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1.	Maurina Morais, Eduardo, 1989, et al. (författare) Solvent-free synthesis of protic ionic liquids. Synthesis, characterization and computational studies of triazolium based ionic liquids 2022 Ingår i: Journal of Molecular Liquids. - : Elsevier BV. - 0167-7322. ; 360 Tidskriftsartikel (refereegranskat)abstract A series of triazolium and imidazolium based protic ionic liquids were synthesized using a solvent-free method designed to address several limitations encountered with other commonly used methods. Using this method, pure (98–99% m/m) and dry (128–553 ppm of water) protic ionic liquids were synthesized (in a laboratory scale) without the need for purification methods that require heating the ionic liquid, hence avoiding the common issue of thermal decomposition. This method was also designed to allow for the accurate measurement of acid and base, and for the controlled mixing of both compounds, which is essential to avoid producing impure protic ionic liquids with excess of either acid or base. The system is constructed of only glass and chemically resistant polymer (PTFE and PVDF) parts, which avoid other contaminants that can result from unwanted reactions involving the reagents with common laboratory tools (metallic objects, paper, plastic, etc.). This process is described in detail in the paper as well as in a video. The resulting ionic liquids were carefully analyzed by spectroscopic and thermal methods designed to avoid water absorption, which is known to affect their properties. To complement this experimental characterization, computational chemistry tools were used to assess the ionic liquids’ properties, as well as to assign vibrational modes.
2.	Sauer, Christopher, 1993 (författare) Green Aromatics: Catalytic Valorisation of bio-derived 2,5-dimethylfuran over Zeolites and Zeotypes 2022 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract This thesis discusses the use of biomass as a potentially green feedstock for the chemical industry in the urgent shift away from fossil resources. I elaborate on reasons why we cannot afford to burn virgin biomass for energy production, among them a variety of ecosystem services that forests and other lands provide. In addition, the utilisation of biomass should be focused on products that sequester and lock away carbon for more extended periods, e.g. timber, materials and chemicals. In particular, biomass can be used as an alternative "carbon neutral" feedstock for the chemical industry, where we can preserve the already existing chemical complexity in the bio-based molecules. One example is the upgrading of furans to benzene, toluene and xylene (BTX) aromatics with the help of zeolite catalysis. These aromatics are important commodity chemicals, where the shift to a bio-based resource could make use of already existing knowledge, catalyst and production infrastructure. However, research is necessary to understand these new feedstock molecules and their interaction with the catalysts and to enable the design of applicable catalysts. In order to study the interaction of the furans, in particular 2,5-dimethylfuran (2,5-dmf), I describe and discuss the development of an analytical methodology that utilises infrared spectroscopy and mass spectrometry for the on-line identification and quantification of product molecules during catalytic reactions. This on-line analysis method is then applied to the catalytic conversion of 2,5-dmf to aromatics over a range of zeolite and zeotype catalysts. In-depth studies with ammonia as a probe molecule of the catalytic active acid sites, as well as temperature programmed experiments with ammonia and 2,5-dmf give insights into product distribution, selectivity changes and deactivation of the catalyst. For example, olefins and aromatics are initially preferred products, while with increasing time on stream, the isomerisation of 2,5-dmf becomes dominant. The incorporation of Ga into the zeotype framework, resulting in a Ga-Silicate, shows how targeted catalyst design can increase overall aromatics production. This catalyst is also suitable for selective isomerisation of 2,5-dmf to 2,4-dimethylfuran, which has a rare substitution pattern. Finally, itwas found that the most valuable of BTX, p -xylene, can be produced more selectively when 2,5-dmf is pre-adsorbed onto zeolite ZSM-5 and then released during a temperature programmed product desorption.
3.	Guo, Y., et al. (författare) Reversible Structural Isomerization of Nature's Water Oxidation Catalyst Prior to O-O Bond Formation 2022 Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 144:26, s. 11736-11747 Tidskriftsartikel (refereegranskat)abstract Photosynthetic water oxidation is catalyzed by a manganese-calcium oxide cluster, which experiences five "S-states" during a light-driven reaction cycle. The unique "distorted chair"-like geometry of the Mn4CaO5(6)cluster shows structural flexibility that has been frequently proposed to involve "open" and "closed"-cubane forms from the S1 to S3states. The isomers are interconvertible in the S1 and S2states, while in the S3state, the open-cubane structure is observed to dominate inThermosynechococcus elongatus (cyanobacteria) samples. In this work, using density functional theory calculations, we go beyond the S3+Yzstate to the S3nYz•→ S4+Yzstep, and report for the first time that the reversible isomerism, which is suppressed in the S3+Yzstate, is fully recovered in the ensuing S3nYz•state due to the proton release from a manganese-bound water ligand. The altered coordination strength of the manganese-ligand facilitates formation of the closed-cubane form, in a dynamic equilibrium with the open-cubane form. This tautomerism immediately preceding dioxygen formation may constitute the rate limiting step for O2formation, and exert a significant influence on the water oxidation mechanism in photosystem II.
4.	Singh, Shivangi, 1996 (författare) Investigating hydrothermal stability and influence of water on the activity of Cu-CHA catalysts for NH3-SCR 2024 Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract Selective catalytic reduction of nitrogen oxides (NOx) with NH3 as a reducing agent (NH3- SCR) is a leading technology for diesel exhaust emission control. Cu-exchanged zeolites with the chabazite structure (Cu-CHA) have emerged as the preferred catalysts thanks to its high activity and hydrothermal stability. Hydrothermal stability is related to dealumination, i.e. removal of aluminum from the zeolite framework to form extraframework aluminum, at high temperatures in the presence of water vapor. Copperexchanged chabazite (Cu-CHA) zeolites have higher hydrothermal stability compared to H-chabazite (H-CHA). To understand the delayed dealumination of Cu-CHA catalysts, we have investigated the reaction paths for dealumination in H-CHA and Cu-CHA using density functional theory (DFT) calculations combined with microkinetic modeling. We find that Cu-CHA and H-CHA follow similar four-step hydrolysis processes, yet the dealumination of Cu-CHA has higher energy barriers, suggesting stabilization of the CHA structure by Cu ions. Furthermore, the preferred reaction product upon complete dealumination of Cu-CHA is a copper-aluminate like species bound to the zeolite framework. The microkinetic analysis quantifies the increased stability of Cu-CHA as compared to H-CHA. In addition to the high-temperature dealumination, we investigated the role of water on low-temperature SCR by experimentally measuring the activity and reaction order of water. The reaction order of water is found to be increasingly negative with increasing water pressure. DFT calculations reveal that water blocks the active Cu-sites and a DFT-based microkinetic model reproduces the measured change of reaction order with water pressure.
5.	Artemenko, A., et al. (författare) Reference XPS spectra of amino acids 2021 Konferensbidrag (refereegranskat)abstract In this report we present XPS data for five amino acids (AAs) (tryptophan, methionine, glutamine, glutamic acid, and arginine) with different side chain groups measured in solid state (powder form). The theoretically and experimentally obtained chemical structure of AAs are compared. Here, we analyse and discuss C 1 s, N 1 s, O 1s and S 2p core level binding energies, FWHMs, atomic concentrations of the functional groups in AAs. The experimentally obtained and theoretically calculated ratio of atomic concentrations are compared. The zwitterionic nature of methionine and glutamine in solid state was determined from protonated amino groups in N 1s peak and deprotonated carboxylic groups in the C 1s spectrum. The obtained XPS results for AAs well correspond with previously reported data.
6.	Barišić, Antun, et al. (författare) Experimental Data Contributing to the Elusive Surface Charge of Inert Materials in Contact with Aqueous Media 2021 Ingår i: Colloids and interfaces. - : MDPI. - 2504-5377. ; 5:1 Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract We studied the charging of inert surfaces (polytetrafluoroethylene, i.e., PTFE; graphite; graphene; and hydrophobic silica) using classical colloid chemistry approaches. Potentiometric titrations showed that these surfaces acquired less charge from proton-related reactions than oxide minerals. The data from batch-type titrations for PTFE powder did not show an effect of ionic strength, which was also in contrast with results for classical colloids. In agreement with classical colloids, the electrokinetic results for inert surfaces showed the typical salt level dependence. In some cases, the point of zero net proton charge as determined from mass and tentatively from acid–base titration differed from isoelectric points, which has also been previously observed, for example by Chibowski and co-workers for ice electrolyte interfaces. Finally, we found no evidence for surface contaminations of our PTFE particles before and after immersion in aqueous solutions. Only in the presence of NaCl-containing solutions did cryo-XPS detect oxygen from water. We believe that our low isoelectric points for PTFE were not due to impurities. Moreover, the measured buffering at pH 3 could not be explained by sub-micromolar concentrations of contaminants. The most comprehensive explanation for the various sets of data is that hydroxide ion accumulation occurred at the interfaces between inert surfaces and aqueous solutions.
