| 1. |
- Galkina, Olga, et al.
(author)
-
Antibacterial and photochemical properties of cellulose nanofiber-titania nanocomposites loaded with two different types of antibiotic medicines
- 2015
-
In: Journal of materials chemistry. B. - : Royal Society of Chemistry (RSC). - 2050-750X .- 2050-7518. ; 3:35, s. 7125-7134
-
Journal article (peer-reviewed)abstract
- Nanocomposite dermal drug delivery systems based on cellulose nanofibers with grafted titania nanoparticles loaded by two antibiotic medicines from different classes, i.e. tetracycline (TC) and phosphomycin (Phos), were successfully produced by a "green chemistry'' approach in aqueous media. The influence of a different surface binding mechanism between the drug molecule and modified cellulose nanofibers on the release of the drug and, as a result, on antimicrobial properties against common pathogens Gram-positive, Staphylococcus aureus and Gram-negative Escherichia coli was investigated. The disk diffusion method and broth culture tests using varying concentrations of drugs loaded to nanocomposites were carried out to investigate the antibacterial effects. The influence of UV irradiation on the stability of the obtained nanocomposites and their antibacterial properties after irradiation were also investigated, showing enhanced stability especially for the TC loaded materials. These findings suggest that the obtained nanocomposites are promising materials for the development of potentially useful antimicrobial patches.
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| 2. |
- Agback, Peter, et al.
(author)
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Site-specific recognition of SARS-CoV-2 nsp1 protein with a tailored titanium dioxide nanoparticle - elucidation of the complex structure using NMR data and theoretical calculation
- 2022
-
In: Nanoscale advances. - : Royal Society of Chemistry (RSC). - 2516-0230. ; 4, s. 1527-1532
-
Journal article (peer-reviewed)abstract
- The ongoing world-wide Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) pandemic shows the need for new potential sensing and therapeutic means against the CoV viruses. The SARS-CoV-2 nsp1 protein is important, both for replication and pathogenesis, making it an attractive target for intervention. In this study we investigated the interaction of this protein with two types of titania nanoparticles by NMR and discovered that while lactate capped particles essentially did not interact with the protein chain, the aminoalcohol-capped ones showed strong complexation with a distinct part of an ordered alpha-helix fragment. The structure of the forming complex was elucidated based on NMR data and theoretical calculation. To the best of our knowledge, this is the first time that a tailored titanium oxide nanoparticle was shown to interact specifically with a unique site of the full-length SARS-CoV-2 nsp1 protein, possibly interfering with its functionality.
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| 3. |
- Ahniyaz, Anwar, et al.
(author)
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Preparation of iron oxide nanocrystals by surfactant-free or oleic acid-assisted thermal decomposition of a Fe(III) alkoxide
- 2008
-
In: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 320:6, s. 781-787
-
Journal article (peer-reviewed)abstract
- A new non-hydrolytic, alkoxide-based route was developed to synthesize iron oxide nanocrystals. Surfactant-free thermal decomposition of the iron 2-methoxy-ethoxide precursors results in the formation of uniform iron oxide nanocrystals with an average size of 5.6 nm. Transmission electron microscope study shows that the nanocrystals are protected against aggregation by a repulsive surface layer, probably originating from the alkoxy-alkoxide ligands. Addition of oleic acid resulted in monodisperse nanocrystals with an average size of 4 nm. Mössbauer analysis confirmed that the nanocrystals mainly consisted of maghemite. Analysis of the magnetic hysteresis loop measurements and the zero field and field cooled measurements displayed an excellent fit to established theories for single-domain superparamagnetic nanocrystals and the size of the magnetic domains correlated well to the crystallite size obtained from transmission electron microscope.
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| 4. |
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| 5. |
- Al-Smadi, Derar, 1983-, et al.
(author)
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Chemical and Biochemical Approaches for the Synthesis of Substituted Dihydroxybutanones and Di-, and Tri-Hydroxypentanones
- 2019
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 84:11, s. 6982-6991
-
Journal article (peer-reviewed)abstract
- Polyhydroxylated compounds are building blocks for the synthesis of carbohydrates and other natural products. Their synthesis is mainly achieved by different synthetic versions of aldol-coupling reactions, catalyzed either by organocatalysts, enzymes or metal-organic catalysts. We have investigated the formation of 1,4-substituted 2,3-dihydroxybutan-1-one derivatives from para- and meta-substituted phenylacetaldehydes by three distinctly different strategies. The first involved a direct aldol reaction with hydroxyacetone, dihydroxyacetone or 2-hydroxyacetophenone, catalyzed by the cinchona derivative cinchonine. The second was reductive cross-coupling with methyl or phenyl glyoxal promoted by SmI2 resulting in either 5-substituted 3,4-dihydroxypentan-2-ones or 1,4 bis-phenyl substituted butanones, respectively. Finally, in the third case, aldolase catalysis was employed for synthesis of the corresponding 1,3,4-trihydroxylated pentan-2-one derivatives. The organocatalytic route with cinchonine generated distereomerically enriched syn products (de = 60−99 %), with moderate enantiomeric excesses (ee = 43−56%), but did not produce aldols with either hydroxyacetone or dihydroxyacetone as donor ketones. The SmI2-promoted reductive cross-coupling generated product mixtures with diastereomeric and enantiomeric ratios close to unity. This route allowed for the production of both 1-methyl- and 1-phenylsubstituted 2,3-dihydroxybutanones, at yields between 40−60%. Finally, the biocatalytic approach resulted in enantiopure syn (3R,4S) 1,3,4-trihydroxypentan-2-ones.
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| 6. |
- Ashour, Radwa, et al.
(author)
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DTPA-Functionalized Silica Nano- and Microparticles for Adsorption and Chromatographic Separation of Rare Earth Elements
- 2018
-
In: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 6:5, s. 6889-6900
-
Journal article (peer-reviewed)abstract
- Silica nanoparticles and porous microparticles have been successfully functionalized with a monolayer of DTPA-derived ligands. The ligand grafting is chemically robust and does not appreciably influence the morphology or the structure of the material. The produced particles exhibit quick kinetics and high capacity for REE adsorption. The feasibility of using the DTPA-functionalized microparticles for chromatographic separation of rare earth elements has been investigated for different sample concentrations, elution modes, eluent concentrations, eluent flow rates, and column temperatures. Good separation of the La(III), Ce(III), Pr(III), Nd(III), and Dy(III) ions was achieved using HNO3 as eluent using a linear concentration gradient from 0 to 0.15 M over 55 min. The long-term performance of the functionalized column has been verified, with very little deterioration recorded over more than 50 experiments. The results of this study demonstrate the potential for using DTPA-functionalized silica particles in a chromatographic process for separating these valuable elements from waste sources, as an environmentally preferable alternative to standard solvent-intensive processes.
