Browsing by Author "Stride, JA"

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    2D cobalt based coordination polymer constructed from benzimidazole and acetate ion exhibiting spin-canted antiferromagnetism
    (Royal Society of Chemistry, 2010-05-07) Arai, L; Nadeem, MA; Bhadbhade, MM; Stride, JA
    A coordination polymer, [CoII(bIM)(acetate)] (bIM = benzimidazole) was synthesized using a solvothermal method; the complex has a two dimensional non-interpenetrated network structure and exhibits a spin-canted antiferromagnetic behaviour at low temperature and a high coercive field. © 2010, Royal Society of Chemistry
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    Application of linear spin wave theory to the Cr8 antiferromagnetic Heisenberg Ring
    (Australian Institute of Physics, 2017-02-01) D'Adam, TM; Mole, RA; Stride, JA
    The investigation of single molecule magnets (SMMs) has proven to be a focal point of magnetism research for over three decades, leading to the discovery of structures which may find applications in data storage, quantum information processing (QIP) and spintronics. Though molecular magnetism is not a new field, there are still many complexes to investigate and understand, including a range of chains, rings, discs and cages. Amongst the considerable number of structures, particular interest has been shown to antiferromagnetic Heisenberg rings (AFHR) such as Cr8, CsFe8 and Fe18. These structures have been investigated due to their interesting magnetic behaviours which include quantum tunnelling of the Neel vector (QTNV) and a long magnetic relaxation time below their blocking temperature TB [1]. The Cr8 homometallic AFHR is one of the most well understood structures of its type having been extensively investigated since its initial synthesis using techniques including high-field EPR, cantilever torque magnetometry [2] and INS [3]. Through application of Linear Spin Wave Theory (LSWT) using the SpinW Matlab library [4] it has been possible to calculate the dynamic structure factor of the Cr8 ring; this agrees well with both the INS data collected for this structure as well as models produced using alternate methods [3]. This demonstrates that LSWT is applicable to the Cr8 ring and we plan to use this method to analyse more complex structures which also do not exhibit long range magnetic ordering.
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    Application of linear spin wave theory to the Cr8 antiferromagnetic Heisenberg Ring
    (Australian Institute of Nuclear Science and Engineering, 2016-11-29) D’Adam, TM; Mole, RA; Stride, JA
    The investigation of single molecule magnets (SMMs) has proven to be a focal point of magnetism research for over three decades, leading to the discovery of structures which may find applications in data storage, quantum information processing (QIP) and spintronics. Though molecular magnetism is not a new field, there are still many complexes to investigate and understand, including a range chains, rings, discs and cages. Amongst the considerable number of structures, particular interest has been shown to antiferromagnetic Heisenberg rings (AFHR) such as Cr8, CsFe8 and Fe18. These structures have been investigated due to their interesting magnetic behaviours which include quantum tunnelling of the Neel vector (QTNV) and a long magnetic relaxation time below their blocking temperature TB [1]. The Cr8 homometallic AFHR is one of the most well understood structures of its type having been extensively investigated since its initial synthesis using techniques including high-field EPR, cantilever torque magnetometry [2] and INS [3]. Through application of Linear Spin Wave Theory (LSWT) using the SpinW Matlab library [4] it has been possible to calculate the dynamic structure factor of the Cr8 ring; this agrees well with both the INS data collected for this structure as well as models produced using alternate methods [3]. This demonstrates that LSWT is applicable to the Cr8 ring and we plan to use this method to analyse more complex structures which also do not exhibit long range magnetic ordering.
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    Band alignments of different buffer layers (CdS, Zn(O,S), and In2S3) on Cu2ZnSnS4
    (Thermo Scientific, 2014-04-01) Yan, C; Liu, F; Song, N; Ng, B; Stride, JA; Tadich, A; Hao, X
    The heterojunctions of different n-type buffers, i.e., CdS, Zn(O,S), and In2S3 on p-type Cu2ZnSnS4 (CZTS) were investigated using X-ray Photoelectron Spectroscopy (XPS) and Near Edge X-ray Absorption Fine Structure (NEXAFS) Measurements. The band alignment of the heterojunctions formed between CZTS and the buffer materials was carefully measured. The XPS data were used to determine the Valence Band Offsets (VBO) of different buffer/CZTS heterojunctions. The Conduction Band Offset (CBO) was calculated indirectly by XPS data and directly measured by NEXAFS characterization. The CBO of the CdS/CZTS heterojunction was found to be cliff-like with CBOXPS¼ 0.2460.10 eV and CBONEXAFS¼ 0.1860.10 eV, whereas those of Zn(O,S) and In2S3 were found to be spike-like with CBOXPS¼0.9260.10 eV and CBONEXAFS¼0.8760.10 eV for Zn(O,S)/CZTS and CBOXPS¼0.4160.10 eV for In2S3/CZTS, respectively. The CZTS photovoltaic device using the spike-like In2S3 buffer was found to yield a higher open circuit voltage (Voc) than that using the cliff-like CdS buffer. However, the CBO of In2S3/CZTS is slightly higher than the optimum level and thus acts to block the flow of light-generated electrons, significantly reducing the short circuit current (Jsc) and Fill Factor (FF) and thereby limiting the efficiency. Instead, the use of a hybrid buffer for optimization of band alignment is proposed. © 2014, AIP Publishing LLC.