7.	Asfaw, Habtom Desta, Dr. 1986-, et al. (författare) Facile synthesis of hard carbon microspheres from polyphenols for sodium-ion batteries : insight into local structure and interfacial kinetics 2020 Ingår i: Materials Today Energy. - : Elsevier BV. - 2468-6069. ; 18 Tidskriftsartikel (refereegranskat)abstract Hard carbons are the most promising negative active materials for sodium ion storage. In this work, a simple synthesis approach is proposed to produce hard carbon microspheres (CMSs) (with a mean diameter of ~1.3 μm) from resorcinol-formaldehyde precursors produced via acid-catalyzed polycondensation reaction. Samples prepared at 1200, 1400, and 1500 oC showed different electrochemical behavior in terms of reversible capacity, initial coulombic efficiency (iCE), and the mechanism of sodium ion storage. The specific capacity contributions from the flat voltage profile (<0.1 V) and the sloping voltage region (0.1–1 V) showed strong correlation to the local structure (and carbonization temperature) determined by the interlayer spacing (d002) and the Raman ID/IG ratio of the hard carbons (HCs) and the rate of cycling. Electrochemical tests indicated that the HC synthesized at 1500 oC performed best with an iCE of 85–89% and a reversible capacity of 300–340 mAh g−1 at 10 mA g−1, with the majority of charge stored below 0.1 V. The d002 and the ID/IG ratio for the sample were ~3.7 Å and ~1.27, respectively, parameters indicative of the ideal local structure in HCs required for optimum performance in sodium-ion cells. In addition, galvanostatic tests on three-electrode half-cells cells revealed that sodium metal plating occurred as cycling rates were increased beyond 80 mA g−1 leading to considerably high capacity and poor coulombic efficiency, a point that must be considered in full-cell batteries. Pairing the hard CMS electrodes with Prussian white positive electrode, a proof-of-concept cell could provide a specific capacity of almost 100 mAh g−1 maintained for more than 50 cycles with a nominal voltage of 3 V.
8.	Banerjee, Ambar, 1985-, et al. (författare) Accessing metal-specific orbital interactions in C–H activation with resonant inelastic X-ray scattering 2024 Ingår i: Chemical Science. - : Royal Society of Chemistry. - 2041-6520 .- 2041-6539. ; 15:7, s. 2398-2409 Tidskriftsartikel (refereegranskat)abstract Photochemically prepared transition-metal complexes are known to be effective at cleaving the strong C–H bonds of organic molecules in room temperature solutions. There is also ample theoretical evidence that the two-way, metal to ligand (MLCT) and ligand to metal (LMCT), charge-transfer between an incoming alkane C–H group and the transition metal is the decisive interaction in the C–H activation reaction. What is missing, however, are experimental methods to directly probe these interactions in order to reveal what determines reactivity of intermediates and the rate of the reaction. Here, using quantum chemical simulations we predict and propose future time-resolved valence-to-core resonant inelastic X-ray scattering (VtC-RIXS) experiments at the transition metal L-edge as a method to provide a full account of the evolution of metal–alkane interactions during transition-metal mediated C–H activation reactions. For the model system cyclopentadienyl rhodium dicarbonyl (CpRh(CO)2), we demonstrate, by simulating the VtC-RIXS signatures of key intermediates in the C–H activation pathway, how the Rh-centered valence-excited states accessible through VtC-RIXS directly reflect changes in donation and back-donation between the alkane C–H group and the transition metal as the reaction proceeds via those intermediates. We benchmark and validate our quantum chemical simulations against experimental steady-state measurements of CpRh(CO)2 and Rh(acac)(CO)2 (where acac is acetylacetonate). Our study constitutes the first step towards establishing VtC-RIXS as a new experimental observable for probing reactivity of C–H activation reactions. More generally, the study further motivates the use of time-resolved VtC-RIXS to follow the valence electronic structure evolution along photochemical, photoinitiated and photocatalytic reactions with transition metal complexes.
9.	Brülls, Steffen, 1991, et al. (författare) Bonding between π-Conjugated Polycations and Monolayer Graphene: Decisive Role of Anions 2023 Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 127:4, s. 1917-28 Tidskriftsartikel (refereegranskat)abstract Functionalization and precise modulation of the electronic properties of graphene are key processes in the development of new applications of this promising material. This study examines the potential of using organic polycations as p-dopants and/or anchoring motifs for non-covalent functionalization. A library of hybrid materials was prepared through wet-chemical non-covalent functionalization. Both chemical vapor deposition graphene and reduced graphene oxide were functionalized with a series of neutral and polycationic benzimidazole-based systems. We report on how both the number of anions and the size, shape, and magnitude of the positive charge of the benzimidazole-based systems cooperatively affect the redox properties as well as the affinity for and the nature of bonding to graphene. The redox properties of the benzimidazole-based systems were studied by cyclic voltammetry. The functionalized graphene materials were characterized by Raman spectroscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry. Density functional theory calculations were performed to make contact between the experimental results obtained for molecular samples and hybrid materials. No universal dependence of the binding affinity on a single parameter, such as the amount of positive charge or the size of the system, was found. Instead, the cooperative effect of the three-dimensional structure of the benzimidazole-based systems and the number of anions was found to play a pivotal role. Together, these parameters determine the degree of partial electron sharing and magnitude of dispersion forces involved in the binding of members of this family of benzimidazole-based systems to graphene.
10.	Kamlar, Martin, 1981, et al. (författare) Polycyclizations of Ketoesters: Synthesis of Complex Tricycles with up to Five Stereogenic Centers from Available Starting Materials 2020 Ingår i: Organic Letters. - : American Chemical Society (ACS). - 1523-7052 .- 1523-7060. ; 22:21, s. 8387-8391 Tidskriftsartikel (refereegranskat)abstract Here we present a polycyclization of oxotriphenylhexanoates. The polycyclization is governed by electronic effects, and three major synthetic paths have been established leading to stereochemically complex tricyclic frameworks with up to five stereogenic centers. The method is compatible with an array of functional groups, allowing pharmacophoric elements to be introduced post cyclization.
11.	Renier, Olivier, et al. (författare) Shape Preserving Single Crystal to Amorphous to Single Crystal Polymorphic Transformation Is Possible 2021 Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 143:48, s. 20202-20206 Tidskriftsartikel (refereegranskat)abstract Many crystalline materials form polymorphs and undergo solid–solid transitions between different forms as a function of temperature or pressure. However, there is still a poor understanding of the mechanism of transformation. Conclusions about the transformation process are typically drawn by comparing the crystal structures before and after the conversion, but gaining detailed mechanistic knowledge is strongly impeded by the generally fast rate of these transitions. When the crystal morphology does not change, it is assumed that crystallinity is maintained throughout the process. Here we report transformation between polymorphs of ZnCl2(1,3-diethylimidazole-2-thione)2 which are sufficiently slow to allow unambiguous assignment of single crystal to single crystal transformation with shape preservation proceeding through an amorphous intermediate phase. This result fundamentally challenges the commonly accepted views of polymorphic phase transition mechanisms.
12.	Wiberg, Cedrik, 1989, et al. (författare) The electrochemical response of core-functionalized naphthalene Diimides (NDI) – a combined computational and experimental investigation 2021 Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 367 Tidskriftsartikel (refereegranskat)abstract © 2020 Aqueous organic redox flow batteries (AORFBs) have attracted increased interest as sustainable energy storage devices due to the desire of increasing electricity production from renewable energy sources. Several organic systems have been tested as redox active systems in AORFBs but few fundamental electrochemical studies exist. This article provides reduction potentials and acid constants, pKa, of nine different core-substituted naphthalene diimides (NDI), calculated using density functional theory (DFT). Reduction potentials were acquired at each oxidation state for the nine species and were used to achieve a correlation between the electron donating ability of the substituents and the potential. Cyclic voltammograms were simulated using the scheme-of-squares framework to include both electron and proton transfer processes. The results show that the anion radical is unprotonated in the entire pH range, while the dianion can be protonated in one or two steps depending on the substituent. The core substituents may also have acid-base properties. and optimization of the redox properties for battery applications can therefore be obtained both by changing the core substituent and by changing pH of the electrolyte. Three core-substituted NDI molecules were studied experimentally and good qualitative agreement with the theoretically predicted behaviour was demonstrated. For 2,6-di(dimethylamino)-naphthalene diimide (2DMA-NDI), the calculations showed that one of the DMA substituents could be protonated in the accessible pH range and pKa was determined to 3.95 using 1H NMR spectroscopy. The redox mechanism of each molecule was explored and the qualitative agreement between theory and experiment clearly shows that this combination provides a better understanding of the systems and offers opportunities for further developments. The applicability of NDI for redox flow batteries is finally discussed.
