Nanofibers are solid fibers with a nanoscale diameter, theoretically unlimited length and great potential to be used in many applications. In recent years, nanofibers from inorganic materials have become more established, with titanium dioxide (TiO2) attracting the most attention due to its thermal and chemical stability, excellent optical properties and non-toxicity. In nature, TiO2 has three crystalline phases: anatase, rutile and brookite. TiO2 shows great potential for application as photocatalyst to treat pollutants in wastewater and also in wound healing, tissue engineering and photodynamic therapy in cancer treatment. In this master’s thesis, the aim was to produce and evaluate inorganic nanofibers based on TiO2.
The first step in the master’s thesis was to optimize development of polymeric nanofibers with the electrospinning method from polyvinyl pyrrolidone (PVP) solution in absolute ethanol. Inorganic nanofibers with TIO2 were then fabricated from a PVP solution in ethanol with added titanium (IV) isopropoxide (TIP) and acetic acid with and without the addition of platinum and iron. Prepared nanofibers underwent the calcination process in an inert atmosphere to produce TiO2 nanofibers and in an ammonia atmosphere to produce titanium oxynitride (TiOxNy) nanofibers. The effect of composition of the polymer solution, the process parameters and the calcination on nanofiber morphology, the diameter and the crystalline phase by scanning and transmission electron microscopy, thermogravimetric analysis, energy dispersive spectroscopy and x-ray diffraction were investigated.
Results showed that the nanofiber diameter increases with increasing PVP and TIP content and decreases with increasing voltage. The calcination process also results in the decrease of the nanofiber diameter due to polymer elimination and in a rough surface due to crystallization of TiO2. During calcination nanofibers retain their primary structure. Results showed that when calcined at 400 °C, TiO2 crystallized in the anatase phase and when calcined above 800 °C the anatase-rutile transformation took place. Nanofibers with TiOxNy and added metals were also produced. Observations suggest that the increasing metal content led to the decrease of the nanofiber diameter. Electron microscopy revealed 2 nm platinum particles uniformly distributed. In the master's thesis, TiO2 and TiOxNy nanofibers with and without the addition of metals were successfully produced, which represents an excellent basis for further characterization of nanofibers for various purposes.