| 1. |
- Bassani, Carlos L., et al.
(författare)
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Nanocrystal Assemblies : Current Advances and Open Problems
- 2024
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Ingår i: ACS Nano. - 1936-0851. ; 18:23, s. 14791-14840
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Forskningsöversikt (refereegranskat)abstract
- We explore the potential of nanocrystals (a term used equivalently to nanoparticles) as building blocks for nanomaterials, and the current advances and open challenges for fundamental science developments and applications. Nanocrystal assemblies are inherently multiscale, and the generation of revolutionary material properties requires a precise understanding of the relationship between structure and function, the former being determined by classical effects and the latter often by quantum effects. With an emphasis on theory and computation, we discuss challenges that hamper current assembly strategies and to what extent nanocrystal assemblies represent thermodynamic equilibrium or kinetically trapped metastable states. We also examine dynamic effects and optimization of assembly protocols. Finally, we discuss promising material functions and examples of their realization with nanocrystal assemblies.
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| 2. |
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| 3. |
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| 4. |
- Cunha, M. S., et al.
(författare)
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Rotation and pulsation in Ap stars : first light results from TESS sectors 1 and 2
- 2019
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Ingår i: Monthly notices of the Royal Astronomical Society. - : OXFORD UNIV PRESS. - 0035-8711 .- 1365-2966. ; 487:3, s. 3523-3549
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Tidskriftsartikel (refereegranskat)abstract
- We present the first results from the Transiting Exoplanet Survey Satellite (TESS) on the rotational and pulsational variability of magnetic chemically peculiar A-type stars. We analyse TESS 2-min cadence data from sectors 1 and 2 on a sample of 83 stars. Five new rapidly oscillating Ap (roAp) stars are announced. One of these pulsates with periods around 4.7 min, making it the shortest period roAp star known to date. Four out of the five new roAp stars are multiperiodic. Three of these and the singly periodic one show the presence of rotational mode splitting. Individual frequencies are provided in all cases. In addition, seven previously known roAp stars are analysed. Additional modes of oscillation are found in some stars, while in others we are able to distinguish the true pulsations from possible aliases present in the ground-based data. We find that the pulsation amplitude in the TESS filter is typically a factor of 6 smaller than that in the B filter, which is usually used for ground-based observations. For four roAp stars we set constraints on the inclination angle and magnetic obliquity, through the application of the oblique pulsator model. We also confirm the absence of roAp-type pulsations down to amplitude limits of 6 and 13 mu mag, respectively, in two of the best characterized non-oscillating Ap (noAp) stars. We announce 27 new rotational variables along with their rotation periods, and provide different rotation periods for seven other stars. Finally, we discuss how these results challenge state-of-the-art pulsation models for roAp stars.
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| 5. |
- Diment, Daryna, et al.
(författare)
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A New Methodology to Elucidate Lignin Structure-Properties-Performance Correlation
- 2022
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Konferensbidrag (refereegranskat)abstract
- Unveiling the interrelation between the lignin structure, its properties and performance inspecific applications is of primary importance for lignin engineering for high-value products.Herein, we suggest a new efficient methodology to quantitatively evaluate the roles of ligninspecific functionalities in selected applications. The method is based on changing only onestructural variable at a time, while keeping all others constant prior to performance evaluation.Indulin AT (a softwood Kraft lignin) was subjected to a set of chemical modifications byselectively masking its aliphatic (AlipOH), phenolic OH (PhOH), carboxyl (COOH) andcarbonyl (CO) groups. The property-performance correlation was demonstrated by measuringthe glass transition temperatures (Tg) of the modified lignins. The effect of the modificationson the adsorption performance of the modified lignins was evaluated towards methylene blue.This approach clearly demonstrated that PhOH and AlipOH groups have about equalcontribution (50% each) to the lignin adsorption capacity, while the role of the other functionalgroups is insignificant.
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| 6. |
- Diment, Daryna, et al.
