【作者】 张传玲；

【导师】 俞书宏；

【作者基本信息】 中国科学技术大学 ， 无机化学， 2013， 博士

【摘要】 静电纺丝技术在制备一维纳米材料方面具有简单快捷、规模化、纤维形貌可控等显著的优势,特别是通过将功能化组分直接加入到电纺溶液中能够制备各种复合纤维,克服了许多传统合成方法的缺点。另一方面,在电纺碳纳米管等一维纳米材料时,发现碳纳米管在电纺纤维内会沿纤维轴向排列,因此利用静电纺丝技术组装一维纳米材料成为可能。迄今为止,尽管纳米材料表现出新颖的或者更好的性质,然而将纳米构筑单元大范围组装成功能性宏观材料、并保持组装体的稳定性仍是当前该领域的一个挑战。本论文将集中阐述如何通过静电纺丝技术实现电纺纤维与一维功能性纳米单元的有效复合、组装及组装体的性能研究。通过电纺各种一维纳米结构单元,成功制备了纳米复合纤维,充分证明了静电纺丝技术在大范围组装一维纳米结构单元方面的广泛适用性、稳定性及简单快捷性等特点；由电纺纤维和纳米结构单元构成的柔性自支撑无纺布具有可调控的光性能,并且在表面增强拉曼(SERS)及光热杀伤癌细胞等方面表现出很好的应用前景。取得的主要研究结果如下：1、发展了通过静电纺丝技术在聚乙烯醇(PVA)纤维内大范围组装金纳米棒的有效方法。研究发现,金纳米棒均沿着电纺纤维轴向排列,从而证明静电纺丝技术可有效地组装金纳米棒。与传统组装方法相比,本方法具有操作简便、可实现大规模组装等优点。通过改变电纺溶液中金纳米棒的浓度,可以调节电纺纤维内金纳米棒之间的距离,从而实现对电纺膜光学性能的调控。实验结果表明,与金纳米棒水溶液及相应的电纺溶液涂布膜相比,具有相同颗粒浓度的电纺膜的横向等离子体共振波长(TPB)和纵向等离子体共振波长(LPB)均明显红移；随着金纳米棒浓度的增加,复合薄膜的LPB则明显蓝移,并且宽化,而TPB没有明显变化,从而证明组装对其光学性质的影响。制备的AuNR/PVA复合电纺纤维薄膜可作为SERS基底进行应用。研究发现,柔性自支撑复合薄膜对3,3’-二乙基硫菁碘盐(DTTCI)分子有显著的SERS效应,在作为SERS基底进行应用时,具有高重现性及高稳定性等优点。此外,通过将PVA交联,制备的包覆有金纳米棒的复合薄膜有很好的光热效应：在808nm红外光照射下,尺寸为10×5mm2大小的复合膜在60s内即可将1mL水由23℃加热到50℃；将复合薄膜像创可贴一样直接覆盖在癌细胞培养基上,进行癌细胞杀伤性能测试。实验结果表明,大部分癌细胞在30s内即可被杀伤。由此证明制备的复合膜在杀伤癌细胞方面具有使用方便,效率高等优点。2、基于以上有关组装金纳米棒这种单组份纳米颗粒的基础上,展示了静电纺丝技术对复合纳米结构单元的组装。首先通过静电吸附成功制备由相同维度、不同材料组成的金纳米棒-银纳米线组装体。研究发现,金纳米棒在银纳米线两侧以头对头方式排列形成串状结构,通过控制金纳米棒与银纳米线的比例,可以改变银纳米线上金纳米棒间距离,从而实现对其光学性质的调控：进一步利用静电纺丝技术将这种组装体包覆在聚合物纤维内并进一步排列,使金纳米棒-银纳米线组装体沿着电纺纤维轴向排列,实现二次组装。对制备的电纺薄膜进行了光学表征,发现与复合纳米颗粒溶液及涂布膜相比,相应的电纺薄膜的LPB明显红移,并且峰变宽。同样对几种基底进行SERS研究,发现具有相同量的金纳米棒-银纳米线组装体的电纺膜比相应的涂布膜表现出更强的SERS效应以及更好的稳定性,进一步证明了组装对复合纳米纤维膜性能的促进作用。另外,制备由相同材料组成的Au/SiO2/Au复合纳米结构单元,通过静电纺丝技术将其固定在聚合物纤维内并对其排列,制备复合功能薄膜,研究Si02层的刻蚀程度对复合薄膜性能的影响。3、进一步发展了利用磁场辅助的静电纺丝技术大范围组装超长纳米线。首先将制备的高长径比银纳米线进行电纺后,发现银纳米线被很好地包覆在PVP电纺纤维中,并且均沿着纤维轴向平行排列；通过改变电纺溶液中银纳米线的浓度,可调控单根电纺纤维内银纳米线的数量：利用磁场辅助的收集技术进行收集,可获得由平行排列的电纺纤维组成的电纺薄膜,从而实现整个纳米纤维膜中银纳米线的平行排列。另外利用聚合物本身的柔软性,制备了具有不同交叉角度的膜状材料和螺旋结构的纤维组装体。相邻的银纳米线之间存在着电磁场,通过改变入射光的偏振角度可以调控电纺薄膜的紫外-可见光谱,进一步证明了静电纺丝技术对银纳米线的有效组装。此外,静电纺丝超细碲纳米线,证明静电纺丝技术不但可以大面积组装银纳米线这种刚性较强的一维材料,而且可以排列像碲纳米线这种超细柔性一维材料。研究发现,选择碲纳米线不能很好分散地溶剂配置电纺溶液时,静电纺丝之后碲纳米线以束状组装体包覆在聚合物纤维内,并沿着纤维排列,形成具有核-壳结构的复合纤维。由于碲纳米线本身具有很高的反应活性,且小分子可渗透过聚合物到达纤维内部,制备的复合纤维可作为微型反应器进行应用。更多还原

