| 31. |
- Nuri, Ayat, et al.
(författare)
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Synthesis and Characterization of Palladium Supported Amino Functionalized Magnetic-MOF-MIL-101 as an Efficient and Recoverable Catalyst for Mizoroki–Heck Cross-Coupling
- 2020
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Ingår i: Catalysis Letters. - : Springer. - 1011-372X .- 1572-879X. ; 150:9, s. 2617-2629
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic particles were prepared by a hydrothermal method and then successively covered by Metal–Organic-Frameworks MIL-101-NH2 with a high surface area. This was followed by deposition of Pd(OAc)2 on Fe3O4–NH2@MIL-101-NH2 particles. The final catalyst was characterized with FT-IR, nitrogen physisorption, thermogravimetry (TGA), scanning electron microscopy (SEM) combined with energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), wide-angle X-ray diffraction spectroscopy (XRD) and X-ray photoelectron spectroscopy (XPS). The prepared magnetic catalyst was effectively used in the Heck coupling reaction in the presence of an inorganic base. The reaction parameters such as the base type, amounts of catalyst and solvents, temperature, and substrates ratios were optimized. The catalyst was then magnetically separated, washed, and reused 7 times without losing significantly catalytic activity.
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| 32. |
- Ramstedt, Madeleine, et al.
(författare)
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Bacterial surfaces in geochemistry : how can x-ray photoelectron spectroscopy help?
- 2019
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Ingår i: Analytical geomicrobiology. - Cambridge : Cambridges Institutes Press. - 9781107070332 - 9781107707399 ; , s. 262-287
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Processes occurring at surfaces and interfaces are very important in environmental systems, necessitating surface-specific characterization tools that can help us understand processes at and specific properties of surfaces and interfaces, and their role in biogeochemical systems. This chapter describes the use and application of X-ray photoelectron spectroscopy (XPS) to study interfacial processes of relevance for geomicrobiology. Examples are given from studies determining cell wall composition, acid–base properties, cell surface charge, metal adsorption onto bacterial cells, and bacterial surface–induced precipitation of secondary minerals. As XPS is an ultrahigh-vacuum technique, several sample preparation methods have been applied to enable analysis of bacterial samples, including analysis of freeze-dried samples as well as frozen bacterial suspensions. These are described and discussed alongside advantages and disadvantages of different approaches, with a special focus on fast-freezing and the cryogenic technique.
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| 33. |
- Shukla, Shashi Kant, 1983-, et al.
(författare)
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Melting point of ionic liquids
- 2020
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Ingår i: Encyclopedia of ionic liquids. - Singapore : Springer. - 9789811067396 ; , s. 1-9
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 34. |
- Škvarla, Jiří, et al.
(författare)
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Cryo-XPS : A new technique for the quantitative analysis of the structure of electric double layer at colloidal particles?
- 2020
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Ingår i: Colloids and Surfaces A. - : Elsevier. - 0927-7757 .- 1873-4359. ; 586
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Tidskriftsartikel (refereegranskat)abstract
- There is a long-lasting uncertainty as to the structure of the metal oxide/water interface. Various structures have especially been invoked to rationalize the seemingly anomalous silica/water interface. But, none of them seems to be approved in a quantitative and systematic way. We show that the concentration ratio of monovalent counterions and coions around colloidal silica spheres, as detected by the cryo-XPS technique, follows fundamental theoretical predictions of either Boltzmann or Donnan distribution. It is suggested that the reason of the dual response is the formation of the swelling gel layer on the silica surface due to its longer contact with water.
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| 35. |
- Tehrani, Ali, 1976, et al.