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| 7. |
- Bedin, Michele, PhD, 1984-
(author)
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Iron, Manganese and Iridium Complexes From Models of RNR and Catalase to Water Oxidation
- 2020
-
Doctoral thesis (other academic/artistic)abstract
- The focus of this thesis has been synthesise and study metal complexes that mimic the structure and function of the active site in two particular metalloenzymes, ribonucleotide reductase (RNR) and manganese catalase (MnCAT). These two metalloenzymes both have two transition metals ions in the cofactor: two manganese ions in MnCAT and either two iron, iron-manganese or two manganese ions in RNR.Three different ligands were synthetized to make model complexes for these cofactors. The first ligand, BPMP, can bind two metal ions and provides two symmetric pockets with two pyridine groups and one amine each, plus a phenolate group that can bridge the two metals. The second ligand DPCPMP had one carboxylate group instead of a pyridine group in one pocket, creating an asymmetric ligand, and the third ligand BPCPMP, had two carboxylate groups, one in each pocket. From the first and the second ligands it was possible to obtain six complexes: low-valent homometallic Mn/Mn and Fe/Fe complexes and a heterometallic complex for each ligand. For the third ligand, only the Fe/Fe complex was synthetized.All seven complexes were characterized by a number of spectroscopic methods. The presence of carboxylate groups in the ligand shifted the redox potential for the metal complexes towards more negative values, particularly in the case of the homometallic Fe/Fe complexes. Surprisingly, for the asymmetric ligand the placement of the metal ions in the two pockets was not dictated by the asymmetry. Additionally, the relative stability of the homometallic complexes versus the heterometallic complexes and the possibility to transform a homometallic complex into a heterometallic complex were investigated. By titrating one metal into a solution containing the other homometallic dimer it was possible to observe that Fe2+ added to a solution of a Mn/Mn complex led to the replacement of one Mn ion in the complex with a Fe ion.The manganese complex of DPCPMP was investigated as a functional model for MnCAT, catalysing the disproportionation of H2O2 to oxygen and water. In the presence of H2O2 this complex also forms a high-valent species with a di-µ-oxo bridge similar to the MnCAT and RNR.Finally, the methodology used for the study of these complexes was also applied to a set of Ir complexes that act as water oxidation catalysts, and we could show that the presence of a pendant group stabilizes the metal at higher oxidation states leading to higher activity for the catalyst.
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| 8. |
- Berggren Kleja, Dan, et al.
(author)
-
Bismuth(III) Forms Exceptionally Strong Complexes with Natural Organic Matter
- 2022
-
In: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 56, s. 3076-3084
-
Journal article (peer-reviewed)abstract
- The use of bismuth in the society has steadily increased during the last decades, both as a substitute for lead in hunting ammunition and various metallurgical applications, as well as in a range of consumer products. At the same time, the environmental behavior of bismuth is largely unknown. Here, the binding of bismuth(III) to organic soil material was investigated using extended X-ray absorption spectroscopy (EXAFS) and batch experiments. Moreover, the capacity of suwannee river fulvic acid (SRFA) to enhance the solubility of metallic bismuth was studied in a long-term (2 years) equilibration experiment. Bismuth(III) formed exceptionally strong complexes with the organic soil material, where >99% of the added bismuth(III) was bound by the solid phase, even at pH 1.2. EXAFS data suggest that bismuth(III) was bound to soil organic matter as a dimeric Bi3+ complex where one carboxylate bridges two Bi3+ ions, resulting in a unique structural stability. The strong binding to natural organic matter was verified for SRFA, dissolving 16.5 mmol Bi per gram carbon, which largely exceeds the carboxylic acid group density of this compound. Our study shows that bismuth(III) will most likely be associated with natural organic matter in soils, sediments, and waters.
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| 9. |
- Breijaert, T. C., et al.
(author)
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Self-assembly of ferria – nanocellulose composite fibres
- 2022
-
In: Carbohydrate Polymers. - : Elsevier Ltd. - 0144-8617 .- 1879-1344. ; 291
-
Journal article (peer-reviewed)abstract
- An environmentally benign synthesis of a magnetically responsive carboxymethylated cellulose nanofibril-based material is reported. Applied experimental conditions lead to the in-situ formation of magnetite nanoparticles with primary particle sizes of 2.0–4.0 nm or secondary particles of 3.6–16.4 nm depending on whether nucleation occurred between individual carboxymethylated cellulose nanofibrils, or on exposed fibril surfaces. The increase in magnetite particle size on the cellulose fibril surfaces was attributed to Ostwald ripening, while the small particles formed within the carboxymethyl cellulose aggregates were presumably due to steric interactions. The magnetite nanoparticles were capable of coordinating to carboxymethylated cellulose nanofibrils to form large “fibre-like” assemblies. The confinement of small particles within aggregates of reductive cellulose molecules was most likely responsible for excellent conservation of magnetic characteristics on storage of this material. The possibility for using the material in drug delivery applications with release rate controlled by daylight illumination is presented. © 2022 The Author(s)
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| 10. |
- Breijaert, Troy C., et al.
(author)
-
Tailoring a bio-based adsorbent for sequestration of late transition and rare earth elements
- 2022
-
In: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 51:47, s. 17978-17986
-
Journal article (peer-reviewed)abstract
- The demand for new renewable energy sources, improved energy storage and exhaust-free transportation requires the use of large quantities of rare earth (REE) and late transition (LTM, group 8–12) elements. In order to achieve sustainability in their use, an efficient green recycling technology is required. Here, an approach, a synthetic route and an evaluation of the designed bio-based material are reported. Cotton-derived nano cellulose particles were functionalized with a polyamino ligand, tris(2-aminoethyl) amine (TAEA), achieving ligand content of up to ca. 0.8 mmol g−1. The morphology and structure of the produced adsorbent were revealed by PXRD, SEM-EDS, AFM and FTIR techniques. The adsorption capacity and kinetics of REE and LTM were investigated by conductometric photometric titrations, revealing quick uptake, high adsorption capacity and pronounced selectivity for LTM compared to REE. Molecular insights into the mode of action of the adsorbent were obtained via the investigation of the molecular structure of the Ni(II)–TAEA complex by an X-ray single crystal study. The bio-based adsorbent nanomaterial demonstrated in this work opens up a perspective for tailoring specific adsorbents in the sequestration of REE and LTM for their sustainable recycling.
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| 11. |
- Daniel, Geoffrey, et al.
(author)
-
Basic Medium Heterogeneous Solution Synthesis of alpha-MnO2 Nanoflakes as an Anode or Cathode in Half Cell Configuration (vs. Lithium) of Li-Ion Batteries
- 2018
-
In: Nanomaterials. - : MDPI AG. - 2079-4991. ; 8
-
Journal article (peer-reviewed)abstract
- Nano alpha-MnO2 is usually synthesized under hydrothermal conditions in acidic medium, which results in materials easily undergoing thermal reduction and offers single crystals often over 100 nm in size. In this study, alpha-MnO2 built up of inter-grown ultra-small nanoflakes with 10 nm thickness was produced in a rapid two-step procedure starting via partial reduction in solution in basic medium subsequently followed by co-proportionation in thermal treatment. This approach offers phase-pure alpha-MnO2 doped with potassium (cryptomelane type K0.25Mn8O16 structure) demonstrating considerable chemical and thermal stability. The reaction pathways leading to this new morphology and structure have been discussed. The MnO2 electrodes produced from obtained nanostructures were tested as electrodes of lithium ion batteries delivering initial discharge capacities of 968 mAh g(-1) for anode (0 to 2.0 V) and 317 mAh g(-1) for cathode (1.5 to 3.5 V) at 20 mA g(-1) current density. At constant current of 100 mA g(-1), stable cycling of anode achieving 660 mAh g(-1) and 145 mAh g(-1) for cathode after 200 cycles is recorded. Post diagnostic analysis of cycled electrodes confirmed the electrode materials stability and structural properties.
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| 12. |
- Daniel, Geoffrey, et al.