(författare)
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Study toward a More Reliable Approach to Elucidate the Lignin Structure–Property–Performance Correlation
- 2024
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 25:1, s. 200-212
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Tidskriftsartikel (refereegranskat)abstract
- The correlation between lignin structure, its properties, and performance is crucial for lignin engineering in high-value products. Currently, a widespread approach is to compare lignins which differ by more than one parameter (i.e., Kraft vs organosolv vs lignosulfonates) in various applications by attributing the changes in their properties/performance specifically to a certain variable (i.e., phenolic −OH groups). Herein, we suggest a novel approach to overcome this issue by changing only one variable at a time while keeping all others constant before investigating the lignin properties/performance. Indulin AT (Ind-AT), a softwood Kraft lignin, was chosen as the model substrate for this study. Selective (analytical) lignin modifications were used to mask/convert specific functionalities, such as aliphatic (AliphOH) including benzylic −OH (BenzOH) and phenolic −OH (PhOH) groups, carboxyl groups (−COOH) and carbonyl groups (CO) via methylation, acetylation, and reduction. The selectivity and completeness of the reactions were verified by comprehensive NMR analysis (31P and 2D HSQC) of the modified preparations together with state-of-the-art molar mass (MM) characterization. Methylene blue (MB) adsorption, antioxidant activity, and glass transition temperature (Tg) were used to demonstrate and compare the properties/performance of the obtained modified lignins. We found that the contribution of different functionalities in the adsorption of MB follows the trend BenzOH > −COOH > AlipOH > PhOH. Noteworthy, benzylic −OH contributes ca. 3 and 2.3 times more than phenolic and aliphatic −OH, respectively. An 11% and 17% increase of Tg was observed with respect to the unmodified Indulin by methylating benzylic −OH groups and through reduction, respectively, while full acetylation/methylation of aliphatic and phenolic −OH groups resulted in lower Tg. nRSI experiments revealed that phenolic −OH play a crucial role in increasing the antioxidant activity of lignin, while both aliphatic −OH groups and −COOHs possess a detrimental effect, most likely due to H-bonding. Overall, for the first time, we provide here a reliable approach for the engineering of lignin-based products in high value applications by disclosing the role of specific lignin functionalities.
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| 7. |
- Dudarko, Oksana, et al.
(författare)
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Removal of Poly- and Perfluoroalkyl Substances from Natural and Wastewater by Tailored Silica-Based Adsorbents
- 2024
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Ingår i: ACS ES&T Water. - : American Chemical Society.
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Tidskriftsartikel (refereegranskat)abstract
- Per- and polyfluoroalkyl substances (PFAS) are very stable and ubiquitously distributed in terrestrial and aquatic environments, and treatment and remediation techniques for the removal of PFAS are urgently needed. In this study, mesoporous silica matrix SBA-15 grafted with alkyl amino groups was used to remove perfluorooctanoate (PFOA) from aqueous solutions. The amino groups were grafted onto SBA-15 by the condensation of alkyl amino silanes. The synthesized adsorbents were studied by SEM, TEM, IR, low-temperature nitrogen sorption, and XRD. The solid-state and liquid 19F NMR spectroscopy, EDX, and LC-MS/MS results showed high adsorption efficiency and rapid reaction kinetics. In freshly prepared solutions and on the surface of the sorbents, the presence of PFOA micelles was observed. Furthermore, the introduction of amine-containing groups into the structure of the sorbent allows the sorption of up to 649 mg/g of PFOA from solutions. Results showed that the protonated surface amino groups and PFOA interacted electrostatically. The obtained results open perspectives for producing adsorbents for facile extraction of PFAS.
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| 8. |
- Kochukhov, Oleg, et al.
(författare)
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V772 Cas : an ellipsoidal HgMn star in an eclipsing binary
- 2021
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press. - 0035-8711 .- 1365-2966. ; 500:2, s. 2577-2589
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Tidskriftsartikel (refereegranskat)abstract
- The late B-type star V772 Cas (HD10260) was previously suspected to be a rare example of a magnetic chemically peculiar star in an eclipsing binary system. Photometric observations of this star obtained by the TESS satellite show clear eclipses with a period of 5.0137 d accompanied by a significant out-of-eclipse variation with the same period. High-resolution spectroscopy reveals V772 Cas to be an SB1 system, with the primary component rotating about a factor two slower than the orbital period and showing chemical peculiarities typical of non-magnetic HgMn chemically peculiar stars. This is only the third eclipsing HgMn star known and, owing to its brightness, is one of the very few eclipsing binaries with chemically peculiar components accessible to detailed follow-up studies. Taking advantage of the photometric and spectroscopic observations available for V772 Cas, we performed modelling of this system with the PHOEBE code. This analysis provided fundamental parameters of the components and demonstrated that the out-of-eclipse brightness variation is explained by the ellipsoidal shape of the evolved, asynchronously rotating primary. This is the first HgMn star for which such variability has been definitively identified.
