| 1. |
- Adranno, Brando, 1993-
(författare)
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In Light of Ionic Materials : A short exploration of ionic materials for light-related applications
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Ionic liquids (ILs) have been one of the most attractive classes of materials of the last decades. The reason behind this is their peculiar set of properties, which enable their possible application in several research fields. ILs are salts that exhibit a very low melting point, which has been arbitrarily defined to be below 100 °C. Due to their ionic nature, ILs have little to no vapor pressure and they often demonstrate good electrical conductivity and high thermal and electrochemical stability. In this work, the focus is directed toward the exploitation of ILs for the engineering of materials that can have a primary role in light-emitting or light-absorbing devices. Materials belonging to the first type are explored in Papers I-III, while the ones belonging to the second are tackled in Papers IV and V.There has always been a struggle to find a balance between costs and the efficiency of emitting materials for application in dedicated devices. In Papers I-III, two strategies are taken into account to address this issue. Finding inspiration from ionic complexes of Mn(II), newly designed ionic materials and ILs emitting green light are proposed as an alternative to the more expensive heavy metals-based ones such as Ir(III) and Pt(II). Coming closer to an ideal compromise of cost and performance, fully organic and extremely cheap low-melting salts based on the 8-hydroxyquinoline unit were prepared. These compounds revealed efficient fluorescence in the blue region of the spectrum for such simple molecules, paving the way for the preparation of possibly inexpensive light-emitting devices.In Paper IV, direct absorption of light is taken into consideration with photoresponsive ionic liquids, which undergo cis-trans isomerization. Due to this feature and their ionic nature, these materials could be adopted into photoswitches. Additionally, the effect of functional groups on the isomerization of the ILs and on the ability of the materials to undergo mesophase formation was studied.One of the key components of dye-sensitized solar cells is the electrolytic mediator sandwiched between two electrodes. This has been a matter of intense study due to issues regarding its stability, which impair the device's performance. ILs can be adopted in devices to solve this issue. In Paper V, triazolium ILs allowed the manufacturing of devices with higher efficiencies and longer lifetimes than the ones realized with imidazolium relatives. These materials allowed for the stability of the ionic couple I-/I3- and moisture resistance due to their non-hygroscopic nature.
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| 2. |
- Hammond, Oliver S., et al.
(författare)
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Ionic liquids and deep eutectics as a transformative platform for the synthesis of nanomaterials
- 2022
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 58:24, s. 3865-3892
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Forskningsöversikt (refereegranskat)abstract
- Ionic liquids (ILs) are becoming a revolutionary synthesis medium for inorganic nanomaterials, permitting more efficient, safer and environmentally benign preparation of high quality products. A smart combination of ILs and unconventional synthesis methods allows added value to be drawn from the broad matrix of available property combinations. Mixed systems such as Deep Eutectic Solvents (DES) offer a similarly broad combinatorial playground, which is also beginning to translate into applications. Approached holistically, these liquids therefore enable new universal manufacturing techniques that provide solutions to the existing problems of nanomanufacturing, and beyond that will open completely new horizons and possibilities for controlling the growth and assembly of nanostructures. Examples that illustrate the power of ILs in the improved manufacturing of nanomaterials are explored, such as the synthesis of light phosphors with exceptional quantum yields, record-figure-of merit thermoelectrics, and efficient photocatalysts, alongside developments in DES nanostructure and deep eutectic-solvothermal and ionothermal techniques.
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| 3. |
- Kotur, Bogdan, et al.
(författare)
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Crystal and electronic structures of a new hexagonal silicide Sc38Co144Si97
- 2022
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Ingår i: Journal of Solid State Chemistry. - : Elsevier BV. - 0022-4596 .- 1095-726X. ; 316
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Tidskriftsartikel (refereegranskat)abstract
- Sc38Co144Si97 was prepared from the elements by arc melting under argon and subsequent annealing at 800 °C for 350 h. Single-crystal X-ray diffraction reveals Sc38Co144Si97 to crystallize in a new hexagonal structure type: Pearson's symbol hP279, space group P63/m, a = 33.624(7), c = 3.639(1) Å. The crystal structure of Sc38Co144Si97 can be considered as a 2D intergrowth of three kinds of fragments of simpler structure types: hexagons and quadrilaterals with the arrangements of the Sc6Co30Si19-type and triangles with the arrangement of the Gd4Co13(Si, P)9-type. Quantum chemical calculations have been performed to analyze the electronic structure and provide deeper insight into the structure-property relationships. The Extended Hückel (EH) calculation indicates that Co in Sc38Co144Si97 adopts close to a d10 configuration owing to the covalent interaction with Si. The Sc–Co and Sc–Si interactions are more ionic, and Co–Co and Co–Si bonds are more covalent interactions.