13.	Yang, Yizhou, 1992, et al. (författare) A self-standing three-dimensional covalent organic framework film 2023 Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 14:1 Tidskriftsartikel (refereegranskat)abstract Covalent crystals such as diamonds are a class of fascinating materials that are challenging to fabricate in the form of thin films. This is because spatial kinetic control of bond formation is required to create covalently bonded crystal films. Directional crystal growth is commonly achieved by chemical vapor deposition, an approach that is hampered by technical complexity and associated high cost. Here we report on a liquid-liquid interfacial approach based on physical-organic considerations to synthesize an ultrathin covalent crystal film. By distributing reactants into separate phases using hydrophobicity, the chemical reaction is confined to an interface that orients the crystal growth. A molecular-smooth interface combined with in-plane isotropic conditions enables the synthesis of films on a centimeter size scale with a uniform thickness of 13 nm. The film exhibits considerable mechanical robustness enabling a free-standing length of 37 µm, as well as a clearly anisotropic chemical structure and crystal lattice alignment.
14.	Zhang, Chu, et al. (författare) Steps and catalytic reactions : CO oxidation with preadsorbed O on Rh(553) 2022 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 715 Tidskriftsartikel (refereegranskat)abstract Industrial catalysts are often comprised of nanoparticles supported on high-surface-area oxides, in order to maximise the catalytically active surface area and thereby utilise the active material better. These nanoparticles expose steps and corners that, due to low coordination to neighboring atoms, are more reactive and, as a consequence, are often assumed to have higher catalytic activity. We have investigated the reaction between CO and preadsorbed O on a stepped Rh(553) surface, and show that CO oxidation indeed occurs faster than on the flat Rh(111) surface at the same temperature. However, we do find that this is not a result of reactions at the step sites but rather at the terrace sites close to the steps, due to in-plane relaxation enabled by the step. This insight can provide ways to optimize the shape of the nanoparticles to further improve the activity of certain reactions.
15.	Amombo Noa, Francoise Mystere, 1988, et al. (författare) 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 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.
16.	Li, Zhuofeng, 1991-, et al. (författare) Tuning morphology, composition and oxygen reduction reaction (ORR) catalytic performance of manganese oxide particles fabricated by γ-radiation induced synthesis 2021 Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 583, s. 71-79 Tidskriftsartikel (refereegranskat)abstract A γ-radiation induced synthesis method is used to fabricate manganese oxide catalysts through both reduction and oxidation routes. It is shown that the morphology, composition and electrochemical performance of the produced manganese oxide particles can be tuned by altering the redox conditions. The catalysts prepared via radiolytic oxidation have a hollow spherical morphology, possess γ-MnO2 structure and show high catalytic activity for the complete four-electron reaction pathway of the oxygen reduction reaction (ORR) in alkaline electrolyte. Meanwhile, the catalysts synthesized via radiolytic reduction possess a rod-like morphology with a Mn3O4 bulk structure and favour the incomplete two-electron reaction pathway for ORR. The high catalytic activity of the manganese oxide synthesized via the oxidation route can be attributed to high electrochemical surface area and increased amount of Mn3+ on the surface as compared to those in the sample obtained via the reduction route.
17.	Wang, Xuan, et al. (författare) Effects of Anthropogenic Chlorine on PM2.5 and Ozone Air Quality in China 2020 Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 54:16, s. 9908-9916 Tidskriftsartikel (refereegranskat)abstract China has large anthropogenic chlorine emissions from agricultural fires, residential biofuel, waste incineration, coal combustion, and industrial processes. Here we quantify the effects of chlorine on fine particulate matter (PM2.5) and ozone air quality across China by using the GEOS-Chem chemical transport model with comprehensive anthropogenic emissions and detailed representation of gas-phase and heterogeneous chlorine chemistry. Comparison of the model to observed ClNO2, HCl, and particulate Cl- concentrations shows that reactive chlorine in China is mainly anthropogenic, unlike in other continental regions where it is mostly of marine origin. The model is successful in reproducing observed concentrations and their distributions, lending confidence in the anthropogenic chlorine emission estimates and the resulting chemistry. We find that anthropogenic chlorine emissions increase total inorganic PM2.5 by as much as 3.2 μg m-3 on an annual mean basis through the formation of ammonium chloride, partly compensated by a decrease of nitrate because ClNO2 formation competes with N2O5 hydrolysis. Annual mean MDA8 surface ozone increases by up to 1.9 ppb, mainly from ClNO2 chemistry, while reactivities of volatile organic compounds increase (by up to 48% for ethane). We find that a sufficient representation of chlorine chemistry in air quality models can be obtained from consideration of HCl/Cl- thermodynamics and ClNO2 chemistry, because other more complicated aspects of chlorine chemistry have a relatively minor effect.
18.	Andersson Trojer, Markus, et al. (författare) Elastic strain-hardening and shear-thickening exhibited by thermoreversible physical hydrogels based on poly(alkylene oxide)-grafted hyaluronic acid or carboxymethylcellulose 2020 Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 22:26, s. 14579-14590 Tidskriftsartikel (refereegranskat)abstract The formation of strongly elastic physical gels based on poly(alkylene oxide)-grafted hyaluronan or carboxymethylcellulose, exhibiting both shear-thickening and strain-hardening have been studied using rheometry and explained using a slightly different interpretation of the transient network theory. The graft copolymers were prepared by a quantitative coupling reaction. Their aqueous solutions displayed a thermoreversible continuous transition from Newtonian fluid to viscoelastic solid which could be controlled by the reaction conditions. The evolution of all material properties of the gel could be categorized into two distinct temperature regimes with a fast evolution at low temperatures followed by a slow evolution at high temperatures. The activation energy of the zero shear viscosity and the relaxation time of the graft inside the interconnecting microdomains were almost identical to each other in both temperature regimes. This suggests that the number of microdomains remained approximately constant whereas the aggregation number inside the microdomains increased according to the binodal curve of the thermosensitive graft.
19.	Bjerregaard, Joachim, 1996, et al. (författare) Interpretation of H 2 -TPR from Cu-CHA Using First-Principles Calculations 2024 Ingår i: Journal of Physical Chemistry C. - 1932-7447 .- 1932-7455. ; 128:11, s. 4525-4534 Tidskriftsartikel (refereegranskat)abstract Temperature-programmed reduction and oxidation are used to obtain information on the presence and abundance of different species in complex catalytic materials. The interpretation of the temperature-programmed reaction profiles is, however, often challenging. One example is H2 temperature-programmed reduction (H2-TPR) of Cu-chabazite (Cu-CHA), which is a material used for ammonia assisted selective catalytic reduction of NOx (NH3-SCR). The TPR profiles of Cu-CHA consist generally of three main peaks. A peak at 220 °C is commonly assigned to ZCuOH, whereas peaks at 360 and 500 °C generally are assigned to Z2Cu, where Z represents an Al site. Here, we analyze H2-TPR over Cu-CHA by density functional theory calculations, microkinetic modeling, and TPR measurements of samples pretreated to have a dominant Cu species. We find that H2 can react with Cu ions in oxidation state +2, whereas adsorption on Cu ions in +1 is endothermic. Kinetic modeling of the TPR profiles suggests that the 220 °C peak can be assigned to Z2CuOCu and ZCuOH, whereas the peaks at higher temperatures can be assigned to paired Z2Cu and Z2CuHOOHCu species (360 °C) or paired Z2Cu and Z2CuOOCu (500 °C). The results are in good agreement with the experiments and facilitate the interpretation of future TPR experiments.
