Synthesis and characterization of oxide-based thin films for photocatalytic application

Nourelhouda, Mokrani (2025) Synthesis and characterization of oxide-based thin films for photocatalytic application. Doctoral thesis, Faculté des Sciences et de la technologie.

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Abstract

The development of Sr-doped ZnO thin films using the Successive Ionic Layer Adsorption and Reaction (SILAR) method represents a significant step forward in advancing photocatalytic materials for environmental remediation. This study systematically investigates the effects of varying Sr concentrations (1, 3, 5, and 7 wt.%) on the structural, optical, and photocatalytic properties of ZnO thin films. X-ray diffraction analysis confirmed the polycrystalline nature of the films; with an observed increase in crystallite size along the (100) plane as Sr doping concentration increased. Notably, films with 5 wt.% Sr displayed exceptional photocatalytic efficiency under natural sunlight, achieving methylene blue degradation rates of up to 94.82% over three cycles, demonstrating remarkable stability and reusability. The photocatalytic activity of these films extended to the degradation of rose bengal and was particularly effective under basic pH conditions, with a maximum degradation rate of 97.60% achieved by films containing 40 wt.% Sr. Optical studies revealed that Sr doping led to a linear increase in the bandgap energy, enhancing the films' light absorption and electron-hole pair generation. Additionally, the integration of chemical additives, including ethylene glycol (EG), polyethylene glycol (PEG), ethylenediaminetetraacetic acid (EDTA), ethanolamine (EA), sodium dodecyl sulfate (SDS), and butynediol (BD), was explored to further tailor the films' properties. These additives influenced the films’ morphology, hydrophilicity, and photocatalytic performance, with EA-incorporated films achieving 92.53% degradation of methylene blue and EDTA-modified films showing a notable 23.68% degradation of amoxicillin. The research also highlighted the interplay between doping and additives in modulating structural and optical characteristics. While Sr doping enhanced crystallinity and photocatalytic activity, certain additives reduced the bandgap energy and improved hydrophilicity, critical for pollutant adsorption and photocatalysis. Furthermore, this study emphasizes the potential of Sr-doped ZnO thin films for diverse environmental applications, particularly in water purification and wastewater treatment. Future work could explore the integration of these films with heterojunctions or advanced nanostructures to further optimize their performance.

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