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| 4. |
- Mishra, Manish Kumar, et al.
(författare)
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CO2 capture from ambient air via crystallization with tetraalkylammonium hydroxides
- 2022
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 51:46, s. 17724-17732
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Tidskriftsartikel (refereegranskat)abstract
- Aqueous solutions of a series of short carbon chain tetra(n-alkyl)ammonium hydroxides, [Nnnnn][OH] with n = 2: n-ethyl, 3: n-propyl, 4: n-butyl, have been serendipitously found to be potential candidates for direct air carbon capture (DAC) when being used as reagents in more complicated reactions. Aqueous solutions of [N3333][OH], [N2222][OH], or [N3333][OH] with UO2SO4·3H2O and 1,4-diamidoximylbenzene, and [N4444][OH] with cytosine (HCyt) directly absorb CO2 from the atmosphere upon mild heating in the open atmosphere crystallizing in complexes reaching up to 2 : 1 CO2/[Nnnnn]OH ratio. [N2222][HCO3]·3H2O (1), [N2222]2[H(HCO3)3]·5H2O (2), [N3333][HCO3]·0.5H2O (3), [N3333][H(HCO3)2] (4), [N3333]2[(tpa)(H2CO3)2] (5; tpa = terephthalate), [N4444][H(Cyt)(HCO3)]·H2O (6) and [N4444][H2(Cyt)2(HCO3)]·H2O (7) have been isolated in crystalline form and structurally characterized by single crystal X-ray diffraction. The compounds are characterized by complex polyanionic formations from bicarbonate dimers ([(HCO3)2·(H2O)]24−) or chains ([H(HCO3)2]nn− or [H2(tpa)(HCO3)2]n2n−) to water-bicarbonate associates ([(HCO3)2·6H2O]2− and [(H2CO3·(HCO3)2)2·6H2O·2H2O]2−) and three-component anionic layers ([H(Cyt)(HCO3)·H2O]nn− and [H2(Cyt)2(HCO3)·H2O]nn−) frequently showing proton sharing. While some hydroxides themselves can maintain a high CO2/[Nnnnn][OH] ratio, particularly 2 and 4, the presence of secondary hydrogen bond donors/acceptors may increase the sorption efficiency through decreased solubility and enhanced crystallization.
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| 5. |
- Monteiro, Bernardo, et al.
(författare)
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Lanthanide-based complexes as efficient physiological temperature sensors
- 2022
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Ingår i: Materials Chemistry and Physics. - : Elsevier BV. - 0254-0584 .- 1879-3312. ; 277
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Tidskriftsartikel (refereegranskat)abstract
- A new molecular thermometric sensor based on the terbium(III) complex [C(2)mim][Tb(fod)4] (C(2)mim - 1-methyl-3-ethylimidazolium, fod(-) - tetrakis-6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate),doped with 0.015% of its europium(III) analogue (1, [C(2)mim][Tb(fod)(4)]0.99985:[C(2)mim][Eu(fod)(4)]0.00015), was prepared and its thermochromic behaviour evaluated from ambient temperature up to 75 degrees C, including in the physiological range (35-45 degrees C). It was found that the intensity ratio of the D-5(4)-> F-7(5) (TbIII) and D-5(0)-> F-7(2) (EuIII) transitions is correlated with temperature having three different linear regimes. Visual colorimetry allowed the evaluation of the temperature in different ranges from green at ambient temperature, to yellow and finally red at higher temperatures. The TbIII complex emission intensity is extremely sensitive to small temperature variations, particularly between 25 and 35 degrees C, were it reaches only 40% of the initial intensity. Confinement of the dopped TbIII tetrakis-complex in the organic polymeric matrix poly(methylmethacrylate) (PMMA) induced higher thermal stability in 1, together with a strong temperature dependence of the most intense emissive transition of the TbIII complexes. The photoluminescence quantum yield of polymer-lanthanide hybrid materials increased significantly compared with that of 1. Under 366 nm irradiation, the hybrid material presents a green colour at 25 degrees C that evolves to yellow at 30 degrees C and to a white tone at 35 degrees C.