20.	Feng, Yingxin, 1994 (författare) Reaction kinetics of NH3-SCR over Cu-CHA from first principles 2024 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Ammonia-assisted selective catalytic reduction (NH3-SCR) is an advanced technology to reduce nitrogen oxide (NOx) emissions from lean-burn engines. NH3 is added to the exhaust gas and reacts selectively with NOx, forming N2 and H2O. Small-pore Cu-exchanged chabazite (Cu-CHA) is a widely used zeolite-based catalyst for NH3-SCR thanks to its high activity, high selectivity, and durability. However, one issue is the formation of small amounts of nitrous oxide (N2O), which is a strong greenhouse gas. Atomic level understanding is valuable to improve the performance of NH3-SCR catalyst and meet the increasingly stringent emission standards. The state of Cu-CHA during NH3-SCR reaction depends sensitively on the reaction temperature. At low temperatures, Cu-ions are solvated by NH3, forming Cu[(NH3)2]+ complexes, while framework-bound Cu dominates at high temperatures. Experimentally, a non-monotonic behavior in NO conversion is observed with increasing temperature, which reflects a change in the active site. In this thesis, NH3-SCR over Cu-CHA is investigated using density functional theory (DFT) calculations and kinetic simulations. In the low-temperature range (<250℃), a pair of Cu[(NH3)2]+ is required for O2 adsorption to form a Cu-peroxo complex, which is a key Cu-intermediate. The reaction intermediates HONO and H2NNO can be converted to N2 and H2O over Brønsted acid sites. H2NNO is found to be the origin of N2O formation when decomposing over Cu-peroxo species. At high-temperature (>350℃), the proposed reaction mechanism suggests that the reaction proceeds over single framework Cu sites and starts from the co-adsorption of O2 and NO. The main source of N2O formation at high temperatures is suggested to be ammonium nitrate decomposition. By combining the reaction mechanisms for high and low temperatures, the non-monotonic temperature-dependent reaction activity is successfully reproduced. The present work deepens the understanding of the reaction mechanism of NH3-SCR on Cu-CHA in a wide temperature range and provides theoretical support for further improvement of the catalyst performance.
21.	Gogoi, Neeha, et al. (författare) Silyl-Functionalized Electrolyte Additives and Their Reactivitytoward Lewis Bases in Li-Ion Cells br 2022 Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 1520-5002 .- 0897-4756. ; 34:8, s. 3831-3838 Tidskriftsartikel (refereegranskat)abstract Silyl groups are included in a wide range of electrolyteadditives to enhance the performance of state-of-the-art Li-ion batteries. Arecognized representative thereof is tris-(trimethylsilyl)phosphate(TMSPa) which, along with the similarly structured phosphite, has beenat the center of numerous electrolyte studies. Even though the silyl grouphas already been widely reported to be specifically reactive towardsfluorides, herein, a reactivity towards several Lewis bases typically found inLi-ion cells is postulated and investigated with the aim to establish a moresimplified and generally applicable reaction mechanism thereof. Bothgaseous and electrolyte soluble reactants and products are monitored bycombining nuclear magnetic resonance and injection cell-coupled massspectrometry. Experimental observations are supported by computationalmodels. The results clearly demonstrate that the silyl groups react withwater, hydroxide, and methoxide and thereby detach in a stepwise fashion from the central phosphate in TMSPa. Intermolecularinteraction between TMSPa and the reactants likely facilitates dissolution and lowers the free energy of reaction. Lewis bases are wellknown to trigger side reactions involving both the Li-ion electrode and electrolyte. By effectively scavenging these, the silyl group canbe explained to lower cell impedance and prolong the lifetime of modern Li-ion batteries.
22.	Nuri, Ayat, et al. (författare) Synthesis and Characterization of Palladium Supported Amino Functionalized Magnetic-MOF-MIL-101 as an Efficient and Recoverable Catalyst for Mizoroki–Heck Cross-Coupling 2020 Ingår i: Catalysis Letters. - : Springer. - 1011-372X .- 1572-879X. ; 150:9, s. 2617-2629 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.
23.	Pipertzis, Achilleas, 1992, et al. (författare) Ion transport, mechanical properties and relaxation dynamics in structural battery electrolytes consisting of an imidazolium protic ionic liquid confined into a methacrylate polymer 2023 Ingår i: Energy Materials: Materials Science and Engineering for Energy Systems. - 1748-9237. ; 3 Tidskriftsartikel (refereegranskat)abstract The effect of confining a liquid electrolyte into a polymer matrix was studied by means of Raman spectroscopy, differential scanning calorimetry, temperature-modulated differential scanning calorimetry, dielectric spectroscopy, and rheology. The polymer matrix was obtained from thermal curing ethoxylated bisphenol A dimethacrylate while the liquid electrolyte consisted of a protic ionic liquid based on the ethyl-imidazolium cation [C2HIm] and the bis(trifluoromethanesulfonyl)imide [TFSI] anion, doped with LiTFSI salt. We report that the confined liquid phase exhibits the following characteristics: (i) a distinctly reduced degree of crystallinity; (ii) a broader distribution of relaxation times; (iii) reduced dielectric strength; (iv) a reduced cooperativity length scale at the liquid-to-glass transition temperature (Tg); and (v) up-speeded local Tg-related ion dynamics. The latter is indicative of weak interfacial interactions between the two nanophases and a strong geometrical confinement effect, which dictates both the ion dynamics and the coupled structural relaxation, hence lowering Tg by about 4 K. We also find that at room temperature, the ionic conductivity of the structural electrolyte achieves a value of 0.13 mS/cm, one decade lower than the corresponding bulk electrolyte. Three mobile ions (Im+, TFSI-, and Li+) contribute to the measured ionic conductivity, implicitly reducing the Li+ transference number. In addition, we report that the investigated solid polymer electrolytes exhibit the shear modulus needed for transferring the mechanical load to the carbon fibers in a structural battery. Based on these findings, we conclude that optimized microphase-separated polymer electrolytes, including a protic ionic liquid, are promising for the development of novel multifunctional electrolytes for use in future structural batteries.
24.	Prakash, Om, et al. (författare) How Rigidity and Conjugation of Bidentate Ligands Affect the Geometry and Photophysics of Iron N-Heterocyclic Complexes : A Comparative Study 2024 Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 63:10, s. 4461-4473 Tidskriftsartikel (refereegranskat)abstract Two iron complexes featuring the bidentate, nonconjugated N-heterocyclic carbene (NHC) 1,1′-methylenebis(3-methylimidazol-2-ylidene) (mbmi) ligand, where the two NHC moieties are separated by a methylene bridge, have been synthesized to exploit the combined influence of geometric and electronic effects on the ground- and excited-state properties of homoleptic FeIII-hexa-NHC [Fe(mbmi)3](PF6)3 and heteroleptic FeII-tetra-NHC [Fe(mbmi)2(bpy)](PF6)2 (bpy = 2,2′-bipyridine) complexes. They are compared to the reported FeIII-hexa-NHC [Fe(btz)3](PF6)3 and FeII-tetra-NHC [Fe(btz)2(bpy)](PF6)2 complexes containing the conjugated, bidentate mesoionic NHC ligand 3,3′-dimethyl-1,1′-bis(p-tolyl)-4,4′-bis(1,2,3-triazol-5-ylidene) (btz). The observed geometries of [Fe(mbmi)3](PF6)3 and [Fe(mbmi)2(bpy)](PF6)2 are evaluated through L-Fe-L bond angles and ligand planarity and compared to those of [Fe(btz)3](PF6)3 and [Fe(btz)2(bpy)](PF6)2. The FeII/FeIII redox couples of [Fe(mbmi)3](PF6)3 (−0.38 V) and [Fe(mbmi)2(bpy)](PF6)2 (−0.057 V, both vs Fc+/0) are less reducing than [Fe(btz)3](PF6)3 and [Fe(btz)2(bpy)](PF6)2. The two complexes show intense absorption bands in the visible region: [Fe(mbmi)3](PF6)3 at 502 nm (ligand-to-metal charge transfer, 2LMCT) and [Fe(mbmi)2(bpy)](PF6)2 at 410 and 616 nm (metal-to-ligand charge transfer, 3MLCT). Lifetimes of 57.3 ps (2LMCT) for [Fe(mbmi)3](PF6)3 and 7.6 ps (3MLCT) for [Fe(mbmi)2(bpy)](PF6)2 were probed and are somewhat shorter than those for [Fe(btz)3](PF6)3 and [Fe(btz)2(bpy)](PF6)2. [Fe(mbmi)3](PF6)3 exhibits photoluminescence at 686 nm (2LMCT) in acetonitrile at room temperature with a quantum yield of (1.2 ± 0.1) × 10-4, compared to (3 ± 0.5)
25.	Shukla, Shashi Kant, 1983-, et al. (författare) Melting point of ionic liquids 2020 Ingår i: Encyclopedia of ionic liquids. - Singapore : Springer. - 9789811067396 ; , s. 1-9 Bokkapitel (övrigt vetenskapligt/konstnärligt)
26.	Spiliopoulos, Panagiotis, 1987, et al. (författare) Cellulose modified to host functionalities via facile cation exchange approach 2024 Ingår i: Carbohydrate Polymers. - 0144-8617. ; 332 Tidskriftsartikel (refereegranskat)abstract Properties of cellulose are typically functionalized by organic chemistry means. We progress an alternative facile way to functionalize cellulose by functional group counter-cation exchange. While ion-exchange is established for cellulose, it is far from exploited and understood beyond the most common cation, sodium. We build on our work that established the cation exchange for go-to alkali metal cations. We expand and further demonstrate the introduction of functional cations, namely, lanthanides. We show that cellulose nanocrystals (CNCs) carrying sulfate-half ester groups can acquire properties through the counter-cation exchange. Trivalent lanthanide cations europium (Eu3+), dysprosium (Dy3+) and gadolinium (Gd3+) were employed. The respective ions showed distinct differences in their ability of being coordinated by the sulfate groups; with Eu3+fully saturating the sulfate groups while for Gd3+ and Dy3+, values of 82 and 41 % were determined by compositional analysis. CNCs functionalized with Eu3+ displayed red emission, those containing Dy3+ exhibited no optical functionality, while those with Gd3+revealed significantly altered magnetic relaxation times. Using cation exchange to alter cellulose properties in various ways is a tremendous opportunity for modification of the abundant cellulose raw materials for a renewable future.
