I18-Microfocus Spectroscopy
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Abstract: Benthonic fauna (earthworms, nematodes) are widely studied species in soil ecotoxicology due to their strong metal accumulation ability and potential role in terrestrial ecosystems. Study of toxic metal(loid)s behavior in benthonic fauna such as earthworms, which inhabit contaminated soils and sediments, has great significance in ecotoxicological research. This chapter reviews the uses and applications of microprobe-X-ray fluorescence to analyze toxic metal(loid)s and their distribution in benthonic fauna species including sample preparation methods and analytical conditions. The following two methods can retain the original structure of the samples: sample preparation for dehydration; and sample preparation for hydration. The chapter provides an overview of achievements in toxic elements imaging and elaborated the accumulation and storage mechanism of heavy metals through insights into distribution characteristics and behavior of toxic elements present in these species. The application areas of benthic organisms can be significantly broadened, with viable uses in phytoremediation and ecological risk assessment using microprobe-XRF imaging techniques.
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Apr 2022
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[16025]
Open Access
Abstract: Assessing element speciation and solubility control mechanisms in multi-contaminated soils poses great challenges. In this study, we examined the speciation and mechanisms controlling the solubility of As and Zn in a soil historically contaminated with As, Cu, Cr, and Zn salts used for wood preservation. The leaching behavior of dissolved species, particles, and colloids was studied in an irrigation experiment with intact soil columns. Batch experiments were used to study the solubility of dissolved species as a function of pH (2–8). The speciation of As and Zn in bulk soil and leached particles was studied with microscale X-ray fluorescence (μ-XRF) and extended X-ray absorption fine structure (EXAFS) spectroscopy. Chemical speciation and solubility were evaluated by geochemical modelling. μ-XRF of bulk soil and particles showed that As and Zn were correlated in space. Bulk- and μ-EXAFS of As and Zn, in combination with calculated ion activity products of possible As-Zn minerals, suggested a koritnigite (ZnHAsO4·H2O) phase controlling the dissolved fraction of As(V) and Zn with an apparent log Ksp of −21.9 ± 0.46. This phase lowered the solubility of As by almost two orders of magnitude in soil at pH > 5, and could therefore be of great importance at other multi-contaminated sites.
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Apr 2022
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I14-Hard X-ray Nanoprobe
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Diamond Proposal Number(s):
[20036, 22509]
Open Access
Abstract: To improve the understanding of catalysts, and ultimately the ability to design better materials, it is crucial to study them during their catalytic active states. Using in situ or operando conditions allows insights into structure–property relationships, which might not be observable by ex situ characterization. Spatially resolved X-ray fluorescence, X-ray diffraction and X-ray absorption near-edge spectroscopy are powerful tools to determine structural and electronic properties, and the spatial resolutions now achievable at hard X-ray nanoprobe beamlines make them an ideal complement to high-resolution transmission electron microscopy studies in a multi-length-scale analysis approach. The development of a system to enable the use of a commercially available gas-cell chip assembly within an X-ray nanoprobe beamline is reported here. The novel in situ capability is demonstrated by an investigation of the redox behaviour of supported Pt nanoparticles on ceria under typical lean and rich diesel-exhaust conditions; however, the system has broader application to a wide range of solid–gas reactions. In addition the setup allows complimentary in situ transmission electron microscopy and X-ray nanoprobe studies under identical conditions, with the major advantage compared with other systems that the exact same cell can be used and easily transferred between instruments. This offers the exciting possibility of studying the same particles under identical conditions (gas flow, pressure, temperature) using multiple techniques.
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Mar 2022
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I14-Hard X-ray Nanoprobe
I18-Microfocus Spectroscopy
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Abstract: This thesis focuses on the mineralogical study of altered martian meteorites and the development of a novel wet-chemistry instrument. X-ray spectroscopy and electron microscopy have been used to investigate the secondary mineralogy of martian meteorites and their associated fluids. Martian analogue brines were investigated with transmission spectroscopy in order to address the technique’s capabilities for detecting dilute, astrobiologically significant fluids.
The newly-found martian shergottite, Northwest Africa (NWA) 10416, bears a distinctive colouration in its olivine megacrysts which is suggestive of hydrous alteration. The meteorite has been petrographically characterised and the origin of its alteration has been determined as terrestrial. Oxygen isotope analysis and the observation of secondary phases within shock features using Transmission Electron Microscopy (TEM) have indicated a terrestrial fluid. Synchrotron X-ray Absorption Spectroscopy (XAS), X-ray Diffraction (XRD) and Electron Probe Micro-Analysis (EPMA) have allowed its characterisation as a low-temperature, possibly acidic, fluid.