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    Central atom size effect on the structure of group 14 tetratolyls
    (Wiley-VCH Verlag Berlin, 2009-07-06) Ng, MCC; Craig, DJ; Harper, JB; van Eijck, L; Stride, JA
    Size matters! The structure and dynamics of the tetratolyl Group 14 elements, which were probed by using high-resolution inelastic neutron scattering spectra, show a remarkable dependence on the size of the central atom. The para-methyl groups at the periphery of the molecules constitute the frontier intermolecular interactions of increasingly larger tetrahedra, which becomes critical at the molecular radius of the Si and Ge analogues. © 2009, Wiley-VCH Verlag Berlin
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    Central-atom size effects on the methyl torsions of group XIV tetratolyls
    (Wiley-V C H Verlag GMBH, 2012-10-01) Ng, MCC; Harper, JB; Stampfl, APJ; Kearley, GJ; Rols, S; Stride, JA
    The Group XIV tetratolyl series X(C6H4-CH3)4 (X=C, Si, Ge, Sn, Pb) were studied by using inelastic neutron scattering to measure the low-energy phonon spectra to directly access the methyl-group torsional modes. The effect of increased molecular radius as a function of the size of the central atom was shown to have direct influence on the methyl dynamics, reinforced with the findings of molecular dynamics and contact surface calculations, based upon the solid-state structures. The torsional modes in the lightest analogue were found to be predominantly intramolecular: the Si and Ge analogues have a high degree of intermolecular methylmethyl group interactions, whilst the heaviest analogues (Sn and Pb) showed pronounced intermolecular methyl interactions with the whole phonon bath of the lattice modes. © 2012, Wiley-VCH Verlag GmbH & Co. KGaA
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    Collective high frequency motions in liquid deuterium fluoride
    (Oldenbourg Verlag, 2008-10) Demmel, F; Heusel, G; Waldner, I; Stride, JA; Bertagnolli, H
    The collective motions in liquid deuterium fluoride (DF) have been investigated by neutron scattering motivated by a MD simulation, which predicted an optic-type mode at small momentum transfers. Spectra of the measured longitudinal current correlation function show two modes. The lower frequency one originates from acoustic-type movements. The intensity of the higher frequency excitation can be attributed to an out of phase motion of neighboring DF molecules, an optic-type mode. Both, the frequencies and the intensity distribution in momentum space agree well with the MD simulation. The widths of the experimental spectra exceed the widths from the MD simulation and indicate missing relaxation processes in the simulation. © 2008, Oldenbourg Verlag
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    Controlled synthesis of isomorphous coordination polymers via in situ ligand transformation reaction: crystal structure, thermal and magnetic properties
    (American Chemical Society, 2010-09) Nadeem, MA; Bhadbhade, MM; Bircher, R; Stride, JA
    A series of isomorphous [M2(ip)2(L)2]n (M = Co, Ni; ip = isophthalate; L = 4,4′-dipyridyl and pyrazine) coordination polymers was synthesized via in situ ligand transformation reactions, in which 1,2,3-benzene tricarboxylic acid (1,2,3-btcH3) undergoes decarboxylation to isophthalate (ip), which was found to be highly dependent on the reaction temperature. The polymers crystallize in the same crystal triclinic system P. The magnetic properties were investigated by a Quantum Design physical property measurement system (PPMS); all four compounds feature almost isostructural M(II) dimers having ferromagnetic (FM) interactions. The interdimer interactions mediated by two different carboxylate groups of ip are weak, while there is no significant magnetic exchange via the 4,4′-dipyridyl ligands along the chain direction. However, substitution with pyrazine leads to antiferromagnetic exchange of nearest neighbor dimers. © 2010, American Chemical Society
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    Controlled synthesis of titanium dioxide nanostructures
    (Trans Tech Publications, 2010-06) Stride, JA; Tuong, NT
    Recent interest in nanostructured titanium dioxide (TiO2) has been driven by the excellent photocatalytic and optical properties exhibited by the anatase and rutile phases. This article highlights the relationship between reaction conditions and the resultant nanostructured TiO2 and is primarily focused on wet chemical synthetic methods. We show that solvothermal syntheses of nano-TiO2 can be rationalised by making use of a diffusion-controlled model accounting for physical properties of the solvent such as the vapour-pressure, allowing the prediction and control the phase, size and type of nanostructured TiO2 product. This external control makes it possible for the systematic synthesis of TiO2 nanostructures via parameters such as the solvent chain length, the reaction temperature and time, and also by the addition of surfactants, providing the ability to design and tailor the nanostructured TiO2, which is vital for the optimal application of these nanostructures in photocatalytic or optical applications. © 2010, Trans Tech Publications
