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Abstract: To increase the photocatalytic performance of Niobium(V) oxide (Nb2O5) it is necessary to increase its accessible surface area. The evaporation-induced self-assembly (EISA) synthesis method is well suited for the synthesis of mesoporous structures, but the optimisation of synthesis parameters for Nb2O5 is still limited. In this study, we demonstrate that the synthesis parameters — duration of evaporation, airflow rate, relative humidity and water content in the reaction mixture — significantly affect the specific surface area, mesoporous structure and photocatalytic performance of isopropanol oxidation into acetone of Nb2O5. Our results show that a combination of long evaporation duration, low airflow rate, low relative humidity and moderate water content are needed to obtain material with the highest specific surface area (145 m2 g−1) and a narrow hysteresis loop in the N2 sorption isotherm. This material exhibits four times higher photocatalytic activity compared to materials synthesised under less favourable conditions (14.3–17.7 μmol h−1 compared to 3.7 μmol h−1). We also show that the ordered mesoporous structure plays an important role in improving the photocatalytic performance: the materials with a higher degree of order exhibit about two times higher activity than the materials with a lower degree of order with the same specific surface area (10.4–12.1 μmol h−1 compared to 4.9–7.9 μmol h−1). These results provide valuable insights for optimising the synthesis of mesoporous niobium oxide to increase both the specific surface area and photocatalytic performance.
Keywords: Nb2O5, mesoporous material, evaporation-induced self-assembly, photocatalysis
Published in DiRROS: 12.01.2026; Views: 175; Downloads: 179
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Abstract: Atmospheric pressure plasma jet was employed to improve adhesion between polypropylene (PP) column wall and monolith used in chromatography. Different treatment conditions for modification of PP tube were used and the effects of treatment were analysed with X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Modified surfaces had higher oxygen content and surface was covered with small grain like structures. To explore effects of modification on adhesion between PP tube and monolith tensile strength measurements were conducted. It was shown that appropriate treatment conditions significantly increased bonding strength. The improvement of adhesion was attributed to increased oxygen functional groups obtained from plasma.
Published in DiRROS: 05.09.2025; Views: 405; Downloads: 194
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Abstract: Cigarette filters comprise plasticised cellulose acetate, a synthetic polymer categorized as bioplastic. They represent a significant source of microplastics (MPs), in particular microfibers, and associated chemicals, yet their impact on organisms, especially soil invertebrates, is not well-studied. This research examines the effects of MPs milled from smoked (SCF-MPs) and unsmoked cigarette filters (UCF-MPs) on terrestrial invertebrates (Porcellio scaber, Tenebrio molitor) and aquatic invertebrates (Daphnia magna, Brachionus calyciflorus). SCF-MPs and UCF-MPs were found to be 9.06 ± 4.1 μm and 12.71 ± 6.82 μm in size, respectively. Both samples contained triacetin and potentially toxic metals, while SCF-MPs also contained nicotine and a larger number of trace organic compounds. While exposure to SCF-MPs or UCF-MPs (up to 1.5 % MPs, w/w in soil) did not affect the survival of either terrestrial invertebrate, several physiological responses were observed. These included changes in immune parameters, energy-related biomarker levels, and altered glutathione S-transferase and acetylcholinesterase activities. Both types of MPs were acutely toxic to aquatic invertebrates, reducing the survival rates of B. calyciflorus (10 mg L−1 of either particle after 48h exposure) and D. magna (100 mg L−1 of SCF-MPs after 48h exposure). SCF-MPs generally caused more pronounced effects than UCF-MPs. This study highlights the need for effective environmental management to address both smoked and unsmoked cigarette filters.
Keywords: cigarette buts, cigarette filters, microfibers, crustaceans, insects, rotifers
Published in DiRROS: 09.05.2025; Views: 729; Downloads: 487
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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: 910; Downloads: 609
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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: 1014; Downloads: 2034
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