[EN] Thin film technology plays an important role in our day-to-day life. This technology involves the application of thin layers of materials, often at the micron or nanometer scale, onto different substrates. Thin films can alter the properties of these substrates and impart certain functionality. In recent years, coatings with multifunctionality through surface functionalization concepts have attracted significant interest in the glass industry. This is mainly due to their numerous applications, such as in solar cells, smart windows, and photocatalysis. In this research, the sol-gel method is used to obtain coatings with different functionalities such as antireflective, hydrophobic, photocatalytic, antibacterial and electrochromic properties. The sol-gel method is preferred over other deposition techniques such as pulsed laser deposition, chemical vapor deposition, and magnetron sputtering since it yields high-quality coatings at a low-cost and with a simple deposition procedure. In the scope of this research, coatings consisting of silica-titania (SiO2-TiO2) and triethoxy(octyl)silane (OTES)-modified SiO2 sol were deposited onto glass substrates to achieve antireflective and hydrophobic functionalities. On the other hand, zinc oxide (ZnO) and silver nanoparticle (AgNP) doped ZnO thin film were used to obtain photocatalytic and antibacterial properties. In addition, the ZnO thin film deposited on fluorine-doped tin oxide (FTO) glass was utilized as a counter electrode in a tungsten trioxide (WO3)-based electrochromic device. Thus, this research work is divided into three main parts based on the functionalities of the coating. In the first part of the research work, a double-layer coating was designed and fabricated on glass surfaces by sol-gel method using a silica-titania (SiO2-TiO2) thin film as the bottom layer and an inorganic-organic octyl triethoxy silane (OTES) modified SiO2 upper layer. The refractive index of the SiO2-TiO2 and OTES-modified SiO2 layers were 1.79 and 1.45, and their thicknesses were approximately 76.8 nm and 94.2 nm, respectively. A uniform and crack-free SiO2/SiO2-TiO2 coating was obtained with a percentage transmission of 99.1 in the visible region of the solar spectrum at 550 nm wavelength and with good hydrophobicity (contact angle of 104º). The developed multilayer coating can function as an antireflective and self-cleaning coating as cover glass on top of solar cells. In the second part, ZnO thin films on glass substrates were prepared via sol-gel by dip-coating technique to use them as photocatalyst. The effect of annealing temperature (300-550 ºC) of the ZnO thin film in the degradation of organic methyl orange (MO) dye using a solar simulator was evaluated. The photocatalytic properties of the ZnO films were also analyzed as a function of the optical, morphology, and compositional properties. XRD and Raman analysis confirmed the hexagonal wurtzite structure of ZnO. On the other hand, homogeneous, crack-free, and spherical-like features of ZnO films were observed from the SEM micrograph. The percentage transmission of all ZnO films annealed at different temperatures was > 80% in the 400–800 nm wavelength range. The best photocatalytic activity under solar radiation was shown by ZnO thin film annealed at 450 ºC. ZnO films developed can accelerate the degradation of MO, one of the main water pollutants found in the effluent from the textile and paper sectors. Furthermore, silver nanoparticles (AgNPs) were also incorporated into the ZnO film to evaluate their effect on the photocatalytic performance and their potential use as antibacterial coating. As-prepared AgNPs have been incorporated into ZnO sols to produce AgNP-doped ZnO sol (Ag-ZnO) and Ag-ZnO coatings were developed using simple sol-gel dip coating. The photocatalytic activity was studied through the degradation of methyl orange in aqueous solution under solar simulator. A significant improvement of the photocatalytic activity was observed for the Ag-ZnO coatings compared to coatings without Ag. The coating using 3 mol% AgNP in ZnO showed the best photocatalytic activity. This effect can be attributed to the role of silver in enhancing the efficiency of superoxide anion radical and hydroxyl radical generation. Antibacterial application of ZnO and AgNP doped ZnO thin films using Escherichia coli (E.coli) as a model for gram-negative bacteria, and Staphylococcus aureus (S. aureus) as gram-positive bacteria was also studied. AgNP-doped ZnO exhibited superior antibacterial activity relative to undoped ZnO thin films. Finally, in the third part, the fabrication of electrochromic devices using sol-gel-derived metal oxide thin films was used. Electrochromic devices (ECD) have attracted significant interest in the past two years for their potential uses in a wide variety of applications such as optical displays, anti-glare automobile rear-view mirrors, and smart windows. However, challenges such as simple and cost-effective electrochromic material preparation, insufficient coloration, lengthy switching times, and poor cycling stability still need to be overcome. In the thesis, an electrochromic device is fabricated by combining WO3 thin film as a working electrode and a ZnO thin film as a counter electrode on FTO glass substrates by a simple sol-gel spin coating method. Graphite-coated FTO (C-based ECD) was also used as a counter electrode for a comparative analysis of the ECDs. X-ray diffraction (XRD) studies showed that WO3 and ZnO films were well crystallized in monoclinic and hexagonal wurtzite structures with crystallite sizes of 38.5 and 42.2 nm, respectively. Field emission scanning electron microscopy (FE-SEM) images confirmed the formation of porous and nanorod-like structures for WO3 and ZnO films, respectively. Furthermore, the research results showed that the optical contrast at 600 nm of WO3-ZnO ECD was almost twice that of the WO3-C-based ECD. Cyclic voltammetry and chronoamperometry measurements were also used to study the electrochromic properties of the films.

I am grateful to the European Union's Horizon 2020 research and innovation programme (grant agreement No. 739566), as well as projects VEGA 1/0844/21 and VEGA 1/0431/18 of the Grant Agency of Slovak Republic. Additionally, I thank the Journal of the European Ceramic Society (JECS) Trust for funding my mobility projects at CSIC-ICV

Tesis Doctoral inédita cotutelada por la Trenčianska Univerzita Alexandra Dubčeka V Trenčíne (Eslovaquia) y por la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química Inorgánica. Fecha de Lectura: 16-12-2024

Peer reviewed