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    Discotic liquid crystals photovoltaic applications
    (International Conference on the Photochemical Conversion and Storage of Solar Energy, 2008-07-28) Stride, JA; Ellis, TK
    Discotic liquid crystals, arranged into columnar stacks, have shown high mobility along the aromatic core of the liquid crystalline phase.1 This property has already been exploited in other photovoltaic devices2, however maintaining the quality of the liquid crystal mesophases can be quite challenging. The concept is to control the morphology and alignment of well characterised liquid crystals, and then to polymerise the side-chains of the liquid crystals along the column in order to solidify the structure of the liquid crystal (Figure 1). The resulting polymerised liquid crystals theoretically provides a structure more suitable to charge conduction by hindering rotational and translational fluctuations.3 The project will involve much structural analysis based on wide angle 2D x-ray4, small angle x-ray and neutron scattering5, allowing us to investigate both the intracolumnar, and intercolumnar, distances of these new materials, whilst the dynamics of the fluctuations within the columns will be investigated using quasielastic neutron scattering6. These materials should have greater stability and conductivity, which will be important for potential applications in photovoltaic and other organic electronics. The hope of this project is to develop a new approach organic semiconductor technology; integrating organic conducting polymers and liquid crystal conductors, which could pave a new way of producing solution deposed organic solar cells or LED lighting.
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    Dispersive kinetics in discotic liquid crystals
    (American Physical Society, 2010-11-22) Kruglova, O; Mulder, FM; Kearley, GJ; Picken, SJ; Stride, JA; Paraschiv, I; Zuilhof, H
    The dynamics of the discotic liquid-crystalline system, hexakis (n-hexyloxy) triphenylene (HAT6), is considered in the frame of the phenomenological model for rate processes proposed by Berlin. It describes the evolution of the system in the presence of the long-time scale correlations in the system, and we compare this with experimental quasielastic neutron scattering of the molecular assembly of HAT6 in the columnar phase. We interpret the parameters of this model in terms of nonextensive thermodynamics in which rare events in the local fast dynamics of some parts of the system control the slower dynamics of the larger molecular entity and lead to a fractional diffusion equation. The importance of these rare local events to the overall dynamics of the system is linked to the entropic index, this being obtained from the data within the model approach. Analysis of the waiting-time dependence from momentum transfer reveals a Lévy distribution of jump lengths, which allows us to construct the van Hove correlation function for discotic liquid-crystalline system. © 2010, American Physical Society
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    Engineering solvothermal reactions to produce multi-walled carbon nanotubes
    (Springer, 2012-06-01) Choucair, M; Gong, B; Stride, JA
    Large multi-walled carbon nanotubes (MWCNTs) have been synthesized by the reaction of polytetrafluoroethylene and ethanol with metallic lithium under solvothermal conditions. Production of the MWCNTs depends on a series of coupled reactions that utilize the liberation of chemical energy in the thermo-dynamically closed system. Various characterization studies show tubes with diameters of 50-150 nm and micrometer lengths. The interwall spacing was found to be 0.39 +/- 0.04 nm. X-ray photoelectron spectroscopy reveals the tubes are functionalized with up to 2.2 %/wt. fluorine and 6.0 %/wt. oxygen. © 2012, Springer.
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    Enhanced reversible lithium storage in a nanosize silicon/graphene composite.
    (Elsevier, 2010-02) Chou, SL; Wang, JZ; Choucair, M; Liu, HK; Stride, JA; Dou, SX
    Si/graphene composite was prepared by simply mixing of commercially available nanosize Si and graphene. Electrochemical tests show that the Si/graphene composite maintains a capacity of 1168 mAh g−1 and an average coulombic efficiency of 93% up to 30 cycles. EIS indicates that the Si/graphene composite electrode has less than 50% of the charge-transfer resistance compared with nanosize Si electrode, evidencing the enhanced ionic conductivity of Si/graphene composite. The enhanced cycling stability is attributed to the fact that the Si/graphene composite can accommodate large volume charge of Si and maintain good electronic contact. © 2010, Elsevier Ltd.