(author)
-
Pushing the theoretical capacity limits of iron oxide anodes: capacity rise of γ-Fe2O3 nanoparticles in lithium-ion batteries
- 2016
-
In: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 4, s. 18107-18115
-
Journal article (peer-reviewed)abstract
- Nanoparticles (NPs) of g-Fe2O3 are successfully prepared via facile hydrolysis of a complex iron iodide precursor with subsequent oxidation under mild conditions. When evaluated as an anode material in lithium ion half-cells, electrodes made with gamma-Fe2O3 NPs exhibit excellent rate capabilities with high capacities and good coulombic efficiencies. Electrodes of gamma-Fe2O3 NPs initially deliver capacities of 1100 mA h g1 at 100 mA g1 current density and 980 mA h g1 at 1000 mA g1. Following an activation step of the electrodes, the capacities increase by up to 300 mA h g1 while coulombic efficiencies also improve slightly. At a high current density of 4000 mA g1, a stable capacity of 770 mA h g1 is achieved. In this study, dQ/dv plots are employed to graphically illustrate the capacity breakdown of each cycle into intercalation, conversion, and extra capacity regions. Upon prolonged cycling, the extra capacity region expands to yield higher capacities; this phenomenon has been attributed to both pulverizationinduced particle size reduction and high-rate lithiation-induced activation processes. This study concludes that gamma-Fe2O3 NPs could serve as a promising anode material with comparable results to widely studied alpha-Fe2O3 and Fe3O4 NPs.
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| 13. |
- Gaio, Servane, et al.
(author)
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Nanoceria-nanocellulose hybrid materials for delayed release of antibiotic and anti-inflammatory medicines
- 2022
-
In: Materials Advances. - : Royal Society of Chemistry. - 2633-5409. ; 3:19, s. 7228-7234
-
Journal article (peer-reviewed)abstract
- A novel nanoceria-nanocellulose hybrid material has been developed and evaluated as a potential drug delivery system. Crystalline nanoceria was synthesized in situ in the nanocellulose to obtain a homogenous distribution without extensive particle aggregation. The hybrid materials were loaded with two antibiotic drugs, triclosan and ampicillin, and one anti-inflammatory drug, diclofenac. The bacteriostatic effect on the gram-negative bacteria Escherichia coli was evaluated for the hybrid materials containing triclosan and ampicillin. The nanoceria-nanocellulose hybrid displayed a better retention of ampicillin than triclosan in the disc diffusion test, which is likely due to the presence of the carboxylic acid group in ampicillin that has better affinity for ceria compared to the phenolic group in triclosan. However, drug release studies in solution revealed rapid release of ampicillin and diclofenac, indicative of outer-sphere complexes between ceria and the drugs.
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| 14. |
- Galkina, Olga, et al.
(author)
-
Cellulose nanofiber-titania nanocomposites as potential drug delivery systems for dermal applications
- 2015
-
In: Journal of Materials Chemistry B. - : Royal Society of Chemistry (RSC). - 2050-750X. ; 3, s. 1688-1698
-
Journal article (peer-reviewed)abstract
- In this work, new efficient drug delivery systems based on cellulose nanofiber-titania nanocomposites grafted with three different types of model drugs such as diclofenac sodium, penicillamine-D and phosphomycin were successfully synthesized and displayed distinctly different controlled long-term release profiles. Three different methods of medicine introduction were used to show that various interactions between TiO2 and drug molecules could be used to control the kinetics of long-term drug release. All synthesis reactions were carried out in aqueous media. The morphology, chemical structure and properties of the obtained materials were characterized by SEM, TEM and AFM microscopy, nanoparticle tracking analysis, X-ray diffraction, and TGA analysis. According to FT-IR and UV-Vis spectroscopy data, the titania binds to cellulose nanofibers via formation of ester bonds and to drug molecules via formation of surface complexes. The drug release kinetics was studied in vitro for diclofenac sodium and penicillamine-D spectrophotometrically and for phosphomycin using a radio-labeling analysis with P-33-marked ATP as a model phosphate-anchored biomolecule. The results demonstrated that the obtained nanocomposites could potentially be applied in transdermal drug delivery for anesthetics, analgesics and antibiotics.
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| 15. |
- Galkina, Olga, et al.
(author)
-
The sol-gel synthesis of cotton/TiO2 composites and their antibacterial properties
- 2014
-
In: Surface and Coatings Technology. - : Elsevier BV. - 0257-8972. ; 253, s. 171-179
-
Journal article (peer-reviewed)abstract
- Present work is devoted to investigation of structure and functional properties of hybrid nanomaterials based on the TiO2-modified cellulose fibers of cotton. The titania hydrosol was successfully prepared using the titanium tetraisopropoxide as precursor and the nitric acid as peptizing agent via the low-temperature sol-gel synthesis in aqueous medium and applied to cotton fabric. For cross-linking of titania nanoparticles to cotton the 1,2,3,4-butanetetracarboxylic acid (BTCA) was used as a spacer. The morphology and composition of the surface pure and TiO2 modified cotton fibers were investigated by the scanning electron microscopy (SEM). The cotton/TiO2 composite was characterized by the dielectric permittivity. For the estimation of total titania concentration, all samples were calcined at 650 degrees C The antimicrobial activity of the treated TiO2 cotton fibers was investigated against Escherichia coli as a model Gram-negative bacteria after exposure to UV-irradiation for 10 min. (C) 2014 Elsevier B.V. All rights reserved.
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| 16. |
- Ghosh, Sourav, et al.
(author)
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Investigating the stable operating voltage for the MnFe2O4 Li-ion battery anode
- 2021
-
In: Sustainable Energy & Fuels. - : Royal Society of Chemistry. - 2398-4902. ; 5:6, s. 1904-1913
-
Journal article (peer-reviewed)abstract
- Template-free synthesis of MnFe2O4 nanopowder is carried out by co-precipitation in a basic medium, evaluating the effects of cation ratio and reaction temperature on the phase composition crystallinity of the resulting powder. Single-phase samples of the target spinel are obtained at the stoichiometric Mn : Fe = 1 : 2 ratio under reflux conditions (100 degrees C), as confirmed by X-ray diffraction (XRD) and Fourier Transformed Infrared (FTIR) spectroscopy. Transmission electron microscopy (TEM) images confirmed that nanostructured MnFe2O4 particles are obtained, which is further supported by Debye-Scherrer calculations from XRD data and by AFM measurements. The produced oxide demonstrated considerable thermal stability according to TGA data. Magnetic characteristics are strongly dependent on the content of magnetic phase and phase composition, achieving a maximum of 54 emu g(-1) for single-phase stoichiometric MnFe2O4. Further, the electrochemical stability of this material as the anode is investigated in Li-ion batteries (LIBs). When the MnFe2O4 electrode is operated in the potential window of 0.01-3.0 V, the reversible capacity is enhanced by almost 45% (802 mA h g(-1)) after the 100(th) cycle with reference to the 2(nd) cycle reversible capacity (548 mA h g(-1)). Methodically dQ/dV plots are analyzed and compared to understand processes behind the evolution of extra capacity beyond its theoretical limit. Further, the upper cut-off potential is tuned to identify a stable operating potential window for the MnFe2O4 anode in LIBs.
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| 17. |
- Greco, Gabriele, et al.
(author)
-
Tyrosine residues mediate supercontraction in biomimetic spider silk
- 2021
-
In: Communications materials. - : Springer Science and Business Media LLC. - 2662-4443. ; 2:1
-
Journal article (peer-reviewed)abstract
- Exposing spider silk to wet conditions can cause supercontraction. Here, tyrosine amino acid residues within the amorphous regions are found to contribute to supercontraction, which can be controlled by protein engineering. Water and humidity severely affect the material properties of spider major ampullate silk, causing the fiber to become plasticized, contract, swell and undergo torsion. Several amino acid residue types have been proposed to be involved in this process, but the complex composition of the native fiber complicates detailed investigations. Here, we observe supercontraction in biomimetically produced artificial spider silk fibers composed of defined proteins. We found experimental evidence that proline is not the sole residue responsible for supercontraction and that tyrosine residues in the amorphous regions of the silk fiber play an important role. Furthermore, we show that the response of artificial silk fibers to humidity can be tuned, which is important for the development of materials for applications in wet environments, eg producing water resistant fibers with maximal strain at break and toughness modulus.
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| 18. |
- Greijer, Björn, et al.
