Fabrication And Characterization Of One-Dimensional Nanostructures Of Functional Materials Via Electrospinning

Nanoscale one dimensional (1D) materials have been popular in the field of nanoscience and nanotechnology due to their novel electrical transport, optical and magnetic properties, and potential applications in nanoscale elelctronic evice, nanophotonics, sensors, energy storage and transform. Among these methods, electrospinning seems to provide the simplest approach to nanofibers with both solid and hollow interiors that are exceptionally long in length, uniform in iameter, and diversified in composition. Comparing with a number of processing techniques of fabricating micro fibers such as melt spinning, wet spinning and dry spinning, and nanofibers such as island spinning, template synthesis, etc., electrospinning offers several obvious advantages: (1) the process of fabricating nanofibers is simple and efficient; (2) the diameters of nanofibers fabricated can be easily controllable; (3) the range of the application is wide. In addition, these nanofibers may provide a connection between the nanoscale world and the macroscale world, since the diameters are in the nanometer range and the lengths are kilometers.In this dissertation, we combined electrospinning process with sol technique, sol-gel technique and gas-solid reaction, fabricated a series of inorganic, inorganic/inorganic and polymer/inorganic composite 1D micro-nanomaterials and the study of their properties.In the first section, we have successfully prepared one-dimensional micro-nanostructural EuOF, HoOF and PrOF by an electrospinning method combined with sol-gel technique. The pure one-dimensional micro-nanostructural EuOF, HoOF and PrOF composed of aggregates of small nanocrystals with average diameter of 45 nm. PL measurement demonstrated the remarkable luminescent properties of these materials, which permit it be exploited for optoelectronic nanodevices. Furthermore, High specific surface area of the production resulting from its rough surface and small diameters will be useful in a variety of applications. This method is general and can be expanded to the large-scale synthesis of other one-dimensional micro-nanostructural rare-earth oxyfluoride.In the second section, we have successfully prepared one-dimensional micro-nanostructural rare-earth ions doped TiO₂ by an electrospinning method combined with sol-gel technique. The micro-nanostructural rare-earth ions doped TiO₂ were composed of TiO₂: RE nanocrystals with an average diameter of 10 nm, which were smaller than that of the TiO₂ nanocrystals in the undoped TiO₂ nanofibers. The energy transfer from the surface traps of the TiO₂ nanocrystals to the crystal field states of the rare earth ion induced remarkable luminescent properties, which is probably applicable for the making of optoelectronic nanodevices.In the third section, we have successfully prepared porous ZnO/TiO₂ nanofibers by an electrospinning method combined with sol-gel technique. The holes were well-dispersed in the composite nanofibers which are due to the shrinkage of the TiO₂ and ZnO after removing PVP from the fibers and the fibers surface area increased obviously. The absorption feature suggests that the ZnO/ TiO₂ nanofibers can absorb more solar energy than pure TiO₂ nanofibers. Furthermore, SPS measurement demonstrated that the photics properties of porous ZnO/TiO₂ nanofibers advanced significantly compared with TiO₂ nanofibers, which permit it be useful in electrochromic, charge storge and photo-voltaic devices.In the last section, we have successfully prepared ZnS/PVA nanofibers by an electrospinning method combined with sol technique. The best homogenous dispersion of ZnS nanoparticles in nanofibers was as achieved at the molar ratio of 1:20. The coordination between–OH and Zn²⁺ prevented the ZnS nanoparticles from aggregating in the nanofibers. In addition, there is little change in the structure and properties of ZnS nanoparticles upon incorporation into the PVA fiber via electrospinning. Good photoluminescence property was observed for ZnS/PVA nanofibers, which could be utilized for fabrication of optoelectronic nanodevices. Furthermore, we have successfully prepared ZnS:Cu/PVA nanofibers and ZnS:Mn/PVA nanofibers by an electrospinning method combined with gas-solid reaction. PL measurement and luminescence decay time measurement demonstrated that the luminescence properties of Cu-doped and Mn-doped samples changed significantly compared with the un-doped sample, which was caused by the influence of Cu induced t₂ level and Mn induced ⁴T₁ level. Therefore, we anticipate that the composite nanofibers with good photo luminescence property can be exploited for fabrication of optoelectronic nanodevices.