27.	Yang, Yi, et al. (författare) Using an ionomer as a size regulator in γ-radiation induced synthesis of Ag nanocatalysts for oxygen reduction reaction in alkaline solution 2023 Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 646, s. 381-390 Tidskriftsartikel (refereegranskat)abstract Ag nanoparticles (Ag NPs) are among the most promising candidates to replace Pt as the catalyst for the oxygen reduction reaction (ORR) in anion exchange membrane fuel cells (AEMFCs). However, synthesizing size-controlled Ag NPs with efficient catalytic performance is still challenging. Herein, uniform Ag NPs are produced through a γ-radiation induced synthesis route in aqueous solutions, using the ionomer PTPipQ100 as both an efficient size regulator in the synthesis and a conductor of hydroxide ions during the ORR process. The origin of the size control is mainly attributed to the affinity of the ionomer to metallic silver. The resulting Ag NPs covered with ionomer layers can be applied as model catalysts for ORR. The nanoparticles that were prepared using 320 ppm ionomer in the reaction solution turned out to be coated with a ∼1 nm thick ionomer layer and exhibited superior ORR activity as compared to other Ag NPs of similar size studied here. The improved electrocatalytic performance can be attributed to the optimal ionomer coverage that enables fast oxygen diffusion, as well as interactions at the Ag-ionomer interface which promote the desorption of OH intermediates from the Ag surface. This work demonstrates the advantage of using an ionomer as the capping agent to produce efficient ORR catalysts.
28.	Iurchenkova, Anna A., 1997-, et al. (författare) MWCNT buckypaper/polypyrrole nanocomposites for supercapasitor application 2020 Ingår i: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 335 Tidskriftsartikel (refereegranskat)abstract In this work MWNT/polypyrrole nanocomposites were synthesized and investigated as electrode materials for supercapasitor application. The MWNT were synthesized by CCVD-method and precipitated as buckypaper film (NTBP). The polypyrrole was precipitated on the NTBP surface by chemical (sample NTBP_PPy_Chem) and electrochemical (sample NTBP_PPy_Elect) polymerization. The morphology and functional composition of individual and hybrid materials were investigated by microscopic and spectroscopic methods. It was obtained that the deposition method and presence of NTBP affects the polymer morphology. It was shown that PPy chemical deposition leads to the precipitation of a large amount of an amorphous polymer on a buckypaper surface. At the same time electrochemical deposition method promotes the synthesis of uniform polymer layers. In the second case, the mass of the precipitated polymer is smaller. It was found that both deposition methods are suitable for the polypyrrole deposition and can increase the buckypaper capacity almost twice. The material long cycling showed that the NTBP_PPy_Elect sample has the greatest stability. Thus, in this study, the relationship between morphology, functional composition and electrochemical properties of materials was studied. It was shown that the synthesis method allows controlling the morphology and/or functional composition of the materials. Also it was demonstrated that the synthesized structures are promising for use as supercapacitor electrodes due to the high specific capacitance and stability.
29.	Khokarale, Santosh G., et al. (författare) One-Pot, Metal-Free Synthesis of Dimethyl Carbonate from CO2 at Room Temperature 2020 Ingår i: Sustainable Chemistry. - : MDPI. - 2673-4079. ; 1:3, s. 298-314 Tidskriftsartikel (refereegranskat)abstract Herein, we report on the metal-free, one-pot synthesis of industrially important dimethyl carbonate (DMC) from molecular CO2 under ambient conditions. In this process, initially the CO2 was chemisorbed through the formation of a switchable ionic liquid (SIL), [DBUH] [CH3CO3], by the interaction of CO2 with an equivalent mixture of organic superbase 1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU) and methanol. The obtained SIL further reacted with methyl iodide (CH3I) to form DMC. The synthesis was carried out in both dimethyl sulfoxide (DMSO) and methanol. Methanol is preferred, as it not only served as a reagent and solvent in CO2 capture and DMC synthesis, but it also assisted in controlling the side reactions between chemical species such as CH3I and [DBUH]+ cation and increased the yield of DMC. Hence, the use of methanol avoided the loss of captured CO2 and favored the formation of DMC with high selectivity. Under the applied reaction conditions, 89% of the captured CO2 was converted to DMC. DBU was obtained, achieving 86% recovery of its salts formed during the synthesis. Most importantly, in this report we describe a simple and renewable solvent-based process for a metal-free approach to DMC synthesis under industrially feasible reaction conditions.
30.	Mousavinejad, Atiyeh, et al. (författare) Nickel-Based Metal–Organic Frameworks to Improve the CO2/CH4 Separation Capability of Thin-Film Pebax Membranes 2020 Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 59:28, s. 12834-12844 Tidskriftsartikel (refereegranskat)abstract Incorporating metal–organic frameworks (MOFs) into the thin layer of thin-film composite (TFC) membranes is an effective way of improving the CO2/CH4 separation performance. In this study, porous polyethersulfone (PES) membranes were surface-coated with a novel CO2-permeable layer consisting of CO2-philic Pebax and nickel-based MOF particles. The MOF particles were synthesized using nickel(II) acetate tetrahydrate as a metal source and 2-amino-1,4-dicarboxybenzene (NH2-BDC) as an organic linker. The properties and performance of the MOFs and synthesized membranes were assessed using analytical techniques including differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), field-emission scanning electron microscopy (FE-SEM), and dynamic light scattering (DLS). DLS analysis showed that the MOF particle size range was in a range of 350–650 nm. Moreover, cross-sectional FE-SEM images depicted that a uniform and dense Pebax layer was shaped on top of the PES substrate. Well dispersion of the particles was demonstrated by surface FE-SEM imaging. DSC analysis showed that embedding Ni-NH2-BDC MOF particles into the Pebax-1657 film increased the crystallinity degree and the glass-transition temperature (Tg) of resulted membranes. To evaluate the membrane’s separation performance, permeation experiments were performed with CO2, CH4, and CO2/CH4 mixtures at ambient temperature. Embedding 5 wt % Ni-based MOF particles improved the CO2 permeability and CO2/CH4 selectivity from 19.05 Barrer and 32.2 to 31.55 Barrer and 94, respectively, compared to MOF-free membranes. Loading MOF particles into the Pebax matrix also improved the real gas separation factor. The obtained results demonstrate the great potential of the fabricated TFC membranes for gas separation.
31.	Škvarla, Jiří, et al. (författare) Cryo-XPS : A new technique for the quantitative analysis of the structure of electric double layer at colloidal particles? 2020 Ingår i: Colloids and Surfaces A. - : Elsevier. - 0927-7757 .- 1873-4359. ; 586 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.
