1. Effect of Ce:Ti ratio and cerium salts on the properties of mesoporous Ti-Ce oxides and their photocatalytic activityPeter Nadrah, Mateja Knap, T. Vikram Sagar, Andrijana Sever Škapin, Urška Lavrenčič Štangar, 2025, original scientific article Abstract: To investigate the influence of different CeO2 precursors and Ce:Ti ratios, we have synthesised 8 mesoporous Ti-Ce oxides via the evaporation-induced self-assembly (EISA) method with Ce:Ti ratios between 0.2 and 20 mol%.The materials exhibited type IV isotherms and a specific surface area of 140–180 m2⋅g 1 with pore diameters in range of 3–20 nm. The crystalline phases of materials comprised predominantly anatase with a significant decrease in overall crystalline content with increasing Ce:Ti ratio. Materials with higher Ce:Ti ratio showed an increased light absorption in the visible region. Although crystalline CeO2 was not detected, the presence of Ce(IV) was confirmed by X-ray photoelectron spectroscopy. For the photocatalytic experiments, we compared these materials with the TiO2-CeO2 composites of our previously published syntheses to yield 16 samples synthesized via three synthesis approaches: (1) concurrent synthesis from titanium alkoxide and cerium salts in one pot, (2) synthesis of TiO2 in the presence of previously-synthesised CeO2 and (3) physical mixing of separately-synthesised TiO2 and CeO2. Samples produced by physically mixing the separately-synthesised TiO2 and CeO2 showed the best photocatalytic activity towards gaseous isopropanol degradation, while the samples with TiO2 synthesised in the presence of CeO2 showed the best photocatalytic stability. Keywords: Ti-Ce oxides, evaporation-induced self-assembly, isopropanol oxidation, photocatalysis, mesoporous material Published in DiRROS: 30.01.2025; Views: 99; Downloads: 81
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2. Fotokatalitski heterostrukturirani nanomateriali za izkoriščanje sončne energije : zaključno poročilo o rezultatih raziskovalnega projektaAndrijana Sever Škapin, Peter Nadrah, Miran Gaberšček, 2024, final research report Keywords: fotokataliza, heterostrukture, TiO2-CeO2, TiO2-Cu, sokatalizator, photocatalysis, heterostructures, co-catalyst Published in DiRROS: 14.10.2024; Views: 418; Downloads: 0 This document has many files! More... |
3. Comparing the effects of pristine and UV–VIS aged microplastics : behavioural response of model terrestrial and freshwater crustaceansPrimož Zidar, Dana Kühnel, Andrijana Sever Škapin, Tina Skalar, Damjana Drobne, Luka Škrlep, Branka Mušič, Anita Jemec Kokalj, 2024, original scientific article Abstract: Physico-chemical properties of microplastics (MPs) change during weathering in the environment. There is a lack of knowledge about the effects of such environmentally relevant MPs on organisms. We investigated: 1) the physico-chemical changes of MPs due to UV–VIS weathering, and 2) compared the effect of pristine and aged MPs on the behaviour of the water flea Daphnia magna and terrestrial crustacean Porcellio scaber. Dry powders of MPs were produced from widely used polymer types: disposable three-layer polypropylene (PP) medical masks (inner, middle and outer), polyester textile fibres, car tires and low-density polyethylene (LDPE) bags and were subjected to accelerated ultraviolet–visible (UV–VIS) ageing. Our results show that the extent of transformation depends on the type of polymer, with PP showing the most changes, followed by LDPE, textile fibres and tire particles. Obvious fragmentation was observed in PP and textile fibres. In the case of PP, but not polyester textile fibres, changes in FTIR spectra and surface properties were observed. Tire particles and LDPE did not change in size, but clear changes were observed in their FTIR spectra. Most MPs, aged and pristine, did not affect the swimming of daphnids. The only effect observed was a significant increase in path length and swimming speed for the pristine tire particles when the recording was done with particles remaining in the wells. After transfer to a clean medium, this effect was no longer present, suggesting a physical rather than chemical effect. Similarly, woodlice showed no significant avoidance response to the MPs tested, although there was a noticeable trend to avoid soils contaminated with pristine polyester textile fibers and preference towards the soils contaminated with aged MP of the middle mask layer. Overall, the apparent changes in physico-chemical properties of MPs after accelerated ageing were not reflected in their effects on woodlice and daphnids. Keywords: Daphnia magna, Porcellio scaber, polyethylene, polypropylene, weathering, FTIR Published in DiRROS: 08.10.2024; Views: 312; Downloads: 1506