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| 6. |
- Ovchinnikov, Alexander, et al.
(författare)
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Flux Growth, Crystal Structures, and Electronic Properties of the Ternary Intermetallic Compounds Ca3Pd4Bi8 and Ca3Pt4Bi8
- 2022
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 61:25, s. 9756-9766
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Tidskriftsartikel (refereegranskat)abstract
- Reaction of the elements yielded Ca3Pt4Bi8 and CaPtBi, which are, to the best of our knowledge, the first reported ternary Ca–Pt–Bi compounds. The compounds crystallize isostructural to the Pd analogs Ca3Pd4Bi8 (own structure type) and CaPdBi (TiNiSi structure type), respectively. Employing a multistep temperature treatment allows for the growth of mm-sized single crystals of Ca3Pd4Bi8 and Ca3Pt4Bi8 from a Bi self-flux. Their crystal structures can be visualized as consisting of a three-dimensional extended polyanion [M4Bi8]6– (M = Pd, Pt), composed of interlinked M–Bi chains propagating along the c direction, and Ca2+ cations residing in one-dimensional channels between the chains. First-principles calculations reveal quasi-one-dimensional electronic behavior with reduced effective electron masses along [001]. Bader analysis points to a strong anionic character of the M species (M = Pd, Pt) in Ca3M4Bi8. Thus, it is more appropriate to address the compounds Ca3Pd4Bi8 and Ca3Pt4Bi8 as a palladide and platinide, respectively. Magnetization measurements indicate diamagnetic behavior with no indications for superconductivity down to 2 K. Electrical resistivity data are consistent with metallic behavior and suggest predominant electron–phonon scattering.
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| 7. |
- Pani, Marcella, et al.
(författare)
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Four ternary silicides in the La-Ni-Si system : from polyanionic layers to frameworks
- 2022
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Ingår i: CrystEngComm. - : Royal Society of Chemistry (RSC). - 1466-8033. ; 24:47, s. 8219-8228
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Tidskriftsartikel (refereegranskat)abstract
- The central part of the La–Ni–Si system has been investigated at 800 °C by means of single crystal X-ray diffraction, microscopy and analytical microprobe techniques. The result led to the identification of four new metal-rich silicides: LaNi2Si (Rm, a = 4.0263(3) Å, c = 15.066(2) Å, Z = 3), La2Ni3Si2 (P21/c, a = 6.8789(7) Å, b = 6.2167(3) Å, c = 12.214(1) Å, β = 90.92(1), Z = 4), La3Ni3Si2 (Pnma, a = 7.501(2) Å, b = 14.316(4) Å, c = 6.149(2) Å, Z = 4), La6Ni7Si4 (Pbcm, a = 6.066(1) Å, b = 7.488(1) Å, c = 29.682(5) Å, Z = 4). LaNi2Si belongs to the SrCu2Ga structure type, which is not represented among silicides, while La2Ni3Si2 crystallizes in its own structure type. Both compounds feature layered polyanionic motifs consisting of Ni and Si, which are separated by La. Instead, La6Ni7Si4 and La3Ni3Si2 are characterized by polyanionic networks. The former compound belongs to the Pr6Ni7Si4 structure type, with only two other representatives (Ce and Nd); the latter has been observed only with Rh and Ir. The two structures reveal close structural relationships having multiple identical slabs. Tight-binding electronic structure calculations by linear muffin-tin-orbital methods were performed for LaNi2Si, La2Ni3Si2 and La3Ni3Si2 to gain insights into their structure–bonding relationships. Their band structures suggest a metallic character for all compounds. The overall crystal orbital Hamilton populations are dominated by polar Ni–Si bonds, though homoatomic Ni–Ni and La–Ni(Si) bond contributions are not negligible. The variety of bonding patterns may serve as a logical explanation for the number of discovered compounds in this system as well as for the diversity of the observed structures.
