Browsing by Author "Clegg, JK"
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- ItemAssessment of radioactive ‘Hot Particles’ and marine sediment plutonium and americium levels from the Montebello Islands, Western Australia(South Pacific Environmental Radioactivity Association, 2018-11-06) Hoffman, M; Johansen, MP; Cook, M; Howell, NR; Kleinschmidt, R; Clegg, JKThe Montebello islands are an archipelago off the Western Australian coast that to this day display an artificial radioactive legacy. The legacy is the result of nuclear testing from 1952-1956. that produced long-lived radionuclides such as americium (Am-241) and plutonium (Pu-239/240). This study investigated the extent and characteristics of radioactive contamination in marine sediments near the former Operation Hurricane and Operation Mosaic G2 detonation sites in hopes of contributing to future management strategies and updated assessment of health risks to native flora, fauna and human populations. The project was conducted with samples collected in 2015 by the Australian Nuclear Science and Technology Organisation (ANSTO) as two series; Series 1 chosen to monitor the activity from the Operation Mosaic G2 detonation and Series 2 aiming to determine residual activity from the Operation Hurricane HMS Plymouth detonation. Samples were initially sieved to separate the bulk samples into four size-based fractions for analysis of activity fractionation among sediment grain sizes. Radiation counting processes included alpha spectrometry and gamma spectrometry, back-scatter electron mode scanning electron microscopy (BEI-SEM) and photo-stimulated luminescent (PSL) autoradiography to evaluate the overall radiative status of the sediment locations and to investigate the presence of ‘hot’ particles or heterogenous dispersion of radioactivity. Both spectrometry processes revealed that Series 1 Am-241 and Pu-239/240 activity was dispersed preferentially in the two larger fractions (>500 um and 500-200 um). Activity determined as Am241 and Pu-289/240 vi/as observed across Series 2 as well but as values an order of magnitude lower. Environmental plutonium from Series 1 was present in hot particle form, specifically within particles from the more active >500 um [largest] fraction which revealed gamma emissions of the plutonium progeny Am241. imaging and subsequent analysis by BE!-SEM and energy dispersive X-ray spectroscopy (EDS) of the particles revealed that the majority of the particle material was calcium carbonate, indicative of the dominant geology at the detonation site. Study results provide insights into the radioactive characteristics of hot-particles and bulk sediments at the Montebello site. it is believed and hoped that this investigation will aid decisions on the future management of the Montebello wildlife resources and marine park management, and provide insights into potential risks and protective measures for site visitors and researchers.
- ItemDual-supramolecular contacts induce extreme Hofmann framework distortion and multi-stepped spin-crossover(Royal Society of Chemistry, 2021-01-13) Ahmed, M; Brand, HEA; Peterson, VK; Clegg, JK; Kepert, CJ; Price, JR; Powell, BJ; Neville, SMAn extended nitro-functionalised 1,2,4-triazole ligand has been used to induce considerable lattice distortion in a 2-D Hofmann framework material via competing supramolecular interactions. Single crystal X-ray diffraction analyses on [Fe3(N-cintrz)6(Pd(CN)4)3]·6H2O (N-cintrz: (E)-3-(2-nitrophenyl)acrylaldehyde) reveal a substantial deviation from a regular Hofmann structure, in particular as the intra- and inter-layer contacts are dominated by hydrogen-bonding interactions rather than the typical π-stacking arrays. Also, the 2-D Hofmann layers show an assortment of ligand conformations and local FeII coordination environments driven by the optimisation of competing supramolecular contacts. Temperature-dependent magnetic susceptibility measurements reveal a two-step spin crossover (SCO) transition. Variable temperature structural analyses show that the two crystallographically distinct FeII centres, which are arranged in stripes (2[thin space (1/6-em)]:[thin space (1/6-em)]1 ratio) within each Hofmann layer, undergo a cooperative HS ↔ HS/LS ↔ LS (HS = high spin, LS = low spin) transition without periodic spin-state ordering. The mismatch between crystallographic (2[thin space (1/6-em)]:[thin space (1/6-em)]1) and spin-state (1[thin space (1/6-em)]:[thin space (1/6-em)]1) periodicity at the HS[thin space (1/6-em)]:[thin space (1/6-em)]LS step provides key insight into the competition (frustration) between elastic interactions and crystallographically driven order. © The Royal Society of Chemistry 2021