32.	Vucetic, Nemanja, et al. (författare) Tuned Bis-Layered Supported Ionic Liquid Catalyst (SILCA) for Competitive Activity in the Heck Reaction of Iodobenzene and Butyl Acrylate 2020 Ingår i: Catalysts. - : MDPI. - 2073-4344. ; 10:9 Tidskriftsartikel (refereegranskat)abstract A thorough experimental optimization of supported ionic liquid catalyst (SILCA) was performed in order to obtain a stable and efficient catalyst for the Heck reaction. Out of fifteen proposed structures, propyl imidazolium bromide-tetramethylguanidinium pentanoate modified SiO2 loaded with PdCl2 appeared to be the most stable and to have a good activity in the reaction between butylacrylate and iodobezene, resulting in a complete conversion in 40 min at 100 °C, in four consecutive experiments. This study elucidated on the stability of the catalytic system with an ionic liquid layer during the catalyst synthesis but also under reaction conditions. In the bis-layered catalyst, the imidazolium moiety as a part of internal layer, brought rigidity to the structure, while in external layer pentanoic acid gave sufficiently acidic carboxylic group capable to coordinate 1,1,3,3-tetramethylguanidine (TMG) and thus, allow good dispersion of Pd nanoparticles. The catalyst was characterized by means of XPS, FT-IR, TEM, ICP-OES, ζ-potential, EDX, TGA, and 13C NMR. The release and catch mechanism was observed, whereas Pd re-deposition can be hindered by catalyst poisoning and eventual loss of palladium.
33.	Yun, Jingwei, et al. (författare) Surface Composition Dependence on the Ice Nucleating Ability of Potassium-Rich Feldspar 2020 Ingår i: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 4:6, s. 873-881 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.
34.	Amombo Noa, Francoise Mystere, 1988, et al. (författare) Chiral Lanthanum Metal-Organic Framework with Gated CO2 Sorption and Concerted Framework Flexibility br 2022 Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 144:19, s. 8725-8733 Tidskriftsartikel (refereegranskat)abstract A metal-organic framework (MOF)CTH-17based on lanthanum-(III) and the conformationally chiral linker 1,2,3,4,5,6-hexakis(4-carboxyphenyl)-benzene, cpb6-: [La2(cpb)]middot1.5dmf was prepared by the solvothermal method indimethylformamide (dmf) and characterized by variable-temperature X-raypowder diffraction (VTPXRD), variable-temperature X-ray single-crystal diffrac-tion (SCXRD), and thermogravimetric analysis (TGA).CTH-17is a rod-MOFwith new topologyoch. It has high-temperature stability with Sohncke spacegroupsP6122/P6522 at 90 K andP622 at 300 and 500 K, all phases characterizedwith SCXRD and at 293 K also with three-dimensional (3D) electron diffraction. VTPXRD indicates a third phase appearing after620 K and stable up to 770 K. Gas sorption isotherms with N2indicate a modest surface area of 231 m2g-1forCTH-17, roughly inagreement with the crystal structure. Carbon dioxide sorption reveals a gate-opening effect ofCTH-17where the structure opens upwhen the loading of CO2reaches approximately similar to 0.45 mmol g-1or 1 molecule per unit cell. Based on the SCXRD data, this isinterpreted asflexibility based on the concerted movements of the propeller-like hexatopic cpb linkers, the movementintramolecularly transmitted by the pi-pi stacking of the cpb linkers and helped by thefluidity of the LaO6coordination sphere. Thiswas corroborated by density functional theory (DFT) calculations yielding the chiral phase (P622) as the energy minimum and acompletely racemic phase (P6/mmm), with symmetric cpb linkers representing a saddle point in a racemization process
35.	Andersson, Mikael, et al. (författare) Interplay between the Reorientational Dynamics of the B3H8- Anion and the Structure in KB3H8 2021 Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 125:7, s. 3716-3724 Tidskriftsartikel (refereegranskat)abstract The structure and reorientational dynamics of KB3H8 were studied by using quasielastic and inelastic neutron scattering, Raman spectroscopy, first-principles calculations, differential scanning calorimetry, and in situ synchrotron radiation powder X-ray diffraction. The results reveal the existence of a previously unknown polymorph in between the alpha'- and beta-polymorphs. Furthermore, it was found that the [B3H8](-) anion undergoes different reorientational motions in the three polymorphs alpha, alpha', and beta. In alpha-KB3H8, the [B3H8](-) anion performs 3-fold rotations in the plane created by the three boron atoms, which changes to a 2-fold rotation around the C-2 symmetry axis of the [B3H8](-) anion upon transitioning to alpha'-KB3H8. After transitioning to beta-KB3H8, the [B3H8](-) anion performs 4-fold rotations in the plane created by the three boron atoms, which indicates that the local structure of beta-KB3H8 deviates from the global cubic NaCl-type structure. The results also indicate that the high reorientational mobility of the [B3H8](-) anion facilitates the K+ cation conductivity, since the 2-orders-of-magnitude increase in the anion reorientational mobility observed between 297 and 311 K coincides with a large increase in K+ conductivity.
36.	Andersson, Mikael, 1988, et al. (författare) Interplay of NH4+ and BH4- reorientational dynamics in NH4BH4 2020 Ingår i: Physical Review Materials. - 2475-9953. ; 4:8 Tidskriftsartikel (refereegranskat)abstract The reorientational dynamics of ammonium borohydride (NH4BH4) was studied using quasielastic neutron scattering in the temperature interval from 10 to 240 K, which covers both the dynamically ordered and disordered polymorphs of NH4BH4. In the low-temperature (50 K) ordered polymorph of NH4BH4, analysis of the quasielastic neutron scattering data reveals that no reorientational dynamics is present within the probed timescale region of 0.1 to 100 ps. In the high-temperature (50 K) disordered polymorph, the analysis establishes the onset of NH4+ and BH4- dynamics at around 50 and 125 K, respectively. The relaxation time at 150 K for NH4+ is approximately 1 ps, while around 100 ps for BH4- . The NH4+ dynamics at temperatures below 125 K is associated with preferential tetrahedral tumbling motions, where each of the hydrogen atoms in the NH4+ tetrahedron can visit any of the four hydrogen sites, however, reorientations around a specific axis are more frequently occurring (C-2 or C3). At higher temperatures, the analysis does not exclude a possible evolution of the NH4+ dynamics from tetrahedral tumbling to either cubic tumbling, where the hydrogen atoms can visit any of the eight positions corresponding to the corners of a cube, or isotropic rotational diffusion, where the hydrogen atoms can visit any location on the surface of a sphere. The BH4- dynamics can be described as cubic tumbling. The difference in reorientational dynamics between the two ions is related to the difference of the local environment where the dynamically much slower BH4- anion imposes a noncubic environment on the NH4+ cation.
37.	Axelsson, Anton, 1991, et al. (författare) Asymmetric Synthesis of Dihydropyranones with Three Contiguous Stereocenters by an NHC-Catalyzed Kinetic Resolution 2021 Ingår i: European Journal of Organic Chemistry. - : Wiley. - 1434-193X .- 1099-0690. ; 2021:25, s. 3657-3661 Tidskriftsartikel (refereegranskat)abstract An oxidative NHC-catalyzed kinetic resolution (KR) of racemic mixtures is presented. The developed reaction furnishes tricyclic dihydropyranones with three contiguous stereocenters in excellent dia- and enantioselectivity, with good-to-moderate yields. Mechanistic studies indicate that the rate-determining step of the reaction is the formation of the Breslow intermediate, while the selectivity determining step occurs later in the mechanism. The presented methodology enables rapid synthesis of complex structures in a single step.
38.	B. Brant Carvalho, Paulo H., et al. (författare) Elucidating the guest disorder in structure II argon hydrate : A neutron diffraction isotopic substitution study 2020 Ingår i: Journal of Solid State Chemistry. - : Elsevier. - 0022-4596 .- 1095-726X. ; 285 Tidskriftsartikel (refereegranskat)abstract Clathrate hydrates with the cubic structure II (CS-II) form typically with large guest molecules, such as tetrahydrofuran, trimethylamine oxide, or propane. However, CS-II is also realized for argon hydrate despite the comparatively small van der Waals diameter of the guest (around 3.8 angstrom). Here, the structure of deuterated argon hydrate was studied at ambient pressure in the temperature range 20-95 K using neutron diffraction and comparing natural Ar with Ar-36, which scatters neutrons more than 13 times more efficiently. The procedure allowed to unambiguously establish the positional disorder within the large cages of CS-H, while simultaneously refining host and guest structures. These cages are singly occupied and off-centered argon atoms distribute on two tetrahedron-shaped split positions with a ratio 3:1. Molecular dynamics (MD) simulations revealed that the crystallographic positional disorder structure is due to mobile argon atoms even at 20 K. The MD potential energy distribution confirmed the diffraction model. It is noted that the unit cell volumes of argon hydrate in the investigated temperature range are virtually identical to N-2 hydrate, which has a similar composition at ambient pressure, indicating a very similar (slightly attractive) host-guest interaction.
