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121 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3, 4, 5, 6, 7, 8 [Next/Last]

Instruments / Technical Area	Publication Details	Published
I19-Small Molecule Single Crystal Diffraction	Quantitative Raman microscopy to describe structural organisation in hollow microcrystals built from silicon catecholate and amines Victor V. Volkov , Toby J. Blundell , Stephen Argent , Carole C. Perry Dalton Transactions DOI: 10.1039/D3DT00856H Diamond Proposal Number(s): [298766] Open Access Show Abstract ▼ Abstract: Macroscopic scale hollow microcrystals are a promising group of materials for gas and liquid uptake as well as sensing. In this contribution we describe the structure of hollow hexagonal cross-section crystals formulated as salts of a silicon catecholate anion and a tetramethylenediamine (TEMED) cation. Using a combination of X-ray single crystal diffraction, Raman spectroscopy and quantum chemistry we explore the structural properties of the hollow microcrystals. With the X-ray structural data as a starting point and assisted with quantum chemistry we compute Raman tensors to fit polarisation sensitive spectral responses and predict the orientation and packing of unit cells in respect to the long and short axis of the synthesised microcrystals. Using these newly developed methods for predicting molecular Raman responses in space with dependence on local orientation, we present the quantitative analysis of experimental Raman images of both hexagonal and tetragonal cross section hollow microcrystals formed from silicon catecholate anions using different amines as counterions. We describe the distributions of chemical components at the surfaces and edges of microcrystals, address the effect of catcholate hydrophobicity on water uptake and discuss possible strategies in chemical and post-assembly modifications to widen the functional properties of this group of environmentally friendly silicon organic framework (SOF) materials.	May 2023
I11-High Resolution Powder Diffraction	Energetics of formation and stability in high pressure steam of barium lanthanide cobaltite double perovskites Aleksandra Mielewczyk-Gryń , Shuhao Yang , Maria Balaguer , Ragnar Strandbakke , Magnus H. Sørby , Iga Szpunar , Agnieszka Witkowska , Sebastian Wachowski , Jose M. Serra , Alexandra Navrotsky , Maria Gazda Dalton Transactions 91 DOI: 10.1039/D2DT03989C Show Abstract ▼ Abstract: This study concerns energetics of formation and the stability in high water partial pressure of BaLnCo2O6−δ, (Ln = La, Pr, Nd, and Gd) (BLnC) and BaGd1−xLaxCo2O6−δ, where x = 0.2, 0.5, and 0.7 (BGLC) double perovskite cobaltites. Those materials are extensively studied due to their potential applications as a positrode in electrochemical devices. Therefore, their stability under such conditions is a key issue. All investigated materials are thermodynamically stable relative to binary oxides and exhibit strongly exothermic enthalpies of formation. Moreover, BaGd0.3La0.7Co2O6−δ and BaGd0.8La0.2Co2O6−δ remain the main perovskite structure up to 3 bars of water vapor at 400 °C. At higher steam pressure, reaching 10 bar at 300 °C, the partial decomposition to constituent oxides and hydroxides was observed. The BGLC compounds exhibit higher negative formation enthalpies in comparison to single-Ln compositions, which does not translate into higher chemical stability under high steam pressures since the BLnC series retained the main perovskite structure at higher temperatures as well as in higher water vapor pressures.	Apr 2023
B18-Core EXAFS	The influence of the Li + addition rate during the hydrothermal synthesis of LiFePO 4 on the average and local structure Michelle Thiebaut , Caren Billing , Deena Naidoo , David G. Billing Dalton Transactions 144 DOI: 10.1039/D2DT01752K Diamond Proposal Number(s): [14239] Open Access Show Abstract ▼ Abstract: A hydrothermal method was used to synthesize LiFePO4 to explore the effect of the rate of addition of the Li+ precursor to a mixture of the Fe2+ and PO43− precursors. Both the average and local structures were investigated using powder X-ray diffraction, Mössbauer spectroscopy and X-ray absorption spectroscopy. Slower addition rates led to increased oxidation of Fe2+ to Fe3+ despite purging all solutions constantly, as well as increased defects. The local structure as determined by extended X-ray absorption fine structure displayed far less variation between the samples. The formation of a Li3PO4 impurity appeared to be independent of the Li+ addition rate.	Nov 2022
