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1893. Evolution of surface functional groups and aromatic ring degradation upon treatment of polystyrene with hydroxyl radicalsAlenka Vesel, Rok Zaplotnik, Gregor Primc, Miran Mozetič, 2023, original scientific article Abstract: The surface properties of hydrocarbon polymers are inadequate for numerous applications. Hence, they require alteration via functionalisation with desired functional groups. Hydroxyl groups are often preferred, since they enable appropriate polarity for the irreversible grafting of desired molecules. In this study, the surface kinetics resulting from the treatment of polystyrene with hydroxyl (OH) radicals from the gas phase was fundamentally investigated through a precisely-designed experiment. Polystyrene samples were exposed to various known fluences of OH radicals, and the evolution of surface functional groups versus the OH fluence was monitored using high-resolution X-ray photoelectron spectroscopy (XPS). The fluences of OH radicals varied between 1 × 1018 and 4 × 1023 m−2 in the process of finding a threshold fluence for the formation of specific groups. The surface concentration of carbonyl (C=O) groups could be measured using XPS at a fluence of approximately 5 × 1020 m−2. The C=O groups became measurable at a fluence of approximately 1.5 × 1021 m−2, and carboxyl (COOH)/ester groups at approximately 4 × 1021 m−2. As deduced from the XPS, a concentration of C=O groups at approximately 5 % occurred before the degradation of the aromatic ring. The formation of other oxygen-functional groups required opening of the aromatic ring. The results have been explained using a two-step process, considering available theories vis-a-vis initial stages in the functionalisation of PS with polar functional groups.
Keywords: polistiren, kinetika površinske funkcionalizacije, OH radikali, vpliv doze radikalov, časovni razvoj, polystyrene, surface functionalisation kinetics, OH radicals
Published in DiRROS: 09.11.2023; Views: 364; Downloads: 155
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1896. Delavnica projekta LIFE SySTEMiC za lovce, lovske načrtovalce in raziskovalce v dinarsko jelovo-bukovih gozdovih, Mašun in Leskova dolina, 12. in 13. 10. 2023 : poročiloBoris Rantaša, Kristina Sever, Andrej Breznikar, Tjaša Baloh, Natalija Dovč, Evgen Ostanek, Peter Krma, Anton Smrekar, Matija Stergar, Miha Marenče, Hojka Kraigher, 2023, other monographs and other completed works Keywords: gozdovi, genetska pestrost, nega gozda, obnova gozda, upravljanje s prostoživečimi živalmi, objedanje, gozdno mladje, ujme, podnebne spremembe
Published in DiRROS: 08.11.2023; Views: 436; Downloads: 136
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1897. Optimization method based on simplex for surface area improved photocatalytic performance of ▫$g-C_3N_4$▫Matevž Roškarič, Janez Zavašnik, Dániel Dániel Zámbó, Tomaž Kotnik, Sebastijan Kovačič, Gregor Žerjav, Albin Pintar, 2023, original scientific article Abstract: The main objective of the present study was to increase the specific surface area (SBET) of graphitic carbon nitride (g-C3N4) prepared from dicyandiamide by effectively modifying the synthesis procedure using the Simplex optimization method. A remarkable increase in SBET was achieved in only a few steps, with the highest value of 86 m2/g. Compared to the reference material, the improved photocatalyst exhibited enhanced and unique structural, textural, optical, and electronic properties, reflected in the improved ability of the photocatalyst to degrade a variety of organic pollutants dissolved in water. By performing scavenger and spin-trapping experiments, it was confirmed that the major reactive oxygen species formed under visible-light illumination of the enhanced photocatalyst were singlet oxygen (1O2) and superoxide anion radicals (O2–•) with a purposed formation mechanism. The enhanced formation of 1O2 enabled high activity and stability of the optimized materials as well as selective response to degradation of the pharmaceutical compounds studied. By using the simple and fast Simplex optimization algorithm to determine new synthesis parameters, we obtained an improved g-C3N4 that completely degrades bisphenol A under the conditions studied.
Published in DiRROS: 08.11.2023; Views: 324; Downloads: 158
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1899. Humidity sensing ceria thin-filmsVilko Mandić, Arijeta Bafti, Luka Pavić, Ivana Panžić, Stanislav Kurajica, Jakov-Stjepan Pavelić, Zhen Shi, Katarina Mužina, Ivana Katarina Ivković, 2022, original scientific article Published in DiRROS: 07.11.2023; Views: 303; Downloads: 148
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