(author)
-
Complexes of Keggin POMs [PM12O40](3-) (M=Mo, W) with GlyGlyGly and GlyGlyGlyGly Oligopeptides
- 2021
-
In: European Journal of Inorganic Chemistry. - : Wiley. - 1434-1948 .- 1099-0682. ; , s. 54-61
-
Journal article (peer-reviewed)abstract
- Complexes of Keggin phosphomolybdate and phosphotungstate anions with tri- and tetra-peptides, GlyGlyGly and GlyGlyGlyGly respectively, were isolated and investigated by single crystal X-ray diffraction, FTIR and SEM-EDS in the solid state and by H-1- and P-31 NMR and ESI-MS in solution. The trends imposed by longer chain length and increased hydrophobicity of the peptide molecules were traced both in binding in the solid state and in effects on solution stability of POMs. Hydrolysis of peptides was observed in strongly acidic solutions at enhanced temperatures in the presence of tungsten POMs.
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| 19. |
- Greijer, Björn, et al.
(author)
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Factors influencing stoichiometry and stability of polyoxometalate - peptide complexes
- 2022
-
In: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 51, s. 9511-9521
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Journal article (peer-reviewed)abstract
- In the pursuit of understanding the factors guiding interactions between polyoxometalates (POMs) and biomolecules, several complexes between Keggin phosphomolybdate and diglycine have been produced at different acidity and salinity conditions, leading to difference in stoichiometry and in crystal structure. Principal factors determining how the POM and dipeptide interact appear to be pH, ionic strength of the medium, and the molar ratio of POM to peptide. An important effect turned out to be even the structure-directing role of the sodium cations coordinating carbonyl functions of the peptide bond. Given the interest in applying POMs in biological systems, these factors are highly relevant to consider. In the view of recent interest in using POMs as nano catalysts in peptide hydrolysis also the potential Keggin POM transformation in phosphate buffered saline medium was investigated leading to insight that nanoparticles of zirconium phosphate (ZrP) can be actual catalysts for breakdown of the peptide bond.
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| 20. |
- Greijer, Björn, et al.
(author)
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Functional Nanostructures from Sol–Gel Synthesis Using Keggin Polyoxometallate Phosphotungstic Acid as a Precursor
- 2024
-
In: Inorganic Chemistry. - 0020-1669 .- 1520-510X. ; 63:7, s. 3428-3435
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Journal article (peer-reviewed)abstract
- Subjecting phosphotungstic acid solutions to low pH in combination with introduction of polyvalent cations led to the formation of nanostructured microspheres of approximately 2 μm in size, as shown by scanning electron microscopy, which were almost insoluble and resistant to degradation at neutral and high pH. These microspheres were composed of secondary nanospheres with diameters around 20 nm as revealed by transmission electron microscopy and atomic force microscopy. Investigations of the crystal structure of a potential intermediate of this process, namely, acidic lanthanum phosphotungstate, [La(H2O)9](H3O)3[PW12O40]2(H2O)19, showed a tight network of hydrogen bonding, permitting closer packing of phosphotungstic acid anions, thereby confirming the mechanism of the observed self-assembly process. The new material demonstrated promising electrochemical properties in oxygen evolution reactions with the high stability of the obtained electrode material.
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| 21. |
- Gupta, G., et al.
(author)
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Exploiting Mass Spectrometry to Unlock the Mechanism of Nanoparticle-Induced Inflammasome Activation
- 2023
-
In: Acs Nano. - : AMER CHEMICAL SOC. - 1936-0851 .- 1936-086X. ; 17:17, s. 17451-17467
-
Journal article (peer-reviewed)abstract
- Nanoparticles (NPs) elicit sterile inflammation, but the underlying signaling pathways are poorly understood. Here, we report that human monocytes are particularly vulnerable to amorphous silica NPs, as evidenced by single-cell-based analysis of peripheral blood mononuclear cells using cytometry by time-of-flight (CyToF), while silane modification of the NPs mitigated their toxicity. Using human THP-1 cells as a model, we observed cellular internalization of silica NPs by nanoscale secondary ion mass spectrometry (nanoSIMS) and this was confirmed by transmission electron microscopy. Lipid droplet accumulation was also noted in the exposed cells. Furthermore, time-of-flight secondary ion mass spectrometry (ToF-SIMS) revealed specific changes in plasma membrane lipids, including phosphatidylcholine (PC) in silica NP-exposed cells, and subsequent studies suggested that lysophosphatidylcholine (LPC) acts as a cell autonomous signal for inflammasome activation in the absence of priming with a microbial ligand. Moreover, we found that silica NPs elicited NLRP3 inflammasome activation in monocytes, whereas cell death transpired through a non-apoptotic, lipid peroxidation-dependent mechanism. Together, these data further our understanding of the mechanism of sterile inflammation.
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| 22. |
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| 23. |
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| 24. |
- Kessler, Vadim
(author)
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A family of hexanuclear Mn(III) single-molecule magnets
- 2014
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In: Journal of Coordination Chemistry. - : Informa UK Limited. - 0095-8972 .- 1026-7441 .- 1029-0389. ; 67, s. 3972–3986-
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Journal article (peer-reviewed)abstract
- In an attempt to employ salicylic acid (HOsalH), 2,6-dihydroxy benzoic acid {(HO) naphthalene-1,8-dicarboxylic acid {1,8-naph(CO means to alter the structural identity of the hexanucluear clusters usually obtained from this reaction system, we have isolated a family of hexanuclear Mn(III) complexes based on salicyladloxime (saoH 2-hydroxy-1-naphthaldehyde oxime (naphthsaoH2PhCO2H}, and2H)2} in Mn(III) salicylaldoximate chemistry as a2) and2). Five hexanuclear clusters, [Mn6O2(sao)6(HOsal) 2 ((EtOH)4]·EtOH (1·EtOH), [Mn6O2(sao)6{1,8-naph(CO2Me)(CO2)}2(MeOH)6]·3MeOH2·3MeOH), [Mn6O2(naphthsao)6{1,8-naph(CO2Et)(CO2)}2(EtOH)6] (3·2MeOH), [Mn6O2(naphthsao) 6 ( properties of(MeCO2)2(EtOH)4]·2H2O (4·2H2O), and [Mn6O2(naphthsao)6{(HO)2PhCO2}2(EtOH)4]·4EtOH5·4EtOH), have been synthesized and characterized by single-crystal X-ray crystallography. The magnetic3, 4, and 5 are discussed.
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| 25. |
- Kessler, Vadim
(author)
-
A family of [Ni-8] cages templated by mu(6)-peroxide from dioxygen activation
- 2014
-
In: Inorganic Chemistry Frontiers. - : Royal Society of Chemistry (RSC). - 2052-1545 .- 2052-1553. ; 1, s. 487-494
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Journal article (peer-reviewed)abstract
- A family of exceptionally thermally stable [Ni-8] cages is reported, each being templated by a rare eta(3):eta(3):mu(6)-O-2(2-) species produced by dioxygen activation, where the reducing agent for the O-2 reduction appears to be the ligand used in the reaction mixtures, which was found within the nickel cages in its oxidized form.