- ItemExploring the mechanism of elastically flexible crystals by automatic analysis(International Union of Crystallography, 2021-08-14) Thompson, A; Price, JR; Smith, K; Clegg, JKA recent surge in reports of crystals exhibiting elastic flexibility has changed the way we view these materials. With potential applications in flexible electronics, in depth research is required to understand why some crystals can be tied into knots, while others shatter under an applied force. Different rationales for elastic flexibility have been proposed: many crystals have been engineered to impart flexibility through isotropic interactions, although other elastic crystals have anisotropic interactions [1]. Clearly, the different interactions present result in diverse bending mechanisms. The mechanism of flexibility in elastic crystals can be resolved on an atomic-scale by use of micro-focused synchrotron radiation [2]. By examining the localised crystal structure at multiple positions across a bent crystal, the deformations of the cell parameters can be quantified (Fig. 1). Isotropic and anisotropic crystals have been analysed using this technique to determine their respective mechanisms. Unfortunately, structural mapping quickly produces large volumes of data, and manual processing would be inefficient when there are only small changes to the data. Instead, software was developed to automatically process these datasets. It is capable of taking raw frames and providing finalised CIF files with results graphically analysed. This allows for greater insight into these elastic crystals, as more data can be analysed in a reasonable time frame. This software, CX-ASAP, consists of a series of independent modules which can be placed together into an auto-processing pipeline. The advantage of this modular approach, is the fact that it is applicable to a wider range of large crystallographic dataset analysis, such as variable temperature experiments. The main consideration of this software is the limit of computer knowledge, as there are key steps during the automation where user input is mandatory for reliable results. © The Authors
- ItemGuest removal and external pressure variation induce spin crossover in halogen-functionalized 2-D Hofmann frameworks(American Chemical Society, 2020-09-27) Brennan, AT; Zenere, KA; Brand, HEA; Price, JR; Bhadbhade, MM; Turner, GF; Moggach, SA; Valverde-Muñoz, FJ; Real, JA; Clegg, JK; Kepert, CJ; Neville, SMThe effect of halogen functionalization on the spin crossover (SCO) properties of a family of 2-D Hofmann framework materials, [Fe(II)Pd(CN)4(thioX)2]·2H2O (X = Cl and Br; thioCl = (E)-1-(5-chlorothiophen-2-yl)-N-(4H-1,2,4-triazol-4-yl)methanimine) and thioBr = (E)-1-(5-bromothiophen-2-yl)-N-(4H-1,2,4-triazol-4-yl)methanimine)), is reported. Inclusion of both the chloro- and bromo-functionalized ligands into the Hofmann-type frameworks (1Cl·2H2O and 2Br·2H2O) results in a blocking of spin-state transitions due to internal chemical pressure effects derived by the collective steric bulk of the halogen atoms and guest molecules. Cooperative one-step SCO transitions are revealed by either guest removal or the application of external physical pressure. Notably, removal of solvent water reveals a robust framework scaffold with only marginal variation between the solvated and desolvated structures (as investigated by powder and single crystal X-ray diffraction). Yet, one-step complete SCO transitions are revealed in 1Cl and 2Br with a transition temperature shift between the analogues due to various steric, structural, and electronic considerations. SCO can also be induced in the solvated species, 1Cl·2H2O and 2Br·2H2O, with the application of physical pressure, revealing a complete one-step SCO transition above 0.62 GPa (as investigated by magnetic susceptibility and single crystal X-ray diffraction measurements). © 2020 American Chemical Society
- ItemHierarchical spin-crossover cooperativity in hybrid 1D chains of Fe(II)-1,2,4-triazole trimers linked by [Au(CN)2]− bridges(John Wiley & Sons, Inc, 2021-02-04) Ezzedinloo, L; Zenere, KA; Xie, Z; Ahmed, M; Scottwell, S; Bhadbhade, MM; Brand, HEA; Clegg, JK; Hua, C; Sciortino, NF; Parker, LC; Powell, BJ; Kepert, CJ; Neville, SMForemost, practical applications of spin-crossover (SCO) materials require control of the nature of the spin-state coupling. In existing SCO materials, there is a single, well-defined dimensionality relevant to the switching behavior. A new material, consisting of 1,2,4-triazole-based trimers coordinated into 1D chains by [Au(CN)2]− and spaced by anions and exchangeable guests, underwent SCO defined by elastic coupling across multiple dimensional hierarchies. Detailed structural, vibrational, and theoretical studies conclusively confirmed that intra-trimer coupling was an order of magnitude greater than the intramolecular coupling, which was an order of magnitude greater than intermolecular coupling. As such, a clear hierarchy on the nature of elastic coupling in SCO materials was ascertained for the first time, which is a necessary step for the technological development of molecular switching materials. © 2021 Wiley-VCH GmbH
