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Instruments / Technical Area	Publication Details	Published
B18-Core EXAFS	Analysis of the atomic structure of CdS magic-size clusters by X-ray absorption spectroscopy Ying Liu , Lei Tan , Giannantonio Cibin , Diego Gianolio , Shuo Han , Kui Yu , Martin T. Dove , Andrei Sapelkin Nanoscale 34 DOI: 10.1039/D0NR05186A Open Access Show Abstract ▼ Abstract: Magic-size clusters are ultra-small colloidal semiconductor systems that are intensively studied due to their monodisperse nature and sharp UV-vis absorption peak compared with regular quantum dots. However, the small size of such clusters (<2 nm), and the large surface-to-bulk ratio significantly limit characterisation techniques that can be utilised. Here we demonstrate how a combination of EXAFS and XANES analyses can be used to obtain information about sample stoichiometry and cluster symmetry. Investigating two types of clusters that show sharp UV-vis absorption peaks at 311 nm and 322 nm, we found that both samples possess approximately 2[thin space (1/6-em)]:[thin space (1/6-em)]1 Cd[thin space (1/6-em)]:[thin space (1/6-em)]S ratio and have similar nearest-neighbour structural arrangements. However, both samples demonstrate a significant departure from the tetrahedral structural arrangement, with an average bond angle determined to be around 106.1° showing a bi-fold bond angle distribution. Our results suggest that both samples are quasi-isomers – their core structures have identical chemical compositions, but different atomic arrangements with distinct bond angle distributions.	Sep 2020
I15-1-X-ray Pair Distribution Function (XPDF)	X-ray total scattering study of magic-size clusters and quantum dots of cadmium sulphide Lei Tan , Alston J. Misquitta , Andrei Sapelkin , Le Fang , Rory M. Wilson , Dean S. Keeble , Baowei Zhang , Tingting Zhu , Frank S. Riehle , Shuo Han , Kui Yu , Martin T. Dove Nanoscale 437 DOI: 10.1039/C9NR06355B Diamond Proposal Number(s): [22866, 23168] Show Abstract ▼ Abstract: Four types of magic-size CdS clusters and three different CdS quantum dots have been studied using the technique of X-ray total scattering and pair distribution function analysis. We found that the CdS quantum dots could be modelled as a mixed phase of atomic structures based on the two bulk crystalline phases, which is interpreted as representing the effects of random stacking of layers. However, the results for the magic-size clusters are significantly different. On one hand, the short-range features in the pair distribution function reflect the bulk, indicating that these structures are based on the same tetrahedral coordination found in the bulk phases (and therefore excluding new types of structures such as cage-like arrangements of atoms). But on the other hand, the longer-range atomic structure clearly does not reflect the layer structures found in the bulk and the quantum dots. We compare the effect of two ligands, phenylacetic acid and oleic acid, showing that in one case the ligand has little effect on the atomic structure of the magic-size nanocluster, and in another it has a significant effect.	Oct 2019
I15-Extreme Conditions	In situ studies of materials for high temperature CO2 capture and storage Matthew Dunstan , Serena Maugeri , Wen Liu , Matthew G. Tucker , Oluwadamilola Taiwo , Belen Gonzalez , Phoebe Allan , Michael Gaultois , Paul Shearing , David Keen , Anthony Phillips , Martin Dove , Stuart Scott , John Dennis , Clare Grey Faraday Discuss. DOI: 10.1039/C6FD00047A Show Abstract ▼ Abstract: Carbon capture and storage (CCS) offers a possible solution to curb the CO2 emissions from stationary sources in the coming decades, considering the delays in shifting energy generation to carbon neutral sources such as wind, solar and biomass. The most mature technology for post-combustion capture uses a liquid sorbent, amine scrubbing. However, with the existing technology, a large amount of heat is required for the regeneration of the liquid sorbent, which introduces a substantial energy penalty. The use of alternative sorbents for CO2 capture, such as the CaO-CaCO3 system, has been investigated extensively in recent years. However there are significant problems associated with the use of CaO based sorbents, the most challenging one being the deactivation of the sorbent material. When sorbents such as natural limestone are used, the capture capacity of the solid sorbent can fall by as much as 90 mol % after the first 20 carbonation-regeneration cycles. In this study a variety of techniques were employed to understand better the cause of this deterioration from both a structural and morphological standpoint. X-ray and neutron PDF studies were employed to understand better the local surface and interfacial structures formed upon reaction, finding that after carbonation the surface roughness is decreased for CaO. In situ synchrotron X-ray diffraction studies showed that carbonation with added steam leads to faster and more complete conversion of CaO than under conditions without steam, as evidenced by the phases seen at different depths within the sample. Finally, in situ X-ray tomography experiments were employed to track the morphological changes in the sorbents during carbonation, observing directly the reduction in porosity and increase in tortuosity of the pore network over multiple calcination reactions.	Apr 2016
I15-Extreme Conditions	Diffraction study of pressure-amorphized ZrW2O8 using in situ and recovered samples David Keen , Andrew Goodwin , Matthew Tucker , Joe Hriljac , Thomas Bennett , Martin Dove , Annette Kleppe , Andrew Jephcoat , Michela Brunelli Physical Review B 83 (6), 064109 DOI: 10.1103/PhysRevB.83.064109 Show Abstract ▼ Abstract: High-energy x-ray diffraction data from a series of amorphous ZrW2O8 samples, recovered from a number of different pressures, have been measured and compared with similar data collected from a sample contained within a diamond anvil cell and measured in situ at high pressure. Samples at lower pressures are a mix of crystalline and amorphous phases, whereas those above 7 GPa (both recovered and in situ) appear to be completely amorphous. Although there are only very small changes in the diffraction data from the pure phase samples recovered from different pressures, larger changes are observed in situ as a function of pressure. However, the same structural model can be used to describe all data, albeit using different densities. This strongly suggests that the amorphous phase is undergoing nonreconstructive compression in this pressure range, without fundamental modification of the underlying topology.	Feb 2011

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