I11-High Resolution Powder Diffraction	Stabilization of ammonium borohydride in solid solutions of NH4BH4-MBH4 (M = K, Rb, Cs) Jakob B. Grinderslev , Torben R. Jensen Dalton Transactions 46 DOI: 10.1039/D2DT03173F Show Abstract ▼ Abstract: Ammonium borohydride, NH4BH4, has the highest gravimetric and volumetric hydrogen density among known inorganic compounds and a fascinating rock salt type crystal structure composed of H disordered tetrahedral complexes, NH4+ and BH4−, which are interlinked by a dense network of dihydrogen bonds. Here we report the synthesis, structure and properties of solid solutions in the binary systems, NH4BH4–MBH4 (M = K, Rb, Cs), which are investigated by in situ synchrotron radiation powder X-ray diffraction and thermal and photographic analysis. Full solubility and formation of (NH4)xM1−xBH4, is observed upon cryo-mechanochemical treatment. The solid solutions stabilize NH4BH4 from T ∼68 to ∼96 °C, alter the decomposition pathway and suppress the fierce decomposition of NH4BH4. However, for increased amounts of NH4BH4 in the solid solutions, the decomposition gradually shows more resemblance to that of pristine ammonium borohydride, and the thermal stability of the solid solutions appears to decrease down the group of the alkali metal ions, i.e. decreasing from K+, Rb+ and to Cs+.	Nov 2022
I15-1-X-ray Pair Distribution Function (XPDF)	Pair distribution function analysis of the reassembly step of the assembly-disassembly-organisation-reassembly (ADOR) process Samantha Russell , Fanny N. Costa , Maria Diaz-Lopez , Russell E. Morris Dalton Transactions 5 DOI: 10.1039/D2DT03389E Diamond Proposal Number(s): [26990] Open Access Show Abstract ▼ Abstract: An in situ pair distribution function study assessing the reassembly of three IM-12 (UTL) intermediate materials to the corresponding fully connected materials. A greater level of atomic change is observed at higher temperatures for the reassembly of the fully disconnected intermediate, IPC-1P, compared to the two partially connected intermediates of IPC-2P and IPC-6P.	Nov 2022
I15-1-X-ray Pair Distribution Function (XPDF)	Characterisation of intergrowth in metal oxide materials using structure-mining: the case of γ-MnO 2 Nicolas P. L. Magnard , Andy Anker , Olivia Aalling-Frederiksen , Andrea Kirsch , Kirsten M. Ø. Jensen Dalton Transactions 119–121 DOI: 10.1039/D2DT02153F Diamond Proposal Number(s): [21791] Open Access Show Abstract ▼ Abstract: Manganese dioxide compounds are widely used in electrochemical applications e.g. as electrode materials or photocatalysts. One of the most used polymorphs is γ-MnO2 which is a disordered intergrowth of pyrolusite β-MnO2 and ramsdellite R-MnO2. The presence of intergrowth defects alters the material properties, however, they are difficult to characterise using standard X-ray diffraction due to anisotropic broadening of Bragg reflections. We here propose a characterisation method for intergrown structures by modelling of X-ray diffraction patterns and pair distribution functions (PDF) using γ-MnO2 as an example. Firstly, we present a fast peak-fitting analysis approach, where features in experimental diffraction patterns and PDFs are matched to simulated patterns from intergrowth structures, allowing quick characterisation of defect densities. Secondly, we present a structure-mining-based analysis using simulated γ-MnO2 superstructures which are compared to our experimental data to extract trends on defect densities with synthesis conditions. We applied the methodology to a series of γ-MnO2 samples synthesised by a hydrothermal route. Our results show that with synthesis time, the intergrowth structure reorders from a R-like to a β-like structure, with the β-MnO2 fraction ranging from ca. 27 to 82% in the samples investigated here. Further analysis of the structure-mining results using machine learning can enable extraction of more nanostructural information such as the distribution and size of intergrown domains in the structure. Using this analysis, we observe segregation of R- and β-MnO2 domains in the manganese oxide nanoparticles. While R-MnO2 domains keep a constant size of ca. 1–2 nm, the β-MnO2 domains grow with synthesis time.	Sep 2022
