Fabrication And Field Emission Performance Of Oriented One-dimensional Nanomaterials By Using AAO As Templates

Fabrication strategies of one-dimensional(1D) nanomaterials including sol-gel, vapor deposition, electrospinning, etc. have been established and developed in the past decades since they are used widely in electrical, optical and other fields. However, it is still a great challenge to prepare oriented 1D nanomaterial with programmable structures. In this thesis, therefore, the oriented TiO2 nanotubes or nanorods were obtained successfully with the combination of “hard template”(Anodic Aluminum Oxide, AAO) and “soft template”(i.e. the phase separation of polymer blend or microphase separation of block copolymer) or spin-coating method. Structures of obtained materials have been characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM) and X-ray diffraction(XRD). Our results indicate that the content of the precursor(i.e. titanium-tetraisopropoxide, TTIP, the precursor of TiO2), weight fraction of the blend(or the block in copolymers) have significant effect on the resultant structures. Novel TiO2/ZnO composite nanomaterials were prepared based on the oriented TiO2 nanotubes by “second spin-coating” or “hydrothermal reaction”. Furthermore, the performance of obtained 1D nanomaterial was discussed by taking field emission for example.In the first part, the oriented TiO2 nanotubes/nanorods were prepared by the combination of AAO template and direct spin-coating. After the spinning-coating of TTIP, the TTIP/AAO composite was calcinated at 450oC, which was followed by the remove of AAO template by the solution of NaOH. The structure of TiO2 nanotubes is under the control of TTIP%, the calcination temperature and other parameters. Moreover, the performance of obtained oriented 1D nanomaterial in field emission has been investigated. O ur results indicate that the size of TiO2 nanocrystal play an important role in the performance.In the second part, composite TiO2/ZnO nanomaterials were prepared by means of “two-step” method. After the fabrication of oriented TiO2 nanotubes in the first part, ZnO(or the precursor of it) was loaded on them by second spin-coating or hydrothermal reaction. In the case of “second spin-coating”, there are double-layer structures including outer-TiO2 and inner- ZnO. Relative to the neat TiO2 and neat ZnO, the composite materials show enhanced performance in UV-vis spectrum. In the case of “hydrothermal reaction”, novel composite TiO2/ZnO materials with inner-TiO2-nanorod and outer-ZnO-nanoneedle can be obtained.In the third part, the oriented TiO2 nanotubes/nanorods were fabricated by the combination of “soft template” and “hard template”. The blend solution of PS/PEO/TTIP in chloroform was induced to the channel of AAO by means of capillarity, followed by the calcination and removal of AAO. In this easy way to prepare the oriented TiO2 nanomaterials, the dependence of TiO2 nanocrystal size and resultant performance in field emission on the TTIP% and weight fraction of polymer blend has been investigated systemically.In the last part, the oriented TiO2 nanomaterials were prepared by the combination of microphase separation of PS-b-PEO block copolymer and AAO template. The AAO channels were also filled with the blend solution of PS-PEO/TTIP(in chloroform) via capillarity. Then, the composite materials were calcinated to remove the polymer and transfer TTIP to TiO2. After releasing the AAO template, we can get the oriented TiO2 nanotubes/nanorods. O ur results indicate that the structure and resultant field emission performance depend crucially on the concentration of the solution and the weight fraction of PS(or PEO) in the copolymer.