39.	Busch, Michael, et al. (författare) How to Predict the p Ka of Any Compound in Any Solvent 2022 Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 7:20, s. 17369-17383 Tidskriftsartikel (refereegranskat)abstract Acid-base properties of molecules in nonaqueous solvents are of critical importance for almost all areas of chemistry. Despite this very high relevance, our knowledge is still mostly limited to the pKa of rather few compounds in the most common solvents, and a simple yet truly general computational procedure to predict pKa's of any compound in any solvent is still missing. In this contribution, we describe such a procedure. Our method requires only the experimental pKa of a reference compound in water and a few standard quantum-chemical calculations. This method is tested through computing the proton solvation energy in 39 solvents and by comparing the pKa of 142 simple compounds in 12 solvents. Our computations indicate that the method to compute the proton solvation energy is robust with respect to the detailed computational setup and the construction of the solvation model. The unscaled pKa's computed using an implicit solvation model on the other hand differ significantly from the experimental data. These differences are partly associated with the poor quality of the experimental data and the well-known shortcomings of implicit solvation models. General linear scaling relationships to correct this error are suggested for protic and aprotic media. Using these relationships, the deviations between experiment and computations drop to a level comparable to that observed in water, which highlights the efficiency of our method.
40.	Carmona, Pierre, 1995, et al. (författare) Cross-sectional structure evolution of phase-separated spin-coated ethylcellulose/hydroxypropylcellulose films during solvent quenching 2022 Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 12:40, s. 26078-26089 Tidskriftsartikel (refereegranskat)abstract Porous phase-separated ethylcellulose/hydroxypropylcellulose (EC/HPC) films are used to control drug transport out of pharmaceutical pellets. The films are applied on the pellets using fluidized bed spraying. The drug transport rate is determined by the structure of the porous films that are formed as the water-soluble HPC leaches out. However, a detailed understanding of the evolution of the phase-separated structure during production is lacking. Here, we have investigated EC/HPC films produced by spin-coating, which mimics the industrial manufacturing process. This work aimed to understand the structure formation and film shrinkage during solvent evaporation. The cross-sectional structure evolution was characterized using confocal laser scanning microscopy (CLSM), profilometry and image analysis. The effect of the EC/HPC ratio on the cross-sectional structure evolution was investigated. During shrinkage of the film, the phase-separated structure undergoes a transition from 3D to nearly 2D structure evolution along the surface. This transition appears when the typical length scale of the phase-separated structure is on the order of the thickness of the film. This was particularly pronounced for the bicontinuous systems. The shrinkage rate was found to be independent of the EC/HPC ratio, while the initial and final film thickness increased with increasing HPC fraction. A new method to estimate part of the binodal curve in the ternary phase diagram for EC/HPC in ethanol has been developed. The findings of this work provide a good understanding of the mechanisms responsible for the morphology development and allow tailoring of thin EC/HPC films structure for controlled drug release.
41.	Cedervall, Johan, et al. (författare) Phase stability and structural transitions in compositionally complex LnMO 3 perovskites 2021 Ingår i: Journal of Solid State Chemistry. - : Elsevier BV. - 0022-4596 .- 1095-726X. ; 300 Tidskriftsartikel (refereegranskat)abstract Entropy stabilised materials have possibilities for tailoring functionalities to overcome challenges in materials science. The concept of configurational entropy can also be applied to metal oxides, but it is unclear whether these could be considered as solid solutions in the case of perovskite-structured oxides and if the configurational entropy plays a stabilising role. In this study, compositionally complex perovskite oxides, LnMO3 (Ln = La, Nd, Sm, Ca and Sr, M = Ti, Cr, Mn, Fe, Co, Ni, and Cu), are investigated for their phase stability and magnetic behaviour. Phase-pure samples were synthesised, and the room temperature structures were found to crystallise in either Pnma or R3¯c space groups, depending on the composition and the resulting tolerance factor, while the structural transition temperatures correlate with the pseudo cubic unit cell volume. The techniques used included diffraction with X-rays and neutrons, both ex- and in-situ, X-ray photoelectron spectroscopy, magnetometry as well as electron microscopy. Neutron diffraction studies on one sample reveal that no oxygen vacancies are found in the structure and that the magnetic properties are ferrimagnetic-like with magnetic moments mainly coupled antiferromagnetically along the crystallographic c-direction. X-ray photoelectron spectroscopy gave indications of the oxidation states of the constituting ions where several mixed oxidation states are observed in these valence-compensated perovskites.
42.	Garcia-Martinez, Fernando, et al. (författare) Catalytic oxidation of CO on a curved Pt(111) surface : simultaneous ignition at all facets through a transient CO-O complex. 2020 Ingår i: Angewandte Chemie International Edition. - : John Wiley & Sons. - 1433-7851 .- 1521-3773. ; 59:45, s. 20037-20043 Tidskriftsartikel (refereegranskat)abstract The catalytic oxidation of carbon monoxide (CO) on transition metals, such as platinum (Pt), is commonly viewed as a sharp transition from the CO-inhibited surface to the active metal, covered with oxygen (O). However, we find that minor amounts of O are present in the CO-poisoned layer that explain why, surprisingly, CO desorbs at stepped and flat Pt crystal planes at once, regardless of the reaction conditions. Using near-ambient pressure X-ray photoemission and a curved Pt(111) crystal we probe the chemical composition at surfaces with variable step density during the CO oxidation reaction. The systematic analysis of carbon and oxygen core levels across the curved crystal reveals that, right before light-off, subsurface O builds up within (111) terraces. This is key to trigger the simultaneous ignition of the catalytic reaction at different Pt surfaces, as indicated by ab-initio theory: a CO-Pt-O complex is formed that equals the CO chemisorption energy at terraces and steps, leading to the abrupt desorption of poisoning CO from all crystal facets at the same temperature.
43.	Grammatico, Domenico, et al. (författare) Heterogenised Molecular Catalysts for Sustainable Electrochemical CO 2 Reduction 2022 Ingår i: Angewandte Chemie International Edition. - : John Wiley & Sons. - 1433-7851 .- 1521-3773. ; 61:38 Forskningsöversikt (refereegranskat)abstract There has been a rapid rise in interest regarding the advantages of support materials to protect and immobilise molecular catalysts for the carbon dioxide reduction reaction (CO2RR) in order to overcome the weaknesses of many well-known catalysts in terms of their stability and selectivity. In this Review, the state of the art of different catalyst-support systems for the CO2RR is discussed with the intention of leading towards standard benchmarking for comparison of such systems across the most relevant supports and immobilisation strategies, taking into account these multiple pertinent metrics, and also enabling clearer consideration of the necessary steps for further progress. The most promising support systems are described, along with a final note on the need for developing more advanced experimental and computational techniques to aid the rational design principles that are prerequisite to prospective industrial upscaling.
44.	Hamawandi, Bejan, PhD, et al. (författare) Composition Tuning of Nanostructured Binary Copper Selenides through Rapid Chemical Synthesis and their Thermoelectric Property Evaluation 2020 Ingår i: Nanomaterials. - : MDPI. - 2079-4991. ; 10:5 Tidskriftsartikel (refereegranskat)abstract Reduced energy consumption and environmentally friendly, abundant constituents are gaining more attention for the synthesis of energy materials. A rapid, highly scalable, and process-temperature-sensitive solution synthesis route is demonstrated for the fabrication of thermoelectric Cu2−xSe. The process relies on readily available precursors and microwave-assisted thermolysis, which is sensitive to reaction conditions; yielding Cu1.8Se at 200 °C and Cu2Se at 250 °C within 6–8 min reaction time. Transmission electron microscopy (TEM) revealed crystalline nature of as-made particles with irregular truncated morphology, which exhibit a high phase purity as identified by X-ray powder diffraction (XRPD) analysis. Temperature-dependent transport properties were characterized via electrical conductivity, Seebeck coefficient, and thermal diffusivity measurements. Subsequent to spark plasma sintering, pure Cu1.8Se exhibited highly compacted and oriented grains that were similar in size in comparison to Cu2Se, which led to its high electrical and low thermal conductivity, reaching a very high power-factor (24 µW/K−2cm−1). Density-of-states (DOS) calculations confirm the observed trends in electronic properties of the material, where Cu-deficient phase exhibits metallic character. The TE figure of merit (ZT) was estimated for the materials, demonstrating an unprecedentedly high ZT at 875 K of 2.1 for Cu1.8Se sample, followed by 1.9 for Cu2Se. Synthetic and processing methods presented in this work enable large-scale production of TE materials and components for niche applications.