Analysis of the martian nakhlite, Lafayette, has been performed in order to assess the extent of carbonate dissolution by a hydrothermal martian fluid. Textures determined by Scanning Electron Microscopy (SEM) and TEM, and compositions determined by EPMA and XAS have displayed the variable nature of this dissolution and allowed the identification of the mesostasis phyllosilicate as odinite. This work has illustrated a process in which martian crustal fluids can dissolve carbonates and produce substantial amounts of methane, informing our understanding of martian atmospheric methane.
The capabilities of transmission spectroscopy when detecting organic martian analogue brines have been assessed to further the development of the wet-chemistry instrument, ASPIRE. Transmission spectroscopy was unsuccessful in detecting the likely low organic concentrations (ppb) expected in potentially habitable martian aqueous environments. However, future avenues of research have been suggested for consideration, including investigation into the potential of reflectance spectroscopy and calibration of ASPIRE to mineralogical-free regions within the infrared region.
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Dec 2021
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I14-Hard X-ray Nanoprobe
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Diamond Proposal Number(s):
[23693, 23602]
Open Access
Abstract: Magnetotactic bacteria (MTB) sequester iron from the environment to biomineralize magnetite or greigite nanoparticles in magnetosome organelles, though the necessity of intracellular iron storage for the formation process is still in question. Understanding the role of iron storage would make clear the contribution of MTB in geochemical iron cycling and its potential importance during the biosynthesis of application-relevant magnetic nanoparticles. Herein, how scanning X-ray fluorescence microscopy (SXFM) and nanoscale X-ray absorption near-edge structure (nano-XANES) mapping can spatially and chemically identify intracellular iron species is reported, creating an opportunity to examine the role of iron storage in magnetite biomineralization at the single-cell level. Fe K-edge nano-XANES measurements of Magnetospirillum gryphiswaldense in varied iron media conditions and iron storage capacity reveal a significant quantity of intracellular iron heterogeneities through a distinction between formed magnetosomes and intracellular iron material. This intracellular iron component is found in both early and late stages of biomineralization. The capabilities of nano-XANES in providing an experimental advantage in the multidisciplinary field of biomineralization are highlighted.
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Dec 2021
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I14-Hard X-ray Nanoprobe
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Kyle
Frohna
,
Miguel
Anaya
,
Stuart
Macpherson
,
Jooyoung
Sung
,
Tiarnan A. S.
Doherty
,
Yu-Hsien
Chiang
,
Andrew J.
Winchester
,
Kieran W. P.
Orr
,
Julia E.
Parker
,
Paul D.
Quinn
,
Keshav M.
Dani
,
Akshay
Rao
,
Samuel D.
Stranks
Diamond Proposal Number(s):
[19023, 20420]
Abstract: Halide perovskites perform remarkably in optoelectronic devices. However, this exceptional performance is striking given that perovskites exhibit deep charge-carrier traps and spatial compositional and structural heterogeneity, all of which should be detrimental to performance. Here, we resolve this long-standing paradox by providing a global visualization of the nanoscale chemical, structural and optoelectronic landscape in halide perovskite devices, made possible through the development of a new suite of correlative, multimodal microscopy measurements combining quantitative optical spectroscopic techniques and synchrotron nanoprobe measurements. We show that compositional disorder dominates the optoelectronic response over a weaker influence of nanoscale strain variations even of large magnitude. Nanoscale compositional gradients drive carrier funnelling onto local regions associated with low electronic disorder, drawing carrier recombination away from trap clusters associated with electronic disorder and leading to high local photoluminescence quantum efficiency. These measurements reveal a global picture of the competitive nanoscale landscape, which endows enhanced defect tolerance in devices through spatial chemical disorder that outcompetes both electronic and structural disorder.
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Nov 2021
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B24-Cryo Soft X-ray Tomography
I14-Hard X-ray Nanoprobe
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Diamond Proposal Number(s):
[22696, 21505, 25824]
Open Access
Abstract: The Pt(IV) prodrug trans, trans, trans-[Pt(pyridine)2(N3)2(OH)2] (Pt1) and its coumarin derivative trans, trans, trans-[Pt(pyridine)2(N3)2(OH)(coumarin-3-carboxylate)] (Pt2) are promising agents for photoactivated chemotherapy. These complexes are inert in the dark but release Pt(II) species and radicals upon visible light irradiation, resulting in photocytotoxicity toward cancer cells. Here, we have used synchrotron techniques to investigate the in-cell behavior of these prodrugs and visualize, for the first time, changes in cellular morphology and Pt localization upon treatment with and without light irradiation. We show that photoactivation of Pt2 induces remarkable cellular damage with extreme alterations to multiple cellular components, including formation of vacuoles, while also significantly increasing the cellular accumulation of Pt species compared to dark conditions. X-ray absorption near-edge structure (XANES) measurements in cells treated with Pt2 indicate only partial reduction of the prodrug upon irradiation, highlighting that phototoxicity in cancer cells may involve not only Pt(II) photoproducts but also photoexcited Pt(IV) species.
