1. Antibacterial effect of polymethyl methacrylate resin base containing TiO2 nanoparticlesAnamarija Zore, Anže Abram, Aleksander Učakar, Ivo Godina, Franc Rojko, Roman Štukelj, Andrijana Sever Škapin, Rajko Vidrih, Olivera Dolić, Valentina Veselinović, Klemen Bohinc, 2022, original scientific article Abstract: Restorations in dentistry must reproduce the aspect of the patient’s natural teeth and require non-toxicity, biocompatibility, and good mechanical properties in order to last longer. Restorations are permanently in contact with microbes that can adhere to and form biofilms. The purpose of this study was to determine the adhesion extent of Streptococcus mutans to polymethyl methacrylate (PMMA) resin base containing TiO2 nanoparticles. To understand the adhesion of Streptococcus mutans on the modified resin-based surfaces, the following surface properties were measured: the roughness, contact angle, zeta potential and CIE color parameters. Evaluation of tensile stress performance in TiO2 modified PMMA showed that the maximum tensile stress of the modified PMMA resin decreases with an increasing amount of TiO2 nanoparticles. The increasing amount of TiO2 decreases the roughness and causes contact angles in the border between hydrophilic and hydrophobic surfaces. All the studied surfaces are negatively charged and added TiO2 tends to increase the zeta potential. The addition of TiO2 nanoparticles increases the lightness and decreases the intensity of the red and yellow color. The increasing addition of TiO2 nanoparticles into PMMA increases the morphological change of bacterial cells.
Keywords: bacterial adhesion, Streptococcus mutans, polymethyl methacrylate resin, TiO2, surface properties
Published in DiRROS: 20.12.2023; Views: 166; Downloads: 84
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2. Hydrothermal synthesis of rare-earth modified titania : influence on phase composition, optical properties, and photocatalytic activityNejc Rozman, David Maria Tobaldi, Uroš Cvelbar, Harinarayanan Puliyalil, Joao Antonio Labrincha, Andraž Legat, Andrijana Sever Škapin, 2019, original scientific article Abstract: In order to expand the use of titania indoor as well as to increase its overall performance, narrowing the band gap is one of the possibilities to achieve this. Modifying with rare earths (REs) has been relatively unexplored, especially the modification of rutile with rare earth cations. The aim of this study was to find the influence of the modification of TiO2 with rare earths on its structural, optical, morphological, and photocatalytic properties. Titania was synthesized using TiOSO4 as the source of titanium via hydrothermal synthesis procedure at low temperature (200 °C) and modified with selected rare earth elements, namely, Ce, La, and Gd. Structural properties of samples were determined by X-ray powder diffraction (XRD), and the phase ratio was calculated using the Rietveld method. Optical properties were analyzed by ultraviolet and visible light (UV-Vis) spectroscopy. Field emission scanning electron microscope (FE-SEM) was used to determine the morphological properties of samples and to estimate the size of primary crystals. X-ray photoelectron spectroscopy (XPS) was used to determine the chemical bonding properties of samples. Photocatalytic activity of the prepared photocatalysts as well as the titania available on the market (P25) was measured in three different setups, assessing volatile organic compound (VOC) degradation, NOx abatement, and water purification. It was found out that modification with rare earth elements slows down the transformation of anatase and brookite to rutile. Whereas the unmodified sample was composed of only rutile, La- and Gd-modified samples contained anatase and rutile, and Ce-modified samples consisted of anatase, brookite, and rutile. Modification with rare earth metals has turned out to be detrimental to photocatalytic activity. In all cases, pure TiO2 outperformed the modified samples. Cerium-modified TiO2 was the least active sample, despite having a light absorption tail up to 585 nm wavelength. La- and Gd-modified samples did not show a significant shift in light absorption when compared to the pure TiO2 sample. The reason for the lower activity of modified samples was attributed to a greater Ti3+/Ti4+ ratio and a large amount of hydroxyl oxygen found in pure TiO2. All the modified samples had a smaller Ti3+/Ti4+ ratio and less hydroxyl oxygen
Keywords: TiO2, photocatalytic activity, rare earths, modification, visible light activity
Published in DiRROS: 22.11.2023; Views: 264; Downloads: 139
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3. Photocatalytic CO2 reduction over mesoporous TiO2 photocatalystsMartin Reli, Peter Nadrah, Miroslava Filip Edelmannová, Rudolf Ricka, Andrijana Sever Škapin, Urška Lavrenčič Štangar, Kamila Kočí, 2024, original scientific article Abstract: In this study, we investigated different synthesis methods (template-free and template-based) using copolymers of poly(ethylene oxide) and poly(propylene oxide) to enhance the CO2 reduction activity of mesoporous TiO2. Our main goal was to identify key factors affecting photocatalyst efficiency and selectivity. We compared the newly synthesized TiO2 photocatalysts with the commercial photocatalyst P25. Among the materials studied, TiO2-P123 in its pure anatase form demonstrated the highest photoreduction efficiency and CO2 selectivity. In contrast, TiO2-EG, TiO2-F127, and P25, which contained both rutile and anatase phases, exhibited decreased photoactivity due to the formation of a type II heterojunction between the phases and higher oxygen adsorption on rutile's surface. Additionally, we observed that the choice of chemicals for photocatalyst preparation significantly influenced the specific surface area. TiO2-P123, the most active photocatalyst, had the highest specific surface area, providing more reactive sites for improved light absorption efficiency and prolonged electron-hole pair lifetimes, resulting in enhanced photocatalytic activity. We also calculated apparent quantum yields to support our findings.
Keywords: CO2 reduction, TiO2, photocatalysis, mesoporous material, Sol-gel method
Published in DiRROS: 14.11.2023; Views: 352; Downloads: 36
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