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| 26. |
- Kessler, Vadim
(author)
-
A novel route of synthesis of sodium hexafluorosilicate two component cluster crystals using BF4- containing ionic liquids
- 2012
-
In: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 361, s. 51-56
-
Journal article (peer-reviewed)abstract
- The cluster crystals of Na2[SiF6] were obtained in the aqueous solutions of different methylalkylimidazolium(ethyl-, butyl- and decyl-) tetrafluoroborate ionic liquids (IL) in borosilicate glassware. It isdemonstrated that sodium hexafluorosilicate crystalline compounds with good regularity and narrowsize distribution containing dialkyl imidazolium ions between the hexagonal crystalline clustersinterconnected to each other to a whole hexagonal aggregate can be obtained in large quantities. Thischaracteristic phenomenon of crystallization of sodium hexafluorosilicate containing IL ions is reportedfor the first time. The mechanism of formation of various [RMIm]BF4–Na2[SiF6] microcrystallinemorphologies and the influence of temperature on the growth kinetics are discussed. Crystallographicstudies of the product were carried out by X-ray diffractometer (XRD), characterization by scanningelectron microscopy (SEM) and optical microscopies; also infrared spectra (IR) were recorded. Thermalanalysis were performed by differential scanning calorimetry–thermogravimetric analyzer (TGA–DSC).Presence of ionic liquid cations was confirmed by high resolution mass spectrometry (HRMS).
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| 27. |
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| 28. |
- Kessler, Vadim
(author)
-
Alkoxides and Alkoxosynthesis
- 2014
-
In: Comprehensive Inorganic Chemistry II (Second Edition): From Elements to Applications. - 9780080965291 ; , s. 455-470
-
Book chapter (peer-reviewed)abstract
- This chapter summarizes modern approaches in the synthesis of metal alkoxides, provides an overview of their physical and chemical properties, with a special focus on molecular structure and reactivity, and gives a brief but up-to-date presentation of the reaction mechanisms in the synthesis of inorganic materials from metal alkoxides as precursors (alkoxosynthesis). A critical overview of molecular precursor approaches exploiting homo- and heteroleptic alkoxide complexes is provided, explaining the role of heteroligands in nucleation and subsequent growth of the resulting nanostructured materials. This chapter also provides a brief summary of other principal applications of metal alkoxides, such as homogeneous catalysts and molecular magnets, with a special focus on the synthesis and structure of these functional molecules.
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| 29. |
- Kessler, Vadim
(author)
-
Aqueous route to TiO2-based nanomaterials using pH-neutral carboxylate precursors
- 2013
-
In: Journal of Sol-Gel Science and Technology. - : Springer Science and Business Media LLC. - 0928-0707 .- 1573-4846. ; 68, s. 464-470
-
Journal article (peer-reviewed)abstract
- The review presents the industrial and laboratory synthesis, molecular structure and reactivity of titanium( IV) carboxylate complexes stable in aqueous medium. A special accent is made on the solution ligandtransfer equilibria that are able to provide uniform TiO2 nanoparticles under rather mild conditions starting from these easily commercially available species. Application of titanium oxide nanostructures derived from solution-generated titania nanoparticles is described in detail.
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| 30. |
- Kessler, Vadim, et al.
(author)
-
CaptiGel Technology for Encapsulation of Biomaterials and Medicines
- 2009
-
Conference paper (other academic/artistic)abstract
- Inorganic materials receive increasing interest as components and major constituents of encapsulation formulations for bio-molecules and microorganisms. Sol-gel technology is broadly recognized as a versatile synthetic approach to colloidal inorganic materials, perspective as potential hydrosol and hydrogel matrices for encapsulation. The industrial development in this field has been mostly focused on silica in the view of the availability of both organic and inorganic precursors of silica gels and, especially, due to their easy handling and facile control over gelation parameters. Metal oxides have been practically excluded from this application domain, because of the high chemical reactivity and apparent bio-incompatibility of the related precursor chemicals. However, the metal oxides with compositions corresponding to naturally abundant biocompatible minerals, for example titanium dioxide (registered even as the Food Additive E171), can represent an attractive alternative to silica. Stable and biocompatible hydrosols and hydrogels of titanium dioxide and other metal oxides can be successfully prepared using modification of the related metal organic precursors with hydrophilic ligands, especially if the latter can be supplied with electric charge through interaction with acids or bases [1]. The produced colloids are then naturally buffered within biocompatible pH region. An attractive feature of the thus produced colloid particles is that they possess a core-shell structure: the crystalline core contributes with attractive UV-protective properties, while the amorphous shell hinders the negative photochemical activity and permits easy aggregation of the particles into continuous films, self-assembling at any phase boundary, for example, a cell membrane of a microorganism. This permits to produce formulations able to protect the encapsulated biomaterial from both chemical and physical hazards. Another attractive feature of titanium dioxide is its specific biodegradability, offering possibility of enhanced chemically and bio-chemically triggered release [2]. Metal oxide surfaces possess even a pronounced affinity to carboxylate and phosphate/phosphonate functions present in the formula of many important medicines. Release of these drugs after their chemosorption in the oxide hydrogels is a slow and kinetically controlled process sought in many medical applications, which makes the produced materials attractive for drug delivery applications. 1. Kessler, V.G.; Seisenbaeva, G.A.; Håkansson, S.; Unell, M, Metal Oxide Hydrogels and Hydrosols, Their Preparation and Use, PCT application WO07145573. 2. Kessler, V.G.; Seisenbaeva, G.A.; Håkansson, S.; Unell, M, Chemically Triggered Biodelivery Using Metal–Organic Sol–Gel Synthesis. Angew. Chem. Int. Ed., 2008. 47(44): p. 8506-8509
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| 31. |
- Kessler, Vadim
(author)
-
Circular serendipity: in situ ligand transformation for the self-assembly of an hexadecametallic [Cu-16(II)] wheel
- 2014
-
In: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 50, s. 15002-15005
-
Journal article (peer-reviewed)abstract
- A [Cu-16(II)] wheel was isolated serendipitously from the reaction of acetylacetone dioxime with copper(II) chloride and lanthanide ions in a reaction initially designed to produce heterometallic 3d-4f cages. The ligand has been transformed in situ to three different forms, all found within the [Cu-16] wheel, with the original ligand completely absent.
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| 32. |
- Kessler, Vadim
(author)
-
Cu(II) frameworks from a "mixed-ligand" approach
- 2017
-
In: CrystEngComm. - : Royal Society of Chemistry (RSC). - 1466-8033. ; 19, s. 4355-4367
-
Journal article (peer-reviewed)abstract
- Employment of di-2-pyridyl ketone and poly-carboxylates in Cu-II chemistry afforded four complex hydrogen-bonded frameworks, one one-dimensional (1D), one 2D and three 3D coordination polymers. Di-2-pyridyl ketone underwent several metal-assisted transformations to yield three Cu-II structural units which, in combination with the poly-carboxylate anions of the trimesic, isophthalic, 5-hydroxy-isophthalic and pyromellitic acids, provided access to extended frameworks by dative or hydrogen bonds. All nine complex frameworks were realized in terms of their topological analysis. The 3D and the 2D polymers consisted of [Cu-2] dimers and were found to be dominated by ferromagnetic interactions. The origin of the ferromagnetic coupling was attributed to the counter complementarity of the simultaneous alkoxo/syn, syn-carboxylate bridges within the dimers.
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| 33. |
- Kessler, Vadim
(author)
-
CuII Frameworks from Di-2-pyridyl Ketone and Benzene-1,3,5-triphosphonic Acid
- 2018
-
In: European Journal of Inorganic Chemistry. - : Wiley. - 1434-1948 .- 1099-0682. ; , s. 91-98
-
Journal article (peer-reviewed)abstract
- In our effort to develop new synthetic strategies for the isolation of new phosphonate frameworks, we exploited the possibility of simultaneously utilizing benzene-1,3,5-triphosphonic acid (H(6)btp) and di-2-pyridyl ketone (py(2)CO), which is a major player in the field of polynuclear metal complexes. This ligand blend in Cu-II chemistry afforded a 2D framework comprising tetranuclear [Cu-4(II)] secondary building units. A thorough investigation of the Cu-II/di-2-pyridyl ketone/benzene-1,3,5-triphosphonic acid reaction system also revealed a hydrogen-bonded framework. The structure of the latter comprises the cationic [Cu{py(2)C(OH)(2)}(2)](2+) complex [py(2)C(OH)(2) is the hydrate of py(2)CO], the dianion of benzene-1,3,5-triphosphonic acid (H(4)btp(2-)) and water solvates. The magnetic properties of the coordination polymer were rationalized on the basis of magnetically isolated [Cu-4(II)] units dominated by antiferromagnetic interactions.
