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

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 EgI = 4.485 eV and EgII = 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.

Technological challenges in the development of silica-titania platform for integrated optics

“…Scaling up the sol-gel process and dip-coating method for large-scale production can be challenging [12]. Achieving consistent film quality and uniformity across larger areas can be difficult, and the process may require substantial optimization to guarantee reproducibility [13]. The sol-gel process and dip-coating method typically involve specialized equipment and precise process control.…”

Robust Biobased Membrane: Self-Entangled Cellulose Nanofibrils–ZnO–Ag Composite with High Photocatalytic Performance for Efficient Dye-Contaminated Water Treatment

“…The tensile strength of the wet membrane was measured by using a tensile tester (STB-1225S, AND, Japan) equipped with a 2. 5 span was set at 25 mm. Before testing, the water on the specimen surface was carefully wiped out using a filter paper.…”

“…These ROS then degrade organic compounds such as dyes in contaminated water. ZnO is a well-known photocatalyst candidate for photodegrading dye-contaminated water − due to its high activity, strong oxidation ability, low cost, and nontoxic features . However, the pure form of ZnO exhibits slow photodegradation due to the high recombination rate of charge carriers within the material. , To address this issue, silver nanoparticles (AgNPs) have been employed as a support for ZnO, leading to a significant enhancement in the photocatalytic efficiency of ZnO.…”

Sol–Gel Technology Applied to Materials Science: Synthesis, Characterization and Applications

“…Wojtasik et al [8] fabricated photocatalytically active ZnO coatings on soda lime glass substrates using the sol-gel method and the dip-coating technique. Their study aimed to determine the effect of the duration of the sol aging process on the properties of the fabricated ZnO films.…”