- ItemA large spin-crossover [Fe4L4]8+ tetrahedral cage(Royal Society of Chemistry, 2015-05-20) Li, L; Saigo, N; Zhang, YJ; Fanna, DJ; Shepherd, ND; Clegg, JK; Zheng, RK; Hayami, S; Lindoy, LF; Aldrich-Wright, JR; Li, CG; Reynolds, JK; Harman, DG; Li, FA large discrete face-capped tetranuclear iron(II) cage, [Fe4L4](BF4)8·n(solvent), was synthesised via metal-ion directed self-assembly. The cage is formed from a rigid tritopic ligand that incorporates chelating imidazole-imine functional groups. The cage displays temperature induced spin-crossover and LIESST effects and is amongst the largest iron(II) tetrahedral cages with such properties reported. The synthesis, structure and magnetic properties of this new metallo-cage are presented. © 2015 The Royal Society of Chemistry
- ItemRhenium(i) complexation–dissociation strategy for synthesising fluorine-18 labelled pyridine bidentate radiotracers(Royal Society of Chemistry, 2020-02-28) Klenner, MA; Zhang, B; Ciancaleoni, G; Howard, JK; Maynard-Casely, HE; Clegg, JK; Massi, M; Fraser, BH; Pascali, GA novel fluorine-18 method employing rhenium(I) mediation is described herein. The method was found to afford moderate to high radiochemical yields of labelled rhenium(I) complexes. Subsequent thermal dissociation of the complexes enabled the radiosynthesis of fluorine-18 labelled pyridine bidentate structures which could not be radiofluorinated hitherto. This rhenium(I) complexation–dissociation strategy was further applied to the radiosynthesis of [18F]CABS13, an Alzheimer's disease imaging agent, alongside other 2,2′-bipyridine, 1,10-phenanthroline and 8-hydroxyquinoline labelled radiotracers. Computational modelling of the reaction mechanism suggests that the efficiency of rhenium(I) activation may be attributed to both an electron withdrawal effect by the metal center and the formation of an acyl fluoride intermediate which anchors the fluoride subsequent to nucleophilic addition. © The Royal Society of Chemistry 2020 - Open Access
- ItemSynthesis and characterisation of new tripodal lanthanide complexes and investigation of their optical and magnetic properties(Royal Society of Chemistry, 2017-08-21) Craze, AR; Huang, XD; Etchells, I; Zheng, LM; Bhadbhade, MM; Marjo, CE; Clegg, JK; Moore, EG; Avdeev, M; Lindoy, LF; Li, FThis paper presents the synthesis of a tripodal ligand (H3L) via the Schiff base condensation of N,N-diethylsalicylaldehyde and tris(2-aminoethyl)amine. The neutral complexes of type [EuL], [GdL] and [DyL] were synthesized and characterized by FT-IR, SEM-EDS, PXRD, single crystal X-ray diffraction, CHN analysis and high resolution ESI-MS. X-ray crystallographic studies demonstrated that the heptadentate ligand incorporating a cavity pre-organized by hydrogen bonding binds the Ln(III) ions to yield a face capped octahedral coordination geometry with three-fold symmetry. Photoluminescence studies show a typical Ln(III) absorption character for the three complexes, with [EuL] demonstrating considerably stronger lanthanide-based luminescence peaks, and a Eu(III) centered luminescence lifetime of 0.144 ± 0.01 ms. Temperature/field-dependent DC and temperature/frequency-dependent AC magnetic measurements carried out for the Dy(III) complex indicated obvious magnetic anisotropy and suggested slow relaxation behaviour with considerable quantum tunnelling of the magnetization contribution. © The Royal Society of Chemistry 2017
- ItemUranium(VI) hybrid materials with [(UO2)3(µ3‐O)(µ2‐OH)3]+ as the sub–building unit via uranyl–cation interactions(John Wiley and Sons, 2016-01-14) Zhang, YJ; Clegg, JK; Lu, KT; Lumpkin, GR; Tran, TT; Aharonovich, I; Scales, N; Li, FThe hydrothermal reaction of uranyl nitrate with 1,4-benzenedicarboxylic acid (H2bdc) in the presence of strontium or potassium hydroxides and nitrates afford the formation of two new uranyl hybrid materials featuring extensive uranyl-strontium or uranyl-potassium interactions with [(UO2)3(µ3-O)(µ2-OH)3]+ as the sub-building unit. Sr1.5[(UO2)12(O)3(OH)13(bdc)4]⋅6H2O (1) contains one-dimensional (1D) uranyl oxohydroxyl ribbons made of trinuclear pentagonal bipyramidal uranyl units. The ribbons are linked together via uranyl-strontium interactions to form 2D inorganic domains which are further connected through µ4-bdc anions forming a 3D hybrid structure. This is the first reported uranyl-strontium interaction in extended hybrid solid with the shortest Sr-O−yl bond length of 2.596 (8) Å. K3[(UO2)12(O)3(OH)13(bdc)4]⋅8H2O (2) has a similar 3D hybrid structure built up through extensive K-O−yl interactions with the shortest K-O−yl bond length of 2.620 (6) Å. Raman spectroscopy has confirmed the presence of oxo-bridging (U−O−U) vibrations. Thermal stabilities and photoluminescent properties are reported. © 2016 Wiley‐VCH Verlag GmbH & Co.