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| 34. |
- Kessler, Vadim, et al.
(author)
-
Enhanced Removal of Cr(III), Mn(II), Cd(II), Pb(II) and Cu(II) from Aqueous Solution by N-functionalized Ordered Silica
- 2021
-
In: Chemistry Africa. - : Springer Science and Business Media LLC. - 2522-5758 .- 2522-5766. ; 4, s. 451-461
-
Journal article (peer-reviewed)abstract
- Chelating and ion-exchange N-functionalized mesoporous silicas (SBA-15) as selective adsorbents for removal of heavy metals were synthesized using template method. Fourier transform infrared spectroscopy, TEM analysis, N-2 adsorption/desorption isotherms and titration analysis confirmed successful functionalisation of the tri-sodium salt of N-(triethoxysilylpropyl)ethylenediaminetriacetic acid (EDTA), protonated primary amine (NH3+Cl-) and its combinations onto the mesoporous silica (SBA-EDTA/NH2). The obtained materials featured beneficial properties of mesoporous silica SBA-15 with its high surface area and were successfully fictionalized with N-containing groups. The synthesized series of silicas were investigated for removal of Cr(III), Mn(III), Pb(II), Cd(II) and Cu(II) from model water solutions. The adsorption of target ions increased with the increase pH and its concentration in solution. The adsorption equilibrium data were well fitted to Langmuir isotherm model and maximum monolayer adsorption capacities for cations Pb(II), Cd(II), Cr(III) and Mn(II) were 185.6 mg g(-1), 111.2 mg g(-1), 57.7 mg g(-1) and 49.4 mg g(-1), respectively. The chelating interaction was considered as the main adsorption mechanism for metal ions (Cr(III), Mn(II), Pb(II), Cd(II), and Cu(II)). The adsorption capacities of SBA-EDTA and SBA-EDTA/NH2 samples toward studied metal ions were consistent with the Lewis 'hard and soft acids and bases' theory. The metal removal efficiency of adsorbents was near 96-92% during three regeneration cycles. All these results indicated that the produced N-functionalized silica were promising for applications in environmental and analytical separation fields.
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| 35. |
- Kessler, Vadim
(author)
-
Facile non-hydrolytic synthesis of highly water dispersible, surfactant free nanoparticles of synthetic MFe2O4 (M-Mn2+, Fe2+, Co2+, Ni2+) ferrite spinel by a modified Bradley reaction
- 2013
-
In: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 3, s. 12230-12243
-
Journal article (peer-reviewed)abstract
- A series of the highly crystalline MFe2O4 ferrite spinel nanoparticles were synthesized via a modified Bradley reaction using microwave stimulation. Particle size was estimated using theoretical calculations from the X-ray data (Scherrer and Rietveld methods) as well as by direct experimental techniques such as TEM, DLS and NTA. The calculated average grain size for dry powders is in the range 10 to 23 nm. Hydrodynamic size was measured using DLS on non-modified, surfactant free particles of the whole MFe2O4 series. Raman spectra used for additional verification of the structure features of the produced spinel phases showed strong asymmetric behavior of the A(1g) mode, which was deconvoluted revealing additional components. Among all the products the lowest site inversion was found for the manganese ferrite (MnFe2O4). The oxidation of Fe3O4 leading to the formation of the Fe2O3 hematite phase induced by laser irradiation was observed. Magnetic characterization of the MFe2O4 family was carried out, showing that superparamagnetic blocking temperatures and calculated anisotropy constants K are in good agreement with the data for similar fine-particle systems.
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| 36. |
- Kessler, Vadim, et al.
(author)
-
Facile strategies for synthesis of functionalized mesoporous silicas for the removal of rare-earth elements and heavy metals from aqueous systems
- 2021
-
In: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 315
-
Journal article (peer-reviewed)abstract
- A series of adsorbents of SBA-15-type with ethylenediaminetriacetic (EDTA), phosphonic, and ammonium groups as ligands were synthesized using the template method based on sodium metasilicate as the major starting reagent. The detailed characterizations using SEM, TEM, XRD, and N-2 sorption/desorption measurements of synthesized sorbents confirmed an ordered mesopomus structures with uniform pore diameter and large surface area. Regardless of the functional groups concentration, the synthesized sorbents showed significantly higher adsorption capacities for target ions than neat SBA-15. The observed adsorption mechanisms were predominantly based on complexation and electrostatic interactions between metal ions and various functional groups present on the adsorbent surfaces. The synthesized SBA-15 derivatives were used for removal of different metal ions such as Fe(III), Ni(II), Cu(II), Pb(II), Nd(III), and Dy(III) from water (pH >= 1). The highest adsorption capacity was obtained for the bifunctional (-EDTA/phosphonic groups) modified adsorbent, reaching up to 119.05 mg g(-1) for Fe(III), 246.95 mg g(-1) for Pb(II), 246.95 mg g(-1) for Cu(II), 238.10 mg g(-1) for Nd(III) and 243.90 mg g(-1) for Dy(III). The adsorption data were successfully fitted to the Langmuir and Freundlich models, revealing a monolayer chemisorption of REEs on the mesopomus samples. Metal desorption and adsorbent recycling were also found to be efficient under acidic condition (0.5-1.0 M). These properties highlight the perspective uses of functionalized mesoporous silicas for the rapid and potentially selective removal of REEs and heavy metal ions from the complex water samples and technological mixtures.
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| 37. |
- Kessler, Vadim
(author)
-
First principles simulation of reaction steps in the atomic layer deposition of titania: Dependence of growth on Lewis acidity of titanocene precursor
- 2012
-
In: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 14, s. 7954-7964
-
Journal article (peer-reviewed)abstract
- It is a common finding that titanocene-derived precursors do not yield TiO2 films in atomic layerdeposition (ALD) with water. For instance, ALD with Ti(OMe)4 and water gives 0.5 A ˚ /cycle,while TiCp*(OMe)3 does not show any growth (Me = CH3, Cp* = C5(CH3)5). From massspectrometry we found that Ti(OMe)4 occurs in the gas phase practically exclusively as amonomer. We then used first principles density functional theory (DFT) to model the ALDreaction sequence and find the reason for the difference in growth behaviour. Both precursorsadsorb initially via hydrogen-bonding. The simulations reveal that the Cp* ligand ofTiCp*(OMe)3 lowers the Lewis acidity of the Ti centre and prevents its coordination to surface O(‘densification’) during both of the ALD pulses. The effect of Cp* on Ti seems to be both steric(full coordination sphere) and electronic (lower electrophilicity). This crucial step in the sequenceof ALD reactions is therefore not possible in the case of TiCp*(OMe)3 + H2O, which means thatthere is no deposition of TiO2 films.
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| 38. |
- Kessler, Vadim, et al.