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| 8. |
- Prokop, K. A., et al.
(författare)
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Nano-crystalline Nd3+-doped LuPO4 optical materials obtained by ionic liquid assisted synthesis route
- 2022
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Ingår i: Materials Science & Engineering. - : Elsevier BV. - 0921-5107 .- 1873-4944. ; 275
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Tidskriftsartikel (refereegranskat)abstract
- LuPO4 in the form of nano-powders can find potential application in bio-imaging and luminescence thermometry. To enable development of functional materials there is a need to acquire basic information about the effect of morphology and grain size on spectroscopic properties. So, we investigated a series of Nd3+-doped LuPO4 nanoparticles prepared with task-specific ionic liquid as the reactant and in-situ stabilizer. Thus, fast and facile preparation of the desired well-crystallized single-phase phosphate nanomaterials was possible. The XRD patterns and TEM analysis revealed the influence of the synthesis conditions on the morphology and nanoparticles size, which is reflected in their spectroscopic properties. Low-temperature high-resolution techniques i.e. absorption spectroscopy at 4.2 K and laser site-selective spectroscopy at 77 K with Nd3+ ion as structural probe were used. Micro-powdered Nd3+-doped LuPO4 obtained by a solid-state reaction was applied as a reference. The possible application of this material as an optical thermometer was considered.
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| 9. |
- Renier, Olivier, 1995-
(författare)
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Exploring The Versatility Of Ionic Liquids : From fundamental understanding to materials inspired from ionic liquids
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Ionic liquids (ILs) have gained popularity as “green” and safe replacements for conventional organic solvents. They are defined as ionic salts displaying a melting point below 100 °C. Some of their unique characteristics also include negligible vapour pressure, good electrical conductivity as well as good thermal and chemical stability. While their “green” nature has since been disputed, they can be used and applied in many additional fields, such as solar energy production, new lighting technology and much more. In this thesis, the aim is to gain fundamental knowledge on ILs, specifically their structures and behaviour, in order to design materials tailored for specific applications. We also aim to use ILs to access otherwise difficult to synthesize materials and study their properties and applications.The thermal properties of ILs are one of their most important characteristics. However, it is still poorly understood how the structural aspects of ILs influence their particular thermal behaviour. By studying different systems, we derived relationships between the structure and the thermal behaviour of ILs. Hydrogen bonding and other supramolecular interactions play a major role in controlling both the melting temperature and the IL's ability to support a liquid crystalline mesophase. This control was shown both in a series of ILs based on 1-alkyl-3-dodecylimidazolium bromide and in a series of ILs based on azobenzene-imidazolium compounds.The stability issues associated with the electrolytes used in dye-sensitized solar cells (DSSCs) present a major disadvantage. We tested using ILs as electrolytes to avoid this problem. In our study, we used 1,3-dialkyltriazolium ILs as electrolytes in combination with the iodide redox couple, and not only was the stability of the DSSC improved but also the performance of IL-based DSSCs.Efficient luminescent materials are always sought after. Using ILs in combination with lanthanides, we achieved highly luminescent compounds as well as some magnetic ones. ILs can also be used to access anhydrous forms of otherwise hydrophilic species, such as ions of the lanthanides. We have used acetate ILs to attain water free complexes of the ions from the whole lanthanide series, starting from the hydrated species. This simple process could be applied to more species of hydrophilic metals that are otherwise known to form hydrates.Finally, the ligand obtained through ILs, 1,3-diethylimidazole-2-thione was used to aid in the studying of phase transitions when combined with zinc chloride (ZnCl2). It helped to reveal a yet unseen amorphous step in the solid-solid phase transition from a single crystal into another one, where morphology of the particle was preserved. I forsee that more fundamental structural studies can be conducted by forcing the coordination of the soft-donor nitrogen onto lanthanides by using dicyanamide ILs in the future.
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| 10. |
- Shi, Rui, et al.