【Abstract】 Electrospinning technique can facilely fabricate one-dimensional (1D) nanomaterials on a large scale and the morphology can be controlled, especially a variety of composite nanofibers can be synthesized by directly adding functional components into the electrospinning solution, which overcomes the disadvantage of the conventional synthesis methods for1D nanomaterials. On the other hand, several reports found that anisotropic nanostructures, such as carbon nanotubes, were aligned along the axis of the electrospun fibers, thus it is possible to use electrospinning technique as a kind of assemble method. So far, although the nanomaterials have superior properties to those of their bulk counterparts, it still remains a challenge that assembling of these individual nanocomponents into macroscopic materials in a large scale and keeps the stability of the assemblies.This dissertation will focused on combining and assembling1D functional nanounites effectively with electrospun fibers by electrospinning technique, and the properties of the1D composite nanofibers were investigated. By electrospinning several kind of ID nanounites, composite nanofibers were successfully fabricated, which confirms the electrospinning technique could assemble1D nanounites in large scale and has the advantage of broad applicability, efficiency and stability. The main results can be summarized as follows:1. A novel assemble route was developed for aligning gold nanorods (AuNRs) within polyvinyl alcohol (PVA) fibers by electrospinning technique. After electrospinning, AuNRs were confined within the PVA fibers and aligned along the axial of the electrospun fibers, which confirms AuNRs can be effectively assembled by elelctrospinning technique. Compared with some traditional assemble methods, electrospinning technique has shown obvious advantages in simple operation and can assemble on a large scale. By varying the AuNRs concentration in the electrospun solution, the space among the AuNRs confined within the polymer fibers could be adjusted and therefore the optical properties of the AuNR/PVA electrospun mats could be controlled. Compared with the AuNRs solution and corresponding casting films, both the transverse Plasmon band (TPB) and the longitudinal Plasmon band (LPB) of the electrospun mat red shifted; when increasing the AuNRs concentrations, the LPB of the electrospun mats blue shifted and broadened, while there is no significant change on TPB, which confirms the effect of assemble on their optical properties. In addition, the electrospun mat could be used as surface enhanced Raman scattering (SERS) substrate. The resulting electrospun mat makes a significant SERS enhancement to3,3’-diethylthiatricarbocyanine iodide (DTTCI) molecules with large-area uniformity and good reproducibility. Lastly, PVA electrospun fibers were crosslinked, and the composite films have remarkable photothermal effect. Under808nm irradiation, the composite film with dimension of10×5mm2could heat1mL water from23℃to50℃in60s, and most of the cancer cells could be injured in30s, which confirms the Au/PVA composite films have the advantage of high efficiency and can be used facilely.2. Composite nanounites were electrospun and assemble within the polymer fibers. Firstly, we fabricated the nanocomposites composed of the same dimensional but different components, such as AuNR-AgNW assemblies, in which the AuNRs were arranged along the axis of the AgNWs with a preferential string-like alignment. The assembled AuNR-AgNW nanocomposites are then further embedded within PVA nanofibers by electrospinning, by which both AuNRs and AgNWs can be stabilized and arranged along the axis of polymer nanofibers. The influences of the AuNR-AgNW assemblies with different AuNRs concentrations on the optical properties and SERS enhancement have been investigated. Compared with the normal casting films composed of randomly dispersed AuNRs and AgNWs, or electrospun mats with monometallic components, the resulting AuNR-AgNW/PVA electrospun mats show red-shifted and broader absorption bands, also higher SERS performances, due to the order alignment of AuNR-AgNW nanocomposites on a large scale. Secondly, electrospinning was used to assemble the nanocomposites composed of the same components, such as Au/SiO2/Au nanoparticles. The nanocomposites were also aligned within the electrospun fibers, and the performance of the composite mats could be varied by etching the SiO2layer.3. Ultralong NWs were further macroscopic-scale aligned by using the magnetic-field-assisted electrospinning technique. With this method, ultrolong AgNWs can be assembled within the PVP electrospun fibers and arranged in parallel; The number of AgNWs confined within the PVP fibers can be controlled by changing the concentration of NWs within the electrospun solution; While the polymer nanofibers can also be arranged by the magnetic-assisted-field electrospinning technique, the AgNWs were manipulated to align parallel to each other throughout the entire film. The AgNWs can be further aligned as a result of the flexibility of the polymer fibers, and mats with tunable cross angle and the fiber assemblies with hierarchical structures can be prepared. Due to the high EM field existing in adjacent AgNWs, the polarization angle of the incident light strongly influences the UV-vis transmission spectra for the mats, which further confirms the effectively assemble of NWs by electrospinning technique. In addition, ultrathin TeNWs were electrospun to confirm that the electrospinning technique could not only assemble rigid NWs, but also the flexible ones.When chosing the non-benign solvent of TeNWs to solve the polymer and electrospinning, the TeNWs could be assembled like a bundle within the electrospun fibers. The obtained composite fibers could be used as microreactor, as TeNWs have high reactivity.更多还原