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4. Tailoring the crystalline and amorphous phase ratios of TiO2 through the use of organic additives during hydrothermal synthesisNejc Rozman, Andrijana Sever Škapin, David Maria Tobaldi, Goran Dražić, Peter Nadrah, 2024, original scientific article Abstract: The photocatalytic properties of TiO2 are primarily determined by its crystallinity and crystalline phase ratios. To improve the photocatalytic properties of TiO2, greater control over the formation of crystalline and amorphous phases during synthesis is therefore required. In this study, we demonstrate how the addition of minute amounts of three organic compounds (isopropanol, acetone and acetic acid) during hydrothermal treatment affects the amorphous and crystalline phase ratios: the addition of isopropanol or acetone accelerates the phase transition from anatase and brookite to rutile, whereas the addition of acetic acid inhibits the transformation of anatase to rutile, increasing the content of amorphous phase compared to samples where no organic compound was added. We show that the combination of the organic compound added, along with the duration of the hydrothermal treatment, can be used to tailor the phase composition of TiO2, so as to obtain either: i) TiO2 with a high content of both rutile and amorphous phase, ii) TiO2 with a high rutile content and iii) TiO2 with different ratios of all four phases, when the duration of synthesis is short (2–4 h). The materials synthesized exhibited high photocatalytic activity (in most cases higher than P25), which is attributed to the beneficial phase composition and high specific surface area. Keywords: sol-gel processes, X-ray methods, chemical properties, TiO2, photocatalysis Published in DiRROS: 14.08.2024; Views: 413; Downloads: 372
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5. Lastnosti lesa iz rudnika SitarjevecMiha Humar, Boštjan Lesar, Davor Kržišnik, Andreja Pondelak, Andrijana Sever Škapin, Angela Balzano, José Gonçalves, 2024, original scientific article Abstract: Rudarska tradicija v Litiji, segajoča v staro železno dobo, je vključevala intenzivno uporabo lesa v rudnikih, še posebej za podporo in zaščito rovov. Rudnik Sitarjevec je bil znova odprt za turizem leta 2017, in v letu 2021 so odprli glavni rov. Les ostaja ključen material v rudnikih, čeprav so ga v preteklosti nadomeščali z drugimi materiali. Uporabljeni les je izpostavljen razkroju zaradi visoke vlažnosti in gliv, kot je bela hišna goba. Ta gliva lahko povzroči razgradnjo lesa in je pogosta v vlažnih okoljih rudnikov. Obstoj gliv je pomemben, saj lahko vplivajo na obiskovalce rudnika. Visoka relativna zračna vlažnost (96,6 %) in stalna temperatura (10,1 °C) v rudniku ustvarjata razmere, ki so ugodne za rast gliv, vendar pa relativno nizka temperatura ni omejujoč dejavnik za razgradnjo lesa. Koncentracija glivnih spor v rudniku je visoka in je razložena z razširjenostjo gliv v samem rudniku. Poleg tega smo opazili, da je v lesu veliko anorganskih onesnaževal ter veliko kristalov. Keywords: razkroj, bela hišna goba, težke kovine, kristali, spore Published in DiRROS: 22.07.2024; Views: 432; Downloads: 189
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6. Lastnosti lesa iz rudnika SitarjevecMiha Humar, Boštjan Lesar, Davor Kržišnik, Andreja Pondelak, Andrijana Sever Škapin, Angela Balzano, José Gonçalves, 2024, original scientific article Abstract: Rudarska tradicija v Litiji, segajoča v staro železno dobo, je vključevala intenzivno uporabo lesa v rudnikih, še posebej za podporo in zaščito rovov. Rudnik Sitarjevec je bil znova odprt za turizem leta 2017, in v letu 2021 so odprli glavni rov. Les ostaja ključen material v rudnikih, čeprav so ga v preteklosti nadomeščali z drugimi materiali. Uporabljeni les je izpostavljen razkroju zaradi visoke vlažnosti in gliv, kot je bela hišna goba. Ta gliva lahko povzroči razgradnjo lesa in je pogosta v vlažnih okoljih rudnikov. Obstoj gliv je pomemben, saj lahko vplivajo na obiskovalce rudnika. Visoka relativna zračna vlažnost (96,6 %) in stalna temperatura (10,1 °C) v rudniku ustvarjata razmere, ki so ugodne za rast gliv, vendar pa relativno nizka temperatura ni omejujoč dejavnik za razgradnjo lesa. Koncentracija glivnih spor v rudniku je visoka in je razložena z razširjenostjo gliv v samem rudniku. Poleg tega smo opazili, da je v lesu veliko anorganskih onesnaževal ter veliko kristalov. Keywords: razkroj, bela hišna goba, težke kovine, kristali, spore Published in DiRROS: 21.06.2024; Views: 883; Downloads: 256