(författare)
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Phonon-Mediated Nonradiative Relaxation in Ln3+-Doped Luminescent Nanocrystals
- 2022
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Ingår i: ACS Materials Letters. - : American Chemical Society (ACS). - 2639-4979. ; 4:10, s. 1882-1903
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Forskningsöversikt (refereegranskat)abstract
- Unsatisfactory photoluminescence efficiency of Ln3+-doped nanocrystals severely restricts their practical application, which has been frequently correlated to the active phonon mediation in the system. Although the phonon-mediated nonradiative relaxation of Ln3+ has been mostly explained by the “energy gap law”, a growing body of observational anomalies raises questions about the general applicability and validity of this phonon frequency-orientated model. For that reason, an improved understanding, questioning commonly accepted views, is needed. Herein the discussion relevant to this topic is reviewed, stressing that for phonon-mediated nonradiative relaxation in Ln3+-doped nanocrystals not only a variety of effects associated with the particle surface but also impacts arising from the nanocrystal interior need to be considered. A clear awareness of these different aspects allows comprehending the delicate electron–lattice interactions in these systems, which is helpful in improving the performance of Ln3+-doped luminescent nanocrystals.
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| 11. |
- Siebeneichler, Stefanie, et al.
(författare)
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From a dense structure to open frameworks: The structural plethora of alkali metal iron fluorophosphates
- 2022
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 61:25, s. 9767-9775
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Tidskriftsartikel (refereegranskat)abstract
- By employing the pyridinium hexafluorophosphate task-specific ionic liquids 1-butyl-4-methylpyridinium hexafluorophosphate ([C4mpyr][PF6]) and 1-ethylpyridinium hexafluorophosphate ([C2pyr][PF6]) as the reaction medium, mineralizer, structure-directing agent, and, in the case of the smaller pyridinium cation, even a structural component, it was possible to obtain five new alkali metal iron phosphates featuring interconnected FeX6 octahedra and PX4 (X = F, O, or OH) tetrahedra. NaFe(PO3F)2 (1) is a dense 3D structure, RbFe(PO3F)(PO2(OH)F)(PO2(OH)2) (2) features 1D strands, (C2pyr)LiFe(PO3F)3(PO2F2)F (3) has 2D layers, and LiFe(PO3F)(PO2F2)F (4) as well as Cs0.75Fe(PO2.75(OH)0.25F)(PO2F2)2 (5) are 3D open frameworks. While in 1–2 as well as in 4 and 5, FeX6 octahedra and PX4 (X = F, O, or OH) tetrahedra alternate, 3 features octahedra dimers, Fe2X11 (X = F, O, or OH). The magnetic behavior of all compounds is governed by antiferromagnetic interactions. Interestingly, 3 exhibits a broad maximum in the temperature dependence of the magnetic susceptibility, characteristic of a low-dimensional magnetic system consistent with the presence of Fe–Fe dimers in its crystal structure.
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| 12. |
- Siebeneichler, Stefanie, et al.
(författare)
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Frustration and 120° Magnetic Ordering in the Layered Triangular Antiferromagnets AFe(PO3F)2 (A = K, (NH4)2Cl, NH4, Rb, and Cs)
- 2022
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 34:17, s. 7982-7994
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Tidskriftsartikel (refereegranskat)abstract
- A new family of oxofluorophoshates, AFe(PO3F)2 (A = K, (NH4)2Cl, NH4, Rb, and Cs), was synthesized via ionothermal methods using PF6 ionic liquids. Single-crystal and powder X-ray diffraction reveal that AFe(PO3F)2 with A = (NH4)2Cl crystallizes in a trigonal structure, while AFe(PO3F)2 with A = NH4, Rb, and Cs crystallizes in a triclinic structure. Dimorphic KFe(PO3F)2 crystallizes in both the trigonal and triclinic forms. The structures of all compounds feature Yavapaiite-like Fe(PO3F)2 slabs, which are characterized by triangular Fe layers, planar in the case of the trigonal structure and undulated in the case of the triclinic one. Magnetization measurements reveal all compounds to order antiferromagnetically at low temperatures. The trigonal phases AFe(PO3F)2 (A = K and (NH4)2Cl) display complex magnetic H–T phase diagrams. The observation of magnetization plateaus at Msat/3 (Msat = saturation magnetization) indicates the existence of the up–up–down (UUD) and V-phases at applied magnetic fields in the magnetically ordered state. Powder neutron diffraction measurements of KFe(PO3F)2 confirm the 120° spin structure at zero fields. Along c, the magnetic moments form a commensurate spiral since the spins in each plane are rotated by 90° with respect to the adjacent one. To our knowledge, this is the first time such a non-centrosymmetric version of the 120° spin structure with a 90° rotation between nearest planes has been reported.
