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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: 321; Downloads: 337
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Published in DiRROS: 02.07.2025; Views: 724; Downloads: 434
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Published in DiRROS: 03.07.2023; Views: 2095; Downloads: 1241
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Abstract: Synthesis of zinc oxide (ZnO) nanoparticles (NPs) was mediated by plant extracts to assist in the reduction of zinc atoms during the synthesis and act as a capping agent during annealing.The preparation used ethanolic extracts from the roots of Japanese knotweed (Fallopia japonica). Two major outcomes could be made. (i)A synergistic effect of multiple polyphenolic components in the extract is needed to achieve the capping effect of crystallite growth during thermal annealing at 450 °C characterized by an exponential growth factor (n) of 4.4 compared to n = 3 for bare ZnO. (ii) Synergism between the ZnO NPs and plant extracts resulted in superior antimicrobial activity against both Gram-positive bacteria, e.g., Staphylococcus aureus, and Gram-negative bacteria, e.g., Escherichia coli and Campylobacter jejuni. The materials were also tested for their antimicrobial activity against S. aureus under ultraviolet (UV) illumination. Also here, the photocatalyst prepared with plant extracts was found to be superior. The residues of the plant extract molecules on the surface of the catalyst were identified as the main cause of the observed differences, as proved by thermal gravimetry. Such a preparation using ethanolic extract of Fallopia japonica could serve as a more controlled synthesis of ZnO and potentially other metal oxides, with low environmental impact and high abundance in nature.
Published in DiRROS: 21.11.2022; Views: 1509; Downloads: 876
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