45.	Hansson, Niklas, 1992 (författare) Oxidative dissolution of UO2 by α-radiolysis 2022 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract To prevent the spread of radiotoxic nuclides in the environment, spent nuclear fuel generated by decades of nuclear power operation must be safely stored for at least 100 000 years. The KBS-3 method is a highly developed deep geological repository concept and is the first final repository design for high-level nuclear waste to be constructed. It contains a number of engineered barriers designed to prevent groundwater from coming into contact with the spent nuclear fuel. However, the consequences of groundwater coming into contact with the fuel must be considered when assessing the safety of this repository concept. After ~1000 years, the initially dominant γ-emitting elements have largely decayed, and the α-emitters dominate the radiation field. At the fuel-water interface, the fuel’s strong α-radiation field causes extensive radiolysis, creating locally oxidizing conditions. The oxidants formed can cause oxidation of the UO2 matrix from the U(IV) state to the U(VI) state, significantly increasing its solubility in the process. The water intrusion also leads to anoxic corrosion of the iron inserts, forming large amounts of H2 in the process. This process has been shown to protect nuclear fuel against oxidative dissolution. The oxidative dissolution of UO2-based materials has been experimentally studied and modelled in this work. Oxidation and dissolution of UO2 pellets were studied under an external irradiation source, in both Ar and H2 atmospheres. In the Ar atmosphere, the oxidation of UO2 was shown to take place through the incorporation of a significant U(V) oxidation state fraction. In the H2 atmosphere, the surface was protected during exposure to the external irradiation source against both surface oxidation and dissolution. Very low dissolution yields were found in the study of SIMFUEL, with H2 catalytically activated on the pellet surface, efficiently causing catalytic decomposition of H2O2 without leading to oxidative dissolution of the UO2 matrix. Highly Pu-doped MOX pellets showed a strong oxidative dissolution in the Ar atmosphere. This was somewhat mitigated in the D2 atmosphere. The modelled data were shown to accurately replicate the experimental results. Dissolved U(VI) was shown to be strongly reductively precipitated on corroding iron foils under anoxic conditions. This decreased the initially dissolved concentrations by three orders of magnitude over relatively short periods. This work furthers the understanding of oxidative dissolution of UO2-based materials under α-radiation fields and the effect of reducing agents present in the canister.
46.	Kamlar, Martin, 1981, et al. (författare) Synthesis of cis-Oriented Vicinal Diphenylethylenes through a Lewis Acid-Promoted Annulation of Oxotriphenylhexanoates 2021 Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 86:13, s. 8660-8671 Tidskriftsartikel (refereegranskat)abstract This study explores the synthesis of cyclic cis-vicinal phenyl ethylenes from oxotriphenylhexanoates. The reaction is a BBr3-promoted cyclization of 1,6-ketoesters (1) to five-membered diketo compounds (2). The synthesis is interesting as it constitutes one of the few examples of modular stereoselective synthesis of structures with a cis-oriented vicinal diphenylethylene. The core structure of 2 can be smoothly derivatized, which makes it a promising synthetic building block for further stereoselective synthetic applications.
47.	Katke, C., et al. (författare) Colony-like Protocell Superstructures 2023 Ingår i: Acs Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 17:4, s. 3368-3382 Tidskriftsartikel (refereegranskat)abstract We report the formation, growth, and dynamics of model protocell superstructures on solid surfaces, resembling single cell colonies. These structures, consisting of several layers of lipidic compartments enveloped in a dome-shaped outer lipid bilayer, emerged as a result of spontaneous shape transformation of lipid agglomerates deposited on thin film aluminum surfaces. Collective protocell structures were observed to be mechanically more stable compared to isolated spherical compartments. We show that the model colonies encapsulate DNA and accommodate nonenzymatic, strand displacement DNA reactions. The membrane envelope is able to disassemble and expose individual daughter protocells, which can migrate and attach via nano tethers to distant surface locations, while maintaining their encapsulated contents. Some colonies feature "exocompartments", which spontaneously extend out of the enveloping bilayer, internalize DNA, and merge again with the superstructure. A continuum elastohydrodynamic theory that we developed suggests that a plausible driving force behind subcompartment formation is attractive van der Waals (vdW) interactions between the membrane and surface. The balance between membrane bending and vdW interactions yields a critical length scale of 236 nm, above which the membrane invaginations can form subcompartments. The findings support our hypotheses that in extension of the "lipid world hypothesis", protocells may have existed in the form of colonies, potentially benefiting from the increased mechanical stability provided by a superstructure.
48.	Kumar, P. Anil, et al. (författare) All-alkoxide based deposition and properties of a multilayer La0.67Sr0.33MnO3/CoFe2O4/La0.67Sr0.33MnO3 film 2021 Ingår i: European Journal of Inorganic Chemistry. - : John Wiley & Sons. - 1434-1948 .- 1099-1948 .- 1099-0682. ; 2021:18, s. 1736-1744 Tidskriftsartikel (refereegranskat)abstract Single and multilayer films of La0.67Sr0.33MnO3 and CoFe2O4 were deposited by spin-coating. The all-alkoxide precursors allowed inorganic gel films of extreme homogeneity to be formed and converted to phase pure complex oxides at low temperatures. La0.67Sr0.33MnO3 films were made with La- and Ca-methoxy-ethoxides and Mn19O12(moe)(14)(moeH)(10) as precursors at 800 degrees C. The CoFe2O4 films were obtained at extremely low 275 degrees C, using a new CoFe2-methoxyethoxide precursor. The decomposition and microstructural development on heating was described by TG, TEM, XRD and IR spectroscopy. XRD showed no spurious phases and the unit-cell dimensions coincided quite well with literature values of the targeted phases. The structural, magnetic and electronic properties of these films established their phase purity and high quality with physical properties comparable to films deposited by physical deposition methods. The magnetic and magneto transport results are presented for single, bi- and tri- layer structures. The magnetically soft La0.67Sr0.33MnO3 layer was exchange coupled to the magnetically hard CoFe2O4 layer, giving rise to interesting switching behaviour in magnetism and magneto-transport properties.
49.	Matsubara, Nami, et al. (författare) Cation Distributions and Magnetic Properties of Ferrispinel MgFeMnO4 2020 Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 59:24, s. 17970-17980 Tidskriftsartikel (refereegranskat)abstract The crystal structure and magnetic properties of the cubic spinel MgFeMnO4 were studied by using a series of in-house techniques along with large-scale neutron diffraction and muon spin rotation spectroscopy in the temperature range between 1.5 and 500 K. The detailed crystal structure is successfully refined by using a cubic spinel structure described by the space group Fd3¯ m. Cations within tetrahedral A and octahedral B sites of the spinel were found to be in a disordered state. The extracted fractional site occupancies confirm the presence of antisite defects, which are of importance for the electrochemical performance of MgFeMnO4 and related battery materials. Neutron diffraction and muon spin spectroscopy reveal a ferrimagnetic order below TC = 394.2 K, having a collinear spin arrangement with antiparallel spins at the A and B sites, respectively. Our findings provide new and improved understanding of the fundamental properties of the ferrispinel materials and of their potential applications within future spintronics and battery devices.
50.	Peng, X., et al. (författare) Photodissociation of particulate nitrate as a source of daytime tropospheric Cl2 2022 Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13:1 Tidskriftsartikel (refereegranskat)abstract Chlorine atoms (Cl) are highly reactive and can strongly influence the abundances of climate and air quality-relevant trace gases. Despite extensive research on molecular chlorine (Cl2), a Cl precursor, in the polar atmosphere, its sources in other regions are still poorly understood. Here we report the daytime Cl2 concentrations of up to 1 ppbv observed in a coastal area of Hong Kong, revealing a large daytime source of Cl2 (2.7 pptv s−1 at noon). Field and laboratory experiments indicate that photodissociation of particulate nitrate by sunlight under acidic conditions (pH < 3.0) can activate chloride and account for the observed daytime Cl2 production. The high Cl2 concentrations significantly increased atmospheric oxidation. Given the ubiquitous existence of chloride, nitrate, and acidic aerosols, we propose that nitrate photolysis is a significant daytime chlorine source globally. This so far unaccounted for source of chlorine can have substantial impacts on atmospheric chemistry. © 2022, The Author(s).

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