛的应用前景。文献报导了大量的有关纳米纤维、纳米线、纳米棒、纳米带、纳米管、纳米螺旋和纳米环的合成和制备技术。在这些技术中,静电纺丝法被认为是最简便的制备实体或中空纳米纤维的技术。并且,所制备的纳米纤维长度长,直径均匀,成分可变。电纺纤维具有比表面积大等优点,这使它们适合多方面的应用,如:过滤、传感器、催化、组织工程和防护服。目前,已有多于50多种高分子通过溶液电纺或熔融电纺被成功的制成超细纳米纤维。但很多共轭高分子受到分子量和/或溶解度的限制而很难直接电纺。在共轭高分子中,PPV因为其优良的光致发光、电致发光、光伏转换、光电导和非线性光学特性而受到广泛关注。另外,PPV光电器件的性能可通过与无机纳米粒子复合来改进。因此,如果能将PPV制备为高度取向和规整的结构,它将是纳米科学和技术中最吸引人的有机材料之一。PPV可以通过电纺它的聚电解质前驱物,再经热处理得到纳米纤维。但是,由于前驱物的聚电解质性质,电纺射流会经历更强烈的不稳定性。在本文中,我们展示了PPV的控制电纺,其中包括控制纤维的形貌、成分和功能。另外,我们制备了具有高光电转换特性的PPV/CdSe体异质结复合纳米纤维和具有超顺磁性能和良好光电性能的PPV/Fe3O4复合纳米纤维(单根或阵列形式),并将其组装成了模型器件,测试了相关性能。进一步的深入研究以及其它成分的体异质结单纤维模型器件的研制正在进行中。(1)以对氯苄和四氢噻吩为原料,制备了各种浓度的聚对苯乙炔前驱高分子的乙醇溶液,并系统探究了其物理参数(粘度、电导率和表面张力等)对所得纤维形态的影响,从而揭示了溶液本身物理性质对纤维形态影响的相关信息,为进一步控制电纺PPV纤维奠定了基础。(2)通过调控前驱物的溶液性质(粘度、电导率和表面张力)和电纺参数(纺丝电压、电纺距离和收集板种类),我们制备了不同形貌的PPV纤维,如纱线形、螺旋形和直线形。并且,通过改进电纺装置,我们得到了PPV纤维阵列和PPV核壳纤维。另外,将电纺与器件组装相结合制备基于单根电纺纤维的模型器件。(3)利用现代分析测试手段(扫描电子显微镜、透射电子显微镜和荧光光谱等)对所得纤维进行表征。研究了影响PPV纤维形貌和性质的因素。同时,揭示了高分子纳米纤维材料在设计合成以及在发光、光电转换应用过程中存在的关键基础科学问题。(4)将CdSe纳米晶或Fe3O4纳米粒子与PPV复合制备体异质结或多功能的纳米纤维(单根或阵列形式),并将其组装成模型器件。测试研究纤维的光电转换、磁学等性能。此项研究展示了PPV基电纺纤维可以直接简便的组装成单根及阵列纤维模型器件,推进了具有光电特性的共轭高分子纳米材料的实用化进程。更多还原

【Abstract】 One-dimensional (1D) semiconductor nanomaterials, which represent a unique system for exploring phenomena at the nanometer scale, are opening up substantial opportunities for novel photonic and electronic nanodevices. A large number of synthetic and fabrication methods have already been demonstrated for generating 1D nanostructures in the form of fibers, wires, rods, belts, tubes, spirals, and rings from various materials. Among these methods, electrospinning (a drawing process based on electrostatic interactions) seems to provide the simplest approach to nanofibers with both solid and hollow interiors that are exceptionally long in length, uniform in diameter, and diversified in composition. The high surface area-to-volume ratio of the electrospun fibers makes them suitable for many applications such as filtration, sensing, catalysis, tissue engineering, and protective clothing. Currently, more than 50 different polymers have been electrospun into ultrafine fibers in solvent solution or in melt form. Many conjugated polymers are difficult to be directly electrospun as limited by their molecular weights and/or solubilities.Among the conjugated polymers, poly(p-phenylene vinylene) (PPV) is particularly attractive in that the polymer exhibits excellent photo- and electroluminescence, photovoltaic, photoconductive, and nonlinear optical properties. Additionally, the performance of photovoltaic devices based on PPV can be enhanced by incorporating of inorganic nanoparticles. Therefore, PPV could be one of the most interesting organic materials in nanoscience and technology if it is possible to fabricate PPV into well-aligned and highly ordered architectures. PPV can be fabricated into nanofibers by electrospinning its polyelectrolyte precursor solution and subsequently with thermal conversion. However, the electrospinning precursor jets undergo intense instability due to its polyelectrolyte nature. In this work, we describe the controlling electrospinning of PPV nanofibers, witch including the controllment of the morphology and compositon of PPV nanofibers. In addition, we prepared PPV/Fe3O4 and PPV/CdSe nanofibers, and assembled them into devices. The properties of these fibers and devices were investigated. The deep investigation and the preparation of individual fiber devices based on other components (such as PPV/TiO2) are under way.Detailed content:(1) The precursory PPV solutions in ethanol with different concentration were synthesized from alpha, alpha’s-dichloro-p-xylene and tetrahydrothiophene. Moreover, in order to establish basic for preparing composite nanofibers, the physical parameters (concentration, conductivity, surface tension, etc.) affecting the morphology of ultrafine fibers was explored. As a result, the relational information about the effect of solutions’physical properties on the morphology of nanofibers was opened out.(2) By tuning precursor solution properties (viscosity, conductivity and surface tension) and processing variables (voltage, distance between the tip and collector, the kind of collector), we obtained uniform PPV fibers with various morphologies, such as yarns, helix and linear. In addition, by modifying the electrospinning process, we obtained the PPV fiber arrays and core-shell fibers. The individual electrospinning nanofibers were obtained, and were assembled into devices directly.(3) The fiber samples were characterized by using modern analysis and testing means (SEM, TEM, PL, etc.). In addition, the tropism mechanism and affecting factors of the morphology and properties of the fibers were researched completely. Simultaneously, the basic science problems obout the design and preparation of polymer nanofibers, as well as theluminescence and photoelectricity conversion in practical applications were opened out.(4) We prepared PPV/Fe3O4 and PPV/CdSe nanofibers, and assembled them into devices. The properties of these fibers and devices were investigated. Our results indicated that PPV-based nanofibers can be directly assembled into photoconductor devices using the simple and low-cost method.更多还原