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Nov 2021
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B18-Core EXAFS
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Diamond Proposal Number(s):
[7314, 8372, 9050]
Open Access
Abstract: Thanks to its insolubility, mineral dust is considered a stable proxy in polar ice cores. With this study we show that the Talos Dome ice core (TALDICE, Ross Sea sector of East Antarctica) displays evident and progressive signs of post-depositional processes affecting the mineral dust record below 1000 m deep. We apply a suite of established and cutting-edge techniques to investigate the properties of dust in TALDICE, ranging from concentration and grain size to elemental composition and Fe mineralogy. Results show that through acidic/oxidative weathering, the conditions of deep ice at Talos Dome promote the dissolution of specific minerals and the englacial formation of others, affecting primitive dust features. The expulsion of acidic atmospheric species from ice grains and their concentration in localized environments is likely the main process responsible for englacial reactions. Deep ice can be seen as a “geochemical reactor” capable of fostering complex reactions which involve both soluble and insoluble impurities. Fe-bearing minerals can efficiently help in exploring such transformations.
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Oct 2021
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B22-Multimode InfraRed imaging And Microspectroscopy
I14-Hard X-ray Nanoprobe
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Diamond Proposal Number(s):
[22298]
Abstract: Unwanted N2O formation is a problem that has been noted in selective catalytic reduction (SCR) where copper zeolite catalysts are utilized. With its immense global warming potential and long-term stability, elevated atmospheric N2O has already been identified as a future challenge in the war on climate change. This paper explores the phenomenon of N2O formation during NH3-SCR over Cu-SSZ-13 catalysts, which are currently commercialized in automotive emissions control systems, and proposes a link between N2O production and the local copper environment found within the zeolite. To achieve this, a comparison is made between two Cu-SSZ-13 samples with different copper co-ordinations produced via different synthesis methods. A combination of synchrotron X-ray absorption near-edge spectroscopy, UV–vis, Raman, and density functional theory (DFT) is used to characterize the nature of copper species present within each sample. Synchrotron IR microspectroscopy is then used to compare their behavior during SCR under operando conditions and monitor the evolution of nitrate intermediates, which, along with further DFT, informs a mechanistic model for nitrate decomposition pathways. Increased N2O production is seen in the Cu-SSZ-13 sample postulated to contain a linear Cu species, providing an important correlation between the catalytic behavior of Cu-zeolites and the nature of their metal ion loading and speciation.
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Oct 2021
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[24321]
Abstract: Looking for new green and environmentally friendly bio sorbents for metal removal from polluted wastewater, the present study investigates the potential new bio sorbent for Cd(II) removal from wastewater namely, the mechanism and uptake capacity of Cd(II) by brown algae, Fucus vesiculosus from the Irish Sea. This work takes a comprehensive approach involving the combination of qualitative and quantitative information collected from macro to atomistic scale, in a direct and non-destructive manner. Our results demonstrate that Cd(II) is adsorbed on the algal surface based on carboxylic of alginate groups. Effective Cd(II) adsorption is achieved at pH conditions between 5 and 7, at which the uptake occurs rapidly (∼2 h), with increasing Cd(II) concentration. Cd maximum uptake capacity (i.e., 1.203 mmol Cd g−1 dried algae) in first adsorption cycle show superior uptake as opposed to other species. Quantitatively the bio sorbent has an increasing uptake capacity (more than two folds) in the second cycle, after metal elution and biomass surface sites functioning. Desorption of Cd(II) and the regeneration of the biomass is effectively achieved with HCl (10 mM) and EDTA (1 mM), but they can only be used for two cycles, before the efficiency decreases. Microprecipitation occurs at high pH (>9) when using NaOH as an eluent. Results from this work shed new light on understanding Cd(II) binding mechanisms on Fucus v., providing crucial information for further process optimization, pilot testing, scaling up and implementation as a clean, environmentally friendly biotechnology applied to wastewater treatments.
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Oct 2021
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