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| 13. |
- Siebeneichler, Stefanie, 1990-
(författare)
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Magnetic frustration and low-dimensional magnetism : in transition metal fluorophosphates and square-lattice intermetallic compounds
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Solids can display a variety of vastly different magnetic properties. Besides the generally well known ferromagnets, antiferromagnets with their antiparallel arrangements of magnetic moments can exhibit a wide range of complex magnetic behavior such as magnetic frustration or low-dimensional antiferromagnetism. Magnetic frustration emerges from competing magnetic interactions and typically leads to unusual magnetic ground states such as incommensurate or non-collinear magnetic structures or spin glasses. Low-dimensional magnetic behavior occurs if the magnetic interactions within a solid become negligible in at least one dimension in space. These magnetic phenomena are not restricted to certain compound classes but commonly linked to structural features such as the magnetic ion lattice geometry or the topology of the crystal structure. Effects of magnetic frustration are most pronounced in materials with high crystal symmetries and commonly observed in antiferromagnets with certain magnetic ion lattices such as triangular or square nets. Low-dimensional magnetic interactions may arise from a spacial separation of the magnetic ions within the unit cell. Furthermore, complex magnetic properties may also arise from intricate magnetic ion lattices with unusual topologies, as it is often the case in open framework materials. This thesis focuses on the magnetic properties of a series of transition metal (T) fluorophosphates (T = Fe, Co, Ni) that display a variety of crystal structure topologies, the cubic perovskite (NH4)CoF3 as well as the intermetallic phases LaMn2(Ge1-xSix)2 and LaMn2-xAu4+x in which the Mn atoms form square nets.Ionothermal reactions, a soft-chemistry approach based on ionic liquids (ILs), was employed to synthesize the above mentioned transition metal phosphates and fluoride. Ionic liquids are salts with melting points below 100 ◦C that typically contain organic cations. Task-specific ILs may be designed to fulfill multiple purposes within an ionothermal synthesis. Thus, an IL may be the solvent, mineralizer, fluorine source and structure directing agent all in one. Thanks to the unique properties of ILs, ionothermal syntheses enable the formation of a wide range of crystal structure topologies from low-dimensional motifs to open frameworks. Furthermore, kinetics plays an important role during the crystal structure formation in an ionothermal reaction and may lead to metastable phases.Nearly all presented compounds display some type of complex magnetic behavior including magnetic frustration on the triangular and square lattices, incommensurate and/or non-collinear magnetic structures, spin glass behavior and low-dimensional magnetism of a spin dimer or chain. The magnetic properties were studied using magnetization measurements in combination with other techniques such as powder neutron and X-ray diffraction (PND, PXRD) and specific heat measurements. Temperature dependent PND measurements were employed to determine the magnetic structures and phase transitions in selected frustrated systems. A number of incommensurate and/or non-collinear arrangements of the magnetic moments including the 120◦, canted ferromagnetic, helical, conical and the so-called hedgehog spin-vortex crystal (SVC) state were observed. Density functional theory (DFT) calculations were performed to determine the total energies of possible magnetic structure solutions that cannot be distinguished from PND. Furthermore, some magnetic phase diagrams were established.
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| 14. |
- Siebeneichler, Stefanie, et al.