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7. Biocompatible polyelectrolyte multilayers with copper oxide and zinc oxide nanoparticles for inhibiting bacterial growthNives Matijaković Mlinarić, Stefanie Altenried, Atiđa Selmani, Juraj Nikolić, Aleksander Učakar, Anamarija Zore, Anže Abram, Sandro Lehner, Andrijana Sever Škapin, Monika Kušter, Eva Roblegg, Davor Kovačević, Qun Ren, Klemen Bohinc, 2024, original scientific article Abstract: The prevalence of bacterial infections presents a significant challenge in the medical field, demanding effective strategies to impede bacterial adhesion and growth on various surfaces. The conducted study investigates the efficacy of polyelectrolyte multilayers─comprising poly(allylamine hydrochloride) (PAH) and alginate (ALG)─embedded with zinc oxide (ZnO) and copper oxide (CuO) nanoparticles (NPs) to inhibit bacterial adhesion on stainless-steel surfaces. Surface characterization involved zeta potential, contact angle, and roughness assessments. The effect of NP composition, size, and morphology in conjunction with polycation or polyanion terminating multilayers was evaluated against planktonic and surface-adhered Escherichia coli (E. coli) cells. Surfaces with the positively charged PAH-terminating multilayer displayed higher water contact angles (≈ 63°) than the negatively charged ALG-terminating multilayers (≈ 45°). Multilayers containing ZnO NPs showed a significant inhibition of planktonic E. coli growth, >99%. Moreover, complete growth inhibition of surface-adhered E. coli was achieved for multilayers containing both ZnO and CuO. Due to their larger specific surface area, rod-like ZnO NPs displayed higher antibacterial activity. The samples with ALG as the terminating layer showed more substantial antibacterial properties than samples with PAH as the terminating layer. Biocompatibility tests on immortalized human keratinocyte cells revealed good compatibility with multilayers incorporating NPs. In summary, this study underscores the potential of ZnO and CuO NPs within PAH/ALG multilayers for antibacterial applications without compromising their cytocompatibility. Keywords: polyelectrolyte multilayers, alginate, poly(allylamine hydrochloride), CuO, ZnO, nanoparticles, Escherichia coli Published in DiRROS: 06.06.2024; Views: 528; Downloads: 419
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8. Diketopyrrolopyrrole pigment core@multi-layer ▫$SiO_2$▫ shell with improved photochemical stabilityErika Švara Fabjan, Zineb Saghi, Paul A. Midgley, Mojca Otoničar, Goran Dražić, Miran Gaberšček, Andrijana Sever Škapin, 2018, original scientific article Abstract: A model organic pigment (diketopyrrolopyrrole) is encapsulated by a silica coating in order to improve its photochemical stability. Unlike in previous works where single-layer silica coatings were used for similar purposes, we here propose creation of a multi-layer silica shell synthesized via in-situ sol-gel method, which should significantly improve the homogeneity and thus the protection ability of the coating. This is done by repeating the basic two-step process (pigment surface modification and silica encapsulation) several times, creating the final protective shell in a layer-by-layer fashion. The compositional and structural properties of the prepared coatings is studied using Fourier-transform infrared spectroscopy, differential thermal and thermogravimetric analysis, nitrogen adsorption measurements and transmission electron microscopy. Photochemical stability of non-encapsulated and encapsulated pigment particles is evaluated via the so-called fast-irradiation method. Various correlations between the essential coating properties, such as thickness, porosity, SiO2 content, and the corresponding photochemical stability of the samples are established and discussed in detail. As a whole, our results confirm the basic hypothesis, that multiple-layered silica shells show improved pigment protection ability in comparison to the single-layer coatings. Keywords: organic pigments, silica coating, encapsulation, morphology, photocemical stability Published in DiRROS: 27.03.2024; Views: 868; Downloads: 347
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9. Weathering effects on cellulose acetate microplastics from discarded cigarette buttsBranka Mušič, Andrijana Sever Škapin, 2024, published scientific conference contribution (invited lecture) Abstract: Cellulose acetate, commonly used in cigarette filters, poses environmental concerns due to its questionable (bio)degradability and prevalent presence in nature. This study compares the weathering effects on two types of cigarette filters: traditional and newer filters used in heated tobacco devices (HTP). Microplastics were derived from used cigarette parts and then subjected to artificial aging. Analytical techniques (Thermogravimetry-Differential Scanning Calorimetry TG/DSC, Fourier-Transform Infrared Spectroscopic Analysis (FTIR)) and loose bulk density measurements were employed pre- and post-aging cellulose acetate of both types of samples. Despite increasing evidence influencing European Union (EU) directives on tobacco product disposal, there's a lack of systematic analysis on the weathering impact, especially concerning the touted environmental benefits of newer filters. Results indicate decreased particle size in cellulose acetate filters post-aging. Variances were observed in thermal behavior, yet FTIR spectra remained unchanged. Keywords: cellulose acetate, cigarette filters, microplastics, artificial weathering, polymer degradation Published in DiRROS: 12.03.2024; Views: 854; Downloads: 619
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