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| 9. |
- Mikhraliieva, Albina, et al.
(författare)
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Carbon Nanodots with Solvatochromic Photoluminescence for the Electrochemical Determination of Estrogenic Steroids
- 2022
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Ingår i: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970. ; 5:8, s. 10962-10972
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Tidskriftsartikel (refereegranskat)abstract
- Herein, we utilized carbon nanodots (R-CNDs) for the electrochemical detection of estrogens in tap and natural water samples and simulated effluents from Swedish waste water treatment plants (WWTPs). R-CNDs were prepared from 2-aminophenol by solvothermal synthesis and used as a modifier for chitosan-based selective membranes. The data obtained from atomic force microscopy and transmission electron microscopy suggest a spherical morphology of the R-CNDs with lateral size in the range of 3–8 nm and the height of 1–8 nm. In contrast to most other known carbon nanodots, R-CNDs are soluble in various organic solvents, including apolar, and less soluble in water. Small nanodots (3 nm) are more hydrophilic than large ones (6–8 nm) and can be separated from the bulk suspension of R-CNDs in heptane by their extraction into a water/ethanol mixture. Suspensions of large R-CNDs in apolar solvents exhibit green photoluminescence, while small R-CNDs in polar solvents have orange. This phenomenon was attributed to a solvatochromic rather than to a quantum effect. The R-CNDs were embedded on a chitosan-modified pencil electrode and the electrode was applied for voltammetric determination of four abandoned estrogens: estrone, estradiol, estriol, and ethynyl estradiol. The sensor demonstrates a group-selective response to the estrogens with a detection limit of 17.0 nmol L–1. It can be applied to determine the estrogens in the range of 0.05–4.6 μmol L–1 in the presence of typical interfering bioactive compounds, such as paracetamol, uric acid, progesterone, sulfamethoxazole, trimethoprim, ibuprofen, and caffeine. The developed sensors show repeatability and reproducibility values of 1.8–3.4% and 4.3%, respectively. The efficiency was proved by application for tap and lake water samples, where the recovery range was found to be 93–100%. The low cost, stability, and high sensitivity and selectivity of fabricated sensors make R-CNDs a perspective modifier for electrochemical sensors for the detection of estrogen microquantities in variable water samples.
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| 10. |
- Polishchuk, Liliia M., et al.
(författare)
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In Situ Ring-Opening Polymerization of L-lactide on the Surface of Pristine and Aminated Silica : Synthesis and Metal Ions Extraction
- 2022
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Ingår i: Polymers. - : MDPI. - 2073-4360. ; 14:22
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Tidskriftsartikel (refereegranskat)abstract
- The development of functional materials from food waste sources and minerals is currently of high importance. In the present work, polylactic acid (PLA)/silica composites were prepared by in situ ring-opening polymerizations of L-lactide onto the surface of pristine (Silochrom) and amine-functionalized (Silochrom-NH2) silica. The characteristics of the ring-opening polymerization onto the surface of modified and unmodified silica were identified and discussed. Fourier transform infrared spectroscopy was used to confirm the polymerization of lactide onto the silica surface, and thermogravimetric analysis determined that PLA constituted 5.9% and 7.5% of the composite mass for Silochrom/PLA and Silochrom-NH2/PLA, respectively. The sorption properties of the composites with respect to Pb(II), Co(II), and Cu(II) ions were investigated, and the effect of contact time, initial metal ion concentration, and initial pH were evaluated. Silochrom-NH2/PLA composites were found to have a higher adsorption capacity than Silochrom/PLA for all chosen ions, with the highest adsorption value occurring for Pb2+ at 1.5 mmol/g (90% removal efficiency). The composites showed the highest performance in the neutral or near-neutral pH (created by distilled water or buffer pH 6.86) during the first 15 min of phase contact. The equilibrium characteristics of adsorption were found to follow the Langmuir isotherm model rather than the Freundlich and Temkin models. Perspective applications for these PLA/silicas include remediation of industrial wastewater or leaching solutions from spent lead-acid and Li-ion batteries.
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