(författare)
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Magnetic phase diagram of the solid solution LaMn2(Ge1−xSix)2 (0 ≤ x ≤ 1) unraveled by powder neutron diffraction
- 2022
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- The structural and magnetic properties of the ThCr2Si2-type solid solution LaMn2(Ge1−xSix)2 (x = 0.0 to 1.0) have been investigated employing a combination of X-ray diffraction, magnetization and neutron diffraction measurements, which allowed establishing a magnetic composition-temperature phase diagram. Substitution of Ge by Si leads to a compression of the unit cell, which affects the magnetic exchange interactions. In particular, the magnetic structure of LaMn2(Ge1−xSix)2 is strongly affected by the unit cell parameter c, which is related to the distance between adjacent Mn layers. Commensurate antiferromagnetic layers and a canted ferromagnetic structure dominate the Si-rich part of the solid solution, whilst an incommensurate antiferromagnetic flat spiral and a conical magnetic structure are observed in the Si-poor part.
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| 15. |
- Wang, Guangmei, et al.
(författare)
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The missing link between zeolites and polyoxometalates
- 2022
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 8:46
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Tidskriftsartikel (refereegranskat)abstract
- Open framework materials such as zeolites and metalorganic frameworks are garnering tremendous interest because of their intriguing architecture and attractive functionalities. Thus, new types of open framework materials are highly sought after. Here, we present the discovery of completely new inorganic framework materials, where, in contrast to conventional inorganic open frameworks, the scaffold is not based on tetrahedral EO4 (E = main group element) but octahedral MO6 (M = transition metal) building blocks. These structural features place them closer to polyoxometalates than zeolites. The first representatives of this class of materials are [(R)24(NH4)14(PO(OH)2)6]·[M134(PO3(OH,F))96F120] (M = Co, R = C2Py = 1-ethylpyridinium and M = Ni, R = C4C1Py = 1-butyl-3-methylpyridinium) featuring interlinked fullerene-like nanosphere cavities. Having a transition metal building up the framework brings about interesting properties, for example, spin-glass behavior, and, with this particular topology, a hedgehog-like spin orientation.
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| 16. |
- Wineinger, Hannah B., et al.
(författare)
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Accessing Lanthanide Tricyanomethanide Coordination Polymers Using Ionic Liquids
- 2022
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 22:4, s. 2372-2381
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Tidskriftsartikel (refereegranskat)abstract
- In contrast to alkaline, alkaline earth, and transition metals, tricyanomethanide complexes of f-elements are largely underexplored mainly due to synthetic challenges originating from the harder Lewis acidic character of the trivalent cations; only one crystal structure of an f-element-tricyanomethanide complex has ever been reported. Here, we report that by using the tricyanomethanide-based ionic liquids (ILs) 1-butyl-4-methylpyridinium tricyanomethanide ([C4mpyrid][TCM]) or 1-ethyl-3-methylimidazolium tricyanomethanide ([C2mim][TCM]), we have identified a way to begin building a library of 1D and 2D lanthanide/tricyanomethanide coordination polymers, although not yet in an optimized, controllable fashion. Saturation of NdX3·6H2O (X = Cl– or [NO3]−) over 100 °C in [C4mpyrid][TCM] or [C2mim][TCM] followed by slow cooling allowed for the crystallization of [C2mim]n[Nd(NO3)2(μ3-TCM)(μ2-TCM)(OH2)]n (1), [C4mpyrid]2n[Nd(μ2-Cl)Cl2(μ2-TCM)(TCM)(OH2)]n (2), [C4mpyrid]n[Nd(μ2-TCM)2(TCM)2(OH2)3]n (3), and [C4mpyrid]n[NdCl2(μ2-TCM)2(OH2)2]n (4) as anionic chains (2, 4) or layers (1, 3). Compound 3 could be isolated either by saturation and heating of Nd(NO3)3·6H2O or by reheating the reaction mixture leading to 2. The use of [TCM]−-based ILs as solvent and sources of the coordinating ligand provides a method to promote f-element-[TCM]− complexation without the use of competing O-donor solvents or high temperatures, potentially opening a new route to structurally characterize [TCM]− complexes of the entire lanthanide series. Although these products were not synthesized in high yields, their isolation provides clues on how to modify and optimize the syntheses to obtain specific f-element-[TCM]− targets. This, in turn, should ultimately lead to dramatic diversification of the body of f-element-[TCM]− complexes available for study.
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