I19-Small Molecule Single Crystal Diffraction	Disentangling contributions to guest binding inside a coordination cage host: analysis of a set of isomeric guests with differing polarities Cristina Mozaceanu , Atena B. Solea , Christopher G. P. Taylor , Burin Sudittapong , Michael D. Ward Dalton Transactions 115 DOI: 10.1039/D2DT02623F Diamond Proposal Number(s): [19876, 25064, 26668] Open Access Show Abstract ▼ Abstract: Binding of a set of three isomeric guests (1,2-, 1,3- and 1,4-dicyanobenzene, abbreviated DCB) inside an octanuclear cubic coordination cage host H (bearing different external substitutents according to solvent used) has been studied in water/dmso (98[thin space (1/6-em)]:[thin space (1/6-em)]2) and CD2Cl2. These guests have essentially identical molecular surfaces, volumes and external functional groups to interact with the cage interior surface; but they differ in polarity with dipole moments of ca. 7, 4 and 0 Debye respectively. In CD2Cl2 guest binding is weak but we observe a clear correlation of binding free energy with guest polarity, with 1,4-DCB showing no detectable binding by NMR spectroscopy but 1,2-DCB having −ΔG = 9 kJ mol−1. In water (containing 2% dmso to solubilise the guests) we see the same trend but all binding free energies are much higher due to an additional hydrophobic contribution to binding, with −ΔG varying from 16 kJ mol−1 for 1,4-DCB to 22 kJ mol−1 for 1,4-DCB: again we see an increase associated with guest polarity but the increase in −ΔG per Debye of dipole moment is around half what we observe in CD2Cl2 which we ascribe to the fact the more polar guests will be better solvated in the aqueous solvent. A van't Hoff analysis by variable-temperature NMR showed that the improvement in guest binding in water/dmso is entropy-driven, which suggests that the key factor is not direct electrostatic interactions between a polar guest and the cage surface, but the variation in guest desolvation across the series, with the more polar (and hence more highly solvated) guests having a greater favourable entropy change on desolvation.	Sep 2022
I11-High Resolution Powder Diffraction	Polymorphism and solid solutions of trimethylammonium monocarboranes Jakob B. Grinderslev , Lasse N. Skov , Daniel R. Sørensen , Innokenty Kantor , Mads R. V. Jørgensen , Torben R. Jensen Dalton Transactions 59 DOI: 10.1039/D2DT02513B Diamond Proposal Number(s): [29197] Show Abstract ▼ Abstract: Metal closo-boranes have recently received significant attention as solid-state electrolytes due to their high thermal and electrochemical stability, and the weak interaction between the cat- and anion, facilitating fast ionic conductivity. Here we report a synthesis method for obtaining a novel mixed closo-carborane compound, [NH(CH3)3][(CB8H9)0.26(CB9H10)0.66(CB11H12)0.08]. The crystal structures are investigated for [NH(CH3)3][CB9H10] and [NH(CH3)3][(CB8H9)0.26(CB9H10)0.66(CB11H12)0.08], revealing that the latter forms a solid solution isostructural to [NH(CH3)3][CB9H10]. The compounds exhibit polymorphism as a function of temperature, and we report the discovery of four polymorphs of [NH(CH3)3][CB9H10] and four isostructural solid solution [NH(CH3)3][(CB8H9)0.26(CB9H10)0.66(CB11H12)0.08], along with a high-temperature decomposition intermediate of the latter. The α-polymorph is an ordered structure, with increasing amounts of disorder for the β- and γ-polymorphs, while the high temperature δ- and ε-polymorphs at T > 476 K are fully disordered on both the cation and anion site. These new compounds may be used as precursors for new types of solid-state ionic conductors.	Sep 2022