(författare)
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Solubilization of hydrophobic dyes in surfactant solutions
- 2013
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Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 6:2, s. 580-608
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Forskningsöversikt (refereegranskat)abstract
- In this paper, the use of surfactants for solubilization of hydrophobic organic dyes (mainly solvent and disperse dyes) has been reviewed. The effect of parameters such as the chemical structures of the surfactant and the dye, addition of salt and of polyelectrolytes, pH, and temperature on dye solubilization has been discussed. Surfactant self-assemble into micelles in aqueous solution and below the concentration where this occurs-the critical micelle concentration (CMC)-there is no solubilization. Above the CMC, the amount of solubilized dye increases linearly with the increase in surfactant concentration. It is demonstrated that different surfactants work best for different dyes. In general, nonionic surfactants have higher solubilization power than anionic and cationic surfactants. It is likely that the reason for the good performance of nonionic surfactants is that they allow dyes to be accommodated not only in the inner, hydrocarbon part of the micelle but also in the headgroup shell. It is demonstrated that the location of a dye in a surfactant micelle can be assessed from the absorption spectrum of the dye-containing micellar solution.
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| 36. |
- Yun, Jingwei, et al.
(författare)
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Surface Composition Dependence on the Ice Nucleating Ability of Potassium-Rich Feldspar
- 2020
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Ingår i: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 4:6, s. 873-881
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Tidskriftsartikel (refereegranskat)abstract
- Mineral dust particles are one of the most abundant types of ice nucleating particles in the atmosphere. During atmospheric transport, these particles can be coated with water-soluble solutes, which can modify their ice nucleating ability. Although previous studies have shown that even low concentrations of water-soluble solutes can modify the ice nucleating properties of mineral dust particles, our understanding of this topic is far from complete. We examined the effects of a series of alkali metal nitrates at low concentrations (5 × 10–5 M to 5 × 10–3 M) on the surface composition and immersion freezing of potassium-rich feldspar (K-rich feldspar). Immersion freezing was investigated with the droplet freezing technique, and the surface composition was investigated with cryogenic X-ray photoelectron spectroscopy. K+ increased the median freezing temperature of the droplets, while the other alkali metal cations either had no effect or decreased the median freezing temperature. The changes in the median freezing temperature of the droplets due to the presence of nitrates followed the order K+ ≥ Li+ ≥ Na+ ≥ Rb+ ≥ Cs+ and, except for Cs+, were correlated to the K/Al ratio at the surface of K-rich feldspar. The K/Al ratio is possibly an indicator of the abundance of certain types of K-bearing microcline surfaces that drive the immersion freezing of K-rich feldspar, while Cs+ likely influences the immersion freezing of K-rich feldspar by an additional mechanism, possibly blocking ice nucleation sites by adsorption. Our work also shows that the cation charge density (charge density over the surface area of a single cation) is not a good predictor of the effects of cations on the immersion freezing of K-rich feldspar in our experiments.
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| 37. |
- Amombo Noa, Francoise Mystere, 1988, et al.
(författare)
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A hexagon based Mn(ii) rod metal-organic framework - structure, SF 6 gas sorption, magnetism and electrochemistry
- 2023
-
Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1364-548X .- 1359-7345. ; 59:15, s. 2106-2109
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Tidskriftsartikel (refereegranskat)abstract
- A manganese(ii) metal-organic framework based on the hexatopic hexakis(4-carboxyphenyl)benzene, cpb6−: [Mn3(cpb)(dmf)3], was solvothermally prepared showing a Langmuir area of 438 m2 g−1, rapid uptake of sulfur hexafluoride (SF6) as well as electrochemical and magnetic properties, while single crystal diffraction reveals an unusual rod-MOF topology.
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| 38. |
- Bergman, Jenny, et al.
(författare)
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Counting the number of enzymes immobilized onto a nanoparticle-coated electrode
- 2018
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 410:6, s. 1775-1783
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Tidskriftsartikel (refereegranskat)abstract
- To immobilize enzymes at the surface of a nanoparticle-based electrochemical sensor is a common method to construct biosensors for non-electroactive analytes. Studying the interactions between the enzymes and nanoparticle support is of great importance in optimizing the conditions for biosensor design. This can be achieved by using a combination of analytical methods to carefully characterize the enzyme nanoparticle coating at the sensor surface while studying the optimal conditions for enzyme immobilization. From this analytical approach, it was found that controlling the enzyme coverage to a monolayer was a key factor to significantly improve the temporal resolution of biosensors. However, these characterization methods involve both tedious methodologies and working with toxic cyanide solutions. Here we introduce a new analytical method that allows direct quantification of the number of immobilized enzymes (glucose oxidase) at the surface of a gold nanoparticle coated glassy carbon electrode. This was achieved by exploiting an electrochemical stripping method for the direct quantification of the density and size of gold nanoparticles coating the electrode surface and combining this information with quantification of fluorophore-labeled enzymes bound to the sensor surface after stripping off their nanoparticle support. This method is both significantly much faster compared to previously reported methods and with the advantage that this method presented is non-toxic.
