Prema učinkovitoj fotodegradaciji mikroplastike: primjena tankih filmova cinkovog oksida dobivenih metodom plazmom potpomognute depozicije atomskih slojeva

This thesis presents a systematic study of zinc oxide (ZnO) thin films synthesised by plasmaenhanced atomic layer deposition (PEALD). The focus is on their structural, optical and photocatalytic properties as a function of the deposition conditions and their potential application in the degradation of microplastics. A comprehensive set of characterisation experimental techniques was used to analyse the films: grazing incidence X-ray diffraction (GIXRD), scanning and transmission electron microscopy (SEM, TEM), X-ray photoelectron spectroscopy (XPS), UV-Vis spectroscopy, secondary ion mass spectroscopy (SIMS) and photoluminescence spectroscopy (PL). Firstly, the influence of deposition temperature was investigated and it was found that films grown at lower temperatures, particularly at 60 C, exhibited higher photocatalytic activity. This improvement was attributed to a polycrystalline microstructure consisting of nanometresized grains (5 nm) with a high surface-to-volume ratio and a dense network of grain boundaries. These features promote the trapping of charge carriers at the surface and suppress recombination, thereby increasing the availability of active species for photocatalytic reactions. To enable deposition on thermally sensitive substrates, PEALD was also performed at room temperature with different radio frequency (RF) plasma powers. A strong dependence on the plasma power was observed. Films deposited with powers below 200 W are amorphous and showed a weak photocatalytic response, while those deposited at or above 200 W formed nanocrystalline structures with significantly improved photocatalytic activity. This shows that both the deposition temperature and the plasma power are crucial parameters for tuning the photoactive properties of ZnO films. Based on these findings, ZnO thin films were applied to poly(ethylene terephthalate) (PET) microfibres for its photocatalytic degradation. Two sets of parameters (80 C with 50 W and room temperature at 250 W) were found to be particularly effective in yielding thin ZnO films which initiate polymer degradation. A range of experimental conditions were investigated, including different water media (ultrapure water, tap water, water solutions), film thicknesses, light sources (UV and sun-simulated) and illumination durations. The best photocatalytic degradation was achieved in tap water and simulated seawater under 48 hours of UV exposure. Overall, thiswork demonstrates howfine-tuning ofPEALDparameters can lead to ZnO thin films with tailored photocatalytic performance and opens new directions for their use in addressing critical challenges in microplastic pollution and water treatment technologies.