(author)
-
Full Tetragonal Phase Stabilization in ZrO2 Nanoparticles Using Wet Impregnation: Interplay of Host Structure, Dopant Concentration and Sensitivity of Characterization Technique
- 2018
-
In: Nanomaterials. - : MDPI AG. - 2079-4991. ; 8
-
Journal article (peer-reviewed)abstract
- Here, we show that wet impregnation of ZrO2 nanoparticles with 10% and 20% Eu oxide followed by thermal anneal in air above 500 degrees C produces full stabilization of the tetragonal phase of ZrO2 without evidencing any phase separation. The bare ZrO2 nanoparticles were obtained using three synthetic methods: oil in water microemulsion, rapid hydrothermal, and citrate complexation methods. The homogeneity of the solid solutions was assessed using X-ray diffraction, Raman spectroscopy, high resolution transmission electron microscopy, and advanced luminescence spectroscopy. Our findings show that wet impregnation, which is a recognized method for obtaining surface doped oxides, can be successfully used for obtaining doped oxides in the bulk with good homogeneity at the atomic scale. The limits of characterization technique in detecting minor phases and the roles of dopant concentration and host structure in formation of phase stabilized solid solutions are also analyzed and discussed.
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| 39. |
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| 40. |
- Kessler, Vadim
(author)
-
Group III quinaldates: synthesis, structure and photoluminescence
- 2017
-
In: Journal of Coordination Chemistry. - : Informa UK Limited. - 0095-8972 .- 1026-7441 .- 1029-0389. ; 70, s. 997-1007
-
Journal article (peer-reviewed)abstract
- The reactions of Al(III), Ga(III) and In(III) nitrates with 2-quinaldic acid (qaH) afforded [Al-2(OH)(2)(qa)(4)]center dot 2H(2)O (1), [Ga(qa)(2)(H2O)(2)]NO3 (2) and [In(qa)(2)(NO3)(H2O)] (3), respectively, in high yields. The crystal structures of 1, 2 and 3 have been determined by single-crystal X-ray crystallography. The structure of 1 features a di-hydroxo bridged [Al-2(mu-OH)(2)](4+) dimer in which each Al(III) is further ligated by two bidentate chelate qa(-) ligands. Complexes 2 and 3 are mononuclear with the M(III) ions in octahedral environments surrounded by two bidentate chelate qa(-) and two H2O in 2 or one H2O and a terminal NO3- in 3. Characteristic IR as well as thermal analysis and solid-state fluorescence are discussed.[GRAPHICS].
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| 41. |
- Kessler, Vadim
(author)
-
High-spin Ni(II) clusters: triangles and planar tetranuclear complexes
- 2011
-
In: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 40, s. 4590-4598
-
Journal article (peer-reviewed)abstract
- The exploration of the NiX2/py(2)CO/Et3N ( X= F, Cl, Br, I; py(2)CO = di-2-pyridyl ketone; Et3N = triethylamine) reaction system led to the tetranuclear [Ni4Cl2{py(2)C(OH)O}(2){py(2)C(OMe)O}(2)(MeOH)(2)]Cl-2 center dot 2Et(2)O (1 center dot 2Et(2)O) and [Ni4Br2{py(2)C(OH)O}(2){py(2)C(OMe)O}(2)(MeOH)(2)]Br-2 center dot 2Et(2)O (2 center dot 2Et(2)O) and the trinuclear [Ni-3{py(2)C(OMe)O}(4)]I-2 center dot 2.5MeOH (3 center dot 2.6MeOH), [Ni-3{py(2)C(OMe)O}(4)](NO3)(0.65)I-1.35 center dot 2MeOH (4 center dot 2MeOH) and [Ni-3{py(2)C(OMe)O}(4)](SiF6)(0.8)F-0.4 center dot 3.5MeOH (5 center dot 3.5MeOH) aggregates. The presence of the intermediate size Cl- and Br- anions resulted in planar tetranuclear complexes with a dense hexagonal packing of cations and donor atoms (tetramolybdate topology) where the X-anions participate in the core acting as bridging ligands. The F- and I- anions do not favour the above arrangement resulting in triangular complexes with an isosceles topology. The magnetic properties of 1-3 have been studied by variable-temperature dc, variable-temperature and variable-field ac magnetic susceptibility techniques and magnetization measurements. All complexes are high-spin with ground states S = 4 for 1 and 2 and S = 3 for 3.
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| 42. |
- Kessler, Vadim, et al.
(author)
-
In situ Functionalized Mesoporous Silicas for Sustainable Remediation Strategies in Removal of Inorganic Pollutants from Contaminated Environmental Water
- 2022
-
In: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 7, s. 23576-23590
-
Journal article (peer-reviewed)abstract
- Low-cost mesoporous silicas of the SBA-15 family were prepared, aimed for removal of a broad spectrum of both cationic and anionic forms of hazardous metal pollutants (Cr(III, VI), Mn(II, VII), Pb(II), Cd(II), and Cu(II)) from environmental water. Series of mono-and bifunctional materials with immobilized ethylenediaminetriacetic acid (EDTA), primary amine (NH2), and quaternary ammonium (QAS) groups were prepared in a cost-efficient one-step synthesis using two silica sources, low-cost sodium metasilicate (Na2SiO3 9H(2)O) and the conventional source-tetraethylorthosilicate (TEOS). The functionalized SBA-15 samples obtained from both silica sources were highly ordered, as evidenced by TEM and SAXS data. All obtained materials were mesoporous with high surface area values of up to 745 m(2)/g, pore volumes from 0.99 to 1.44 cm(3)/g, and narrow pore distributions near 7 nm. The adsorption affinity of the EDTA-functionalized samples followed the common order Pb(II)> Cd(II)> Cu(II)> Cr(III)> Mn(II), which could be explained based on the Pearson theory. The highest adsorption capacities were observed for samples functionalized by EDTA groups using TEOS for synthesis (TEOS/EDTA): 195.6 mg/g for Pb(II), 111.2 mg/g for Cd(II), 58.7 mg/ g for Cu(II), 57.7 mg/g for Cr(III), and 49.4 mg/g for Mn(II). Moreover, organic matter (humic acid up to 10 mg/L) and inorganic (Na(I), K(I), Mg(II), Ca(II), etc) macrocomponents present in environmental water had almost negligible effect on the removal of these cations. The NaSi/EDTA/NH2 sample revealed a better selectivity compared to the NaSi/NH2 sample towards such species as Cr(III), Mn(II), Cd(II), and Cu(II). The chromate-ions uptake at pH 7.5 by the TEOS/QAS sample turned practically unaffected by the presence of doubly charged anions (CO32-, SO42-). The content of functional groups on the surface of MS decreased only slightly (similar to 1-5%) after several regeneration cycles. The complete desorption of all heavy metal ions can be achieved using 1 mol/L EDTA solution. Reusability tests demonstrated the complete stability of the adsorbent for at least five to six consecutive adsorption/ desorption cycles with no decrease in its adsorption characteristics compared to those obtained by 0.05 mol/L HNO3 treatments. The synthesized mesoporous materials were evaluated for removal of the heavy metal ions from drinking and different natural water samples, proving their potential as sustainable, effective, and cost-efficient adsorbents.
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| 43. |
- Kessler, Vadim, et al.
(author)
-
Methodical Thermolysis of [Ba2Ti2(thd)(4)(OnPr)(8)(nPrOH)(2)] under Autogenous Pressure Followed by Combustion for the Synthesis of Dielectric Tetragonal BaTiO3 Nanopowder
- 2009
-
In: Chemistry - An Asian Journal. - : Wiley. - 1861-4728 .- 1861-471X. ; 4, s. 1084-1091
-
Journal article (peer-reviewed)abstract
- The tetragonal BaTiO3 nanopowder is synthesized in a solvent-less, efficient process by the thermolysis of a single [Ba2Ti2(thd)(4)(OnPr)(8)(nPrOH)(2)] precursor in a closed reactor at 700 degrees C under autogenous pressure, followed by combustion. This paper compiles the synthesis of the [Ba2Ti2(thd)(4)(OnPr)(8)(nPrOH)(2)] precursor, its analysis by mass spectrometry, and implementation for the fabrication of dielectric tetragonal BaTiO3 nanopowder by controlled efficient thermal decomposition. The as-prepared, intermediate, and final forms of the obtained nanomaterials are systematically analysed by XRD, Raman, and EDS measurements to gain structural and compositional information. Employing HR-SEM, TEM, and HR-TEM techniques, the morphological changes during the structural evolution of all the phases are pursued. The mechanistic elucidation for the fabrication of BaTiO3 nanopowder is developed on the basis of TGA and DTA data obtained for the initial [Ba2Ti2(thd)(4)(OnPr)(8)(nPrOH)(2)] reactant as well as the as prepared BaCO3 With amorphous Ti phase.
