Zinc Oxide Films Fabricated via Sol-Gel Method and Dip-Coating Technique-Effect of Sol Aging on Optical Properties, Morphology and Photocatalytic Activity

Katarzyna Wojtasik; Magdalena Zięba; Cuma Tyszkiewicz; Wojciech Pakieła; Grażyna Żak; Olgierd Jeremiasz; Ewa Gondek; Kazimierz Drabczyk; Paweł Karasiński

doi:10.3390/ma16051898

Zinc Oxide Films Fabricated via Sol-Gel Method and Dip-Coating Technique-Effect of Sol Aging on Optical Properties, Morphology and Photocatalytic Activity

Materials (Basel). 2023 Feb 24;16(5):1898. doi: 10.3390/ma16051898.

Authors

Katarzyna Wojtasik¹, Magdalena Zięba¹, Cuma Tyszkiewicz¹, Wojciech Pakieła², Grażyna Żak³, Olgierd Jeremiasz^{4

5}, Ewa Gondek⁶, Kazimierz Drabczyk⁴, Paweł Karasiński¹

Affiliations

¹ Department of Optoelectronics, Silesian University of Technology, B. Krzywoustego 2, 44-100 Gliwice, Poland.
² Department of Engineering Materials and Biomaterials, Silesian University of Technology, Konarskiego 18a, 44-100 Gliwice, Poland.
³ Oil and Gas Institute-National Research Institute, Lubicz 25A, 31-503 Kraków, Poland.
⁴ Institute of Metallurgy and Materials Science, Polish Academy of Sciences, Reymonta 25, 30-059 Kraków, Poland.
⁵ Helioenergia Sp. z o.o., Rybnicka 68, 44-238 Czerwionka-Leszczyny, Poland.
⁶ Department of Physics, Cracow University of Technology, Podchorążych 1, 31-084 Kraków, Poland.

Abstract

Zinc oxide layers on soda-lime glass substrates were fabricated using the sol-gel method and the dip-coating technique. Zinc acetate dihydrate was applied as the precursor, while diethanolamine as the stabilizing agent. This study aimed to determine what effect has the duration of the sol aging process on the properties of fabricated ZnO films. Investigations were carried out with the sol that was aged during the period from 2 to 64 days. The sol was studied using the dynamic light scattering method to determine its distribution of molecule size. The properties of ZnO layers were studied using the following methods: scanning electron microscopy, atomic force microscopy, transmission and reflection spectroscopy in the UV-Vis range, and the goniometric method for determination of the water contact angle. Furthermore, photocatalytic properties of ZnO layers were studied by the observation and quantification of the methylene blue dye degradation in an aqueous solution under UV illumination. Our studies showed that ZnO layers have grain structure, and their physical-chemical properties depend on the duration of aging. The strongest photocatalytic activity was observed for layers produced from the sol that was aged over 30 days. These layers have also the greatest porosity (37.1%) and the largest water contact angle (68.53°). Our studies have also shown that there are two absorption bands in studied ZnO layers, and values of optical energy band gaps determined from positions of maxima in reflectance characteristics are equal to those determined using the Tauc method. Optical energy band gaps of the ZnO layer fabricated from the sol aged over 30 days are E_g^I = 4.485 eV and E_g^II = 3.300 eV for the first and second bands, respectively. This layer also showed the highest photocatalytic activity, causing the pollution to degrade 79.5% after 120 min of UV irradiation. We believe that ZnO layers presented here, thanks to their attractive photocatalytic properties, may find application in environmental protection for the degradation of organic pollutants.

Keywords: dip-coating; energy band gap; hydrophilicity; photocatalytic activity; sol-gel; thin layers; zinc oxide.

Abstract

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