I19-Small Molecule Single Crystal Diffraction	Inside or outside the box? Effect of substrate location on coordination-cage based catalysis Atena B. Solea , Burin Sudittapong , Christopher G. P. Taylor , Michael D. Ward Dalton Transactions 51, 11277 - 11285 DOI: 10.1039/D2DT01713J Diamond Proposal Number(s): [26668] Open Access Show Abstract ▼ Abstract: In this work we compare and contrast the hydrolysis of two different aromatic esters using an octanuclear cubic Co8 coordination cage host as the catalyst. Diacetyl fluorescein (DAF) is too large to bind inside the cage cavity, but in aqueous solution it interacts with the exterior surface of the cage via a hydrophobic interaction with K = 1.5(2) × 104 M−1. This is sufficient to bring it into close proximity to the layer of hydroxide ions which also surrounds the 16+ cage surface even at modest pH values, accelerating the hydrolysis of DAF to fluorescein with kcat/kuncat (the rate acceleration for that fraction of DAF in contact with the cage surface in the equilibrium) ≈50. This is far smaller than many known examples of catalysis inside a cage cavity, but at the exterior surface it is potentially general with no cavity-imposed size/shape limitations for guest binding. In contrast 4-nitrophenyl acetate (4NPA) binds inside the cage cavity with K = 3.5(3) × 103 M−1 and as such is surrounded in solution by the hydroxide ions which accumulate around the cage surface. However its hydrolysis is actually inhibited: either because of a geometrically unfavourable geometry of the bound substrate which makes it inaccessible to surface-bound hydroxide, or because the necessary volume expansion/geometry change associated with formation of a tetrahedral intermediate cannot be accommodated inside the cavity. Any 4NPA that is free in solution as part of the equilibrium undergoes catalysed hydrolysis at the cage exterior surface in the same way as DAF, but the effect is limited by the low affinity of 4NPA for the exterior surface. We conclude that exterior-surface catalysis can be effective and potentially general; and that cavity-binding of guests can result in negative, rather than positive, catalysis.	Aug 2022
	Growth, structure, and temperature dependent emission processes in emerging metal hexachloride scintillators Cs2HfCl6 and Cs2ZrCl6 V. Mykhaylyk , S. S. Nagorny , V. V. Nahorna , P. Wang , M. D. Frogley , L. Swiderski , V. Kolomiets , L. Vasylechko Dalton Transactions 65 DOI: 10.1039/D2DT00223J Open Access Show Abstract ▼ Abstract: Crystals of metal hexachlorides Cs2MCl6 (M = Hf or Zr) have recently emerged as promising materials for scintillation applications due to their excellent energy resolution. In this work, we investigated the crystal structure and scintillation properties of Cs2HfCl6 and Cs2ZrCl6 crystals in the broad temperature range from 9 to 300 K. X-ray diffraction data confirmed the same cubic structure (space group Fm3m) for Cs2HfCl6 and Cs2ZrCl6 over the entire examined temperature range. The room temperature scintillation light yield of Cs2HfCl6 excited with a 137Cs γ-source is measured to be 24[thin space (1/6-em)]800 photons per MeV, while Cs2ZrCl6 exhibits 33[thin space (1/6-em)]900 photons per MeV resulting in energy resolutions of 5.3% and 4.5%, respectively. The alpha-to-beta ratio determined at room temperature for 5.5 MeV α-particles from an 241Am source is equal to 0.39 for Cs2HfCl6 and 0.35 for Cs2ZrCl6. The measurements of scintillation decay curves revealed complex kinetics due to delayed recombination processes. A tangible enhancement of the scintillation yield with heating is observed in the 125–150 K range. This effect is a manifestation of negative thermal quenching explained by thermal activation of trapped carriers. A model of the emission centre is proposed that consistently explains the observed changes of emission intensity with temperature in the crystals under study.	Apr 2022

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