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| 44. |
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| 45. |
- Kessler, Vadim
(author)
-
Molecular Mechanisms in Metal Oxide Nanoparticle Interactions with Biomolecules
- 2020
-
In: The minerals, metals & materials series. - Cham : Springer International Publishing. - 2367-1181 .- 2367-1696. ; , s. 845-853
-
Conference paper (peer-reviewed)abstract
- Metal oxide nanoparticles (NPs) are common in the environment originating on weathering of minerals both in marine and freshwater environments and in soil. Their effects on living organisms are important in view of complex surface chemistry and enhanced surface-to-volume ratio. In the present contribution, three major effects of NP will be considered-(1) their role in mediating interactions between soil microorganisms and plant roots with strong contribution to biofilm formation, (2) the catalytic effects in plant tissues, where NP can act as nanozymes, and (3) specific protein adsorption, resulting in the formation of scaffolds for tissue regeneration. Major tools in this work have been X-ray single crystal, NMR, and electrospray mass spectrometry studies of oxide "cluster" models bearing selected biomolecular ligands.
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| 46. |
- Kessler, Vadim, et al.
(author)
-
Molecular mechanisms of the metal oxide sol-gel process and their application in approaches to thermodynamically challenging complex oxide materials
- 2023
-
In: Journal of Sol-Gel Science and Technology. - 0928-0707 .- 1573-4846. ; 107, s. 190-200
-
Journal article (peer-reviewed)abstract
- This review presents a brief overview of recent insights into general reaction pathways in sol-gel synthesis of metal oxides. Metal-based sol-gel precursors display kinetically unhindered reactivity, combining high reaction speed with reversibility on a molecular level. The process producing metal oxide sols can thus be described as nucleation of an oxide phase with growth option efficiently precluded by extremely low solubility. The emerging nuclei are essentially Polyoxometalate (POM) species, with sizes in the colloid range starting from about 2 nm. They are stabilized in solution by colloid forces (charge interactions, hydrogen bonding, van der Waals forces), defined by the nature and arrangement of species on their surface, which permits them to be denoted as Micelles Templated by Self-Assembly of Ligands (MTSALs). The sol-gel transition occurs on aggregation of particles resulting in percolation. Exploiting this mechanism, it is possible to produce materials with controlled porosity, biocompatibility, and even to access thermodynamically challenging phases that cannot be produced by conventional synthetic techniques.
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| 47. |
- Kessler, Vadim
(author)
-
Mononuclear gallium(III) complexes based on salicylaldoximes: Synthesis, structure and spectroscopic characterization
- 2009
-
In: Polyhedron. - : Elsevier BV. - 0277-5387. ; 28, s. 3291-3297
-
Journal article (peer-reviewed)abstract
- The reactions of Ga(acac)(3) with salicylaldoxime (saoH(2)) and methyl-salicylaldoxime (Me-saoH(2)) in dichloromethane/hexane afforded the complexes [Ga(acac)(saoH)(2)] (1) and [Ga(acac)(3)][Ga(acac)(MesaoH)(2)] (2), respectively, in high yields. The crystal structures of I and 2 have been determined by single-crystal X-ray crystallography. Both complexes are mononuclear with the Ga(Ill) atoms being in octahedral environments surrounded by two bidentate chelate R-saoH(-) and one bidentate chelate acac(-) ligands. A [Ga(acac)(3)] moiety has co-crystallized along with the methylsalicylaldoximato complex. Characteristic IR as well as NMR data are discussed in terms of the nature of bonding in the structures of the two complexes. (1)H and (13)C NMR data in CDCl(3) indicate that the salicylaldoximato, complexes isomerize in solution. (C) 2009 Elsevier Ltd. All rights reserved.
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| 48. |
- Kessler, Vadim
(author)
-
Nanoparticle Self-Assembly Mechanisms in the Colloidal Synthesis of Iron Titanate Nanocomposite Photocatalysts for Environmental Applications
- 2016
-
In: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 4, s. 2814–2821-
-
Journal article (peer-reviewed)abstract
- Colloidal synthesis of iron titanate based nanocomposites exploiting interaction of solutions of binary oxide nanoparticles, Fe2O3 and TiO2, was investigated with respect to the pH of the reaction medium and the conditions used for the synthesis of the reactants. It has been demonstrated that while the phase composition of the products is rather analogous, involving formation of iron titanate phases on the grain boundaries of the binary oxide particles, the morphology of the resulting aggregates can be a matter of pH-control. The self-assembly mechanisms are guided by the surface charge of the particles, offering nano rod regular colloid crystal structures of altering particles with opposite initial charges at neutral pH and globular aggregates with random distribution of uniformly charged particles at low pH as revealed by DLS and high resolution TEM studies. The produced materials demonstrated enhanced photocatalytic activity compared to iron titanates produced by conventional techniques. Magnetic characteristics have also been investigated disclosing possibility of magnetic separation for the Fe2TiO5 material, making it an attractive candidate for application in sustainable remediation of wastewaters.
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| 49. |
- Kessler, Vadim, et al.
(author)
-
Nanoscale insights into doping behavior, particle size and surface effects in trivalent metal doped SnO2
- 2017
-
In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7
-
Journal article (peer-reviewed)abstract
- Despite considerable research, the location of an aliovalent dopant into SnO2 nanoparticles is far to be clarified. The aim of the present study on trivalent lanthanide doped SnO2 is to differentiate between substitutional versus interstitial and surface versus bulk doping, delineate the bulk and surface defects induced by doping and establish an intrinsic dopant distribution. We evidence for the first time a complex distribution of intrinsic nature composed of substitutional isolated, substitutional associates with defects as well as surface centers. Such multi-modal distribution is revealed for Eu and Sm, while Pr, Tb and Dy appear to be distributed mostly on the SnO2 surface. Like the previously reported case of Eu, Sm displays a long-lived luminescence decaying in the hundreds of ms scale which is likely related to a selective interaction between the traps and the substitutional isolated center. Analyzing the time-gated luminescence, we conclude that the local lattice environment of the lattice Sn is not affected by the particle size, being remarkably similar in the similar to 2 and 20 nm particles. The photocatalytic measurements employed as a probe tool confirm the conclusions from the luminescence measurements concerning the nature of defects and the temperature induced migration of lanthanide dopants.
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| 50. |
- Kessler, Vadim, et al.
(author)
-
Optically Active Hybrid Materials Based on Natural Spider Silk
- 2019
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In: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 11, s. 22962-22972
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Journal article (peer-reviewed)abstract
- Spider silk is a natural material possessing unique properties such as biocompatibility, regenerative and antimicrobial activity, and biodegradability. It is broadly considered an attractive matrix for tissue regeneration applications. Optical monitoring and potential control over tissue regrowth are attractive tools for monitoring of this process. In this work, we show upconversion modification of natural spider silk fibers with inorganic nanoparticles. To achieve upconversion, metal oxide nanoparticles were doped with low concentrations of rare-earth elements, producing potentially biocompatible luminescent nanomaterials. The suggested approach to spider silk modification is efficient and easy to perform, opening up sensing and imaging possibilities of biomaterials in a noninvasive and real-time manner in bio-integration approaches.
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