Due to their large specific surface area, chemical stability, and photocatalytic activity, titanium dioxide (TiO$_2$) nanostructures play an important role in applications such as energy conversion, environmental remediation, construction materials, and biomedicine. TiO$_2$ occurs in several polymorphic forms, of which anatase and rutile are the most widely studied, with rutile being the thermodynamically most stable phase. The formation and final properties of TiO$_2$ nanostructures are strongly influenced by nucleation, crystal growth, and synthesis conditions.
In this master’s thesis, we synthesized a water-soluble titanium complex that was used as a precursor for the hydrothermal synthesis of TiO$_2$. The concentration of the precursor solution was determined using UV–Vis spectroscopy. Hydrothermal synthesis was performed in an autoclave at different precursor concentrations in order to investigate their effect on the size, number, and morphology of the resulting nanocrystals. The obtained nanostructures were evaluated using SEM analysis, and a calibration curve as well as the mass balance of the process were established. The analyses showed that under the selected reaction conditions, primarily rutile nanorods were formed, with higher precursor concentrations leading to the formation of a larger number of nanocrystals.
We also investigated crystallization on different substrates, studying the heterogeneous nucleation of TiO$_2$ on sapphire glass, conductive FTO and ITO glasses with different roughness and conductivity, and on a polyHIPE substrate constructed from TiO$_2$ nanoparticles. The aim was to evaluate how the surface properties of substrates influence the morphology and size of the resulting crystals. A larger number of rutile nanocrystals was observed on conductive glass substrates, whereas nucleation on inert sapphire glass was significantly reduced. The presence of the substrate also affected crystals formed in solution, which were smaller compared to those in the control sample.
Finally, we examined the photocatalytic activity of the synthesized TiO$_2$ nanostructures in the degradation of the pollutant bisphenol A (BPA) and compared their performance to commercial TiO$_2$. The purpose was to confirm the photocatalytic activity of the synthesized nanocrystals despite the predominance of the rutile phase, which is generally considered less photocatalytically active compared to other TiO$_2$ polymorphs.
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