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| 39. |
- Boge, Lukas, 1987
(författare)
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Lipid-based liquid crystals as drug delivery vehicles for antimicrobial peptides
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The development of antimicrobial resistance is a great challenge within the health sector around the world. The demand for new efficient treatments is alarming in order to treat various bacterial infections in the near future. Antimicrobial peptides (AMPs) are a group of novel antibiotics that have gain more and more attraction the past decade. However, AMPs suffers from relatively low stability due to proteolytic and chemical degradation. As a consequence, carrier systems protecting the AMPs are highly needed for achieving efficient treatments. In this thesis, lyotropic liquid crystalline (LC) structures consisting of cubic glycerol monooleate/water and hexagonal glycerol monooleate/oleic acid/water have been examined as carriers for three AMPs (AP114, DPK-060 and LL-37). Both bulk gels and discrete dispersed structures, i.e. cubosomes and hexosomes have been studied. Moreover, two different peptide loading approaches for the cubosomes were tested and compared; pre- and post-loading. Characterization of the LC structures was performed using small-angle x-ray scattering (SAXS), dynamic light scattering, ζ-potential, and cryogenic transmission electron microscopy (Cryo-TEM) and peptide loading efficacy by liquid chromatography. The antimicrobial effect of the AMP loaded LC nanoparticles (LCNPs) was studied in vitro using minimum inhibitory concentration (MIC) and time-kill assays. Proteolytic protection was investigated by incubating the formulations with two elastases and the antimicrobial effect after proteolysis was studied using radial diffusion assay (RDA). Results showed that the most hydrophobic peptide (AP114) was prone to induce an increase in negative curvature of the bulk cubic LC gel, hence pushing the system towards a hexagonal structure. The most polar peptide (DPK-060) induced a decrease in negative curvature while LL-37 did not change the LC phase at all. The hexagonal LC phase was not affected by any of the AMPs. The cubic pre- and post-loaded LCNPs displayed promising antimicrobial activity, and sometimes could a synergetic effect be observed, resulting in a slightly better activity than the unformulated AMP. The hexagonal LCNPs were found to be very efficient in encapsulating the AMPs, but did not display any antimicrobial effect, indicating insufficient delivery of peptide to the bacteria. Moreover, cubosomes post-loaded with LL-37 was found to protect the peptide from proteolytic degradation, resulting in a significant better bactericidal effect after proteolysis.
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| 40. |
- Busch, Michael, 1983, et al.
(författare)
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Water Oxidation on MnOx and IrOx: Why Similar Performance?
- 2013
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 117:1, s. 288-292
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Tidskriftsartikel (refereegranskat)abstract
- The critical steps in water oxidation at a binuclear Mn(II–IV) oxide site are revisited. Ideal stabilities of intermediates are confirmed by comparing to results for a binuclear Ir(III–V) system. The latter in turn is known to be an excellent water oxidation catalyst. The inefficiency of the binuclear Mn(II–IV) site is owing to the high activation energy for the chemical step whereby MnIV═O double bonds on adjacent sites are broken prior to forming the MnIII—O—O—MnIII peroxy moiety. A rationale for Mn(II–IV)—Mn(III–V) mixed oxidation state for water oxidation catalysis, analogous to mixed transition metal oxide systems, is offered. Possible virtues of the kinetic stability of the binuclear MnIV═O moiety are discussed, utilizing its oxidizing power by sidestepping oxygen evolution.
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