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    A flexible copper based microporous metal-organic framework displaying selective adsorption of hydrogen over nitrogen
    (Royal Society of Chemistry, 2011-04-01) Nadeem, MA; Thornton, AW; Hill, MR; Stride, JA
    A microporous metal-organic framework [Cu-3(ipO)(2)(pyz)(2)](n), (ipO = 2-hydroxyisophthalic acid, pyz = pyrazine) was synthesized via an in situ. ligand transformation reaction. The microporous framework displays helical arrays of ipo ligands holding the Cu atoms in 2D sheets, whilst the coordination of pyz molecules acts to arrange these sheets into a microporous 3D structure. Remarkable selective sorption behaviour (>5) for H-2 over N-2 is observed and explained with molecular dynamics simulations.© 2011, Royal Society of Chemistry.
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    Four new coordination polymers constructed from benzene tricarboxylic acid: synthesis, crystal structure, thermal and magnetic properties
    (Royal Society of Chemistry, 2010-11-07) Nadeem, MA; Bhadbhade, MM; Stride, JA
    The use of 1,3,5-benzene tricarboxylic acid (H3btc) as an organic linker has allowed us to achieve the rational design of two pairs of isostructural coordination polymers having molecular formulae [M2(btc)(F)]n (M(II) = Mn (1), Co (2)) and [M3(btc)(Hbtc)(OH)(H2O)11]n (M(II) = Fe (3), Co (4)) where btc and Hbtc represent the fully and doubly de-protonated tricarboxylates respectively. These compounds were synthesized using hydrothermal methods and characterized by thermal analysis and variable temperature magnetic measurements. The X-ray analysis reveals that compounds 1 and 2 crystallize in the monoclinic space group C2/c while compounds 3 and 4 crystallize in the monoclinic space group C2. Compounds 1 and 2 feature fluoride bridged 1D metal chains linked together via carboxylate groups of btc, whilst compounds 3 and 4 consist of 1D zigzag chains having strong hydrogen bonds with neighbouring chains. Variable temperature magnetic measurements show an overall antiferromagnetic behaviour for compounds 1, 2 and 4, with no indication of magnetic ordering phenomena in the temperature range from 300–2 K. As 3 and 4 are isostructural, we assume that the magnetic properties are similar. © 2010, Royal Society of Chemistry
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    Gram-scale production of graphene based on solvothermal synthesis and sonication.
    (Nature Publishing Group, 2009-01) Choucair, M; Thordarson, P; Stride, JA
    Carbon nanostructures have emerged as likely candidates for a wide range of applications, driving research into novel synthetic techniques to produce nanotubes, graphene and other carbon-based materials. Single sheets of pristine graphene have been isolated from bulk graphite in small amounts by micromechanical cleavage(1), and larger amounts of chemically modified graphene sheets have been produced by a number of approaches(2-7). Both of these techniques make use of highly oriented pyrolitic graphite as a starting material and involve labour-intensive preparations. Here, we report the direct chemical synthesis of carbon nanosheets in gram-scale quantities in a bottom-up approach based on the common laboratory reagents ethanol and sodium, which are reacted to give an intermediate solid that is then pyrolized, yielding a fused array of graphene sheets that are dispersed by mild sonication. The ability to produce bulk graphene samples from nongraphitic precursors with a scalable, low-cost approach should take us a step closer to real-world applications of graphene. © 2009, Nature Publishing Group
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    Graphene doping to enhance the flux pinning and supercurrent carrying ability of a magnesium diboride superconductor
    (Institute of Physics, 2010-08) Xu, X; Dou, SX; Wang, XL; Kim, JH; Stride, JA; Choucair, M; Yeoh, WK; Zheng, RK; Ringer, SP
    The effect of graphene doping on the electromagnetic properties of MgB2 has been examined, in comparison with the case for undoped MgB2. It was found that graphene doping is more efficient than other forms of carbon doping for effecting improvement in the critical current density–field performance (Jc(B)), with little change in the transition temperature of MgB2. An optimal enhancement of Jc(B) was achieved for 3.7 at.% graphene doped MgB2, by a factor of 30 at 5 K and 10 T, as compared to undoped MgB2. It is found that spatial fluctuation in Tc is responsible for the flux pinning mechanism of graphene doped MgB2. © 2010, Institute of Physics
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    Increased efficiency of organic solar cells by seeded control of the molecular morphology in the active layer
    (Wiley-VCH GmbH, 2022-03-29) Rahaman, MH; Holland, J; Hossain, MA; Duan, LP; Hoex, B; Mota-Santiago, P; Mitchell, VD; Uddin, A; Stride, JA
    The performance of non-fullerene, polymer bulk heterojunction (BHJ) organic photovoltaic devices has a significant correlation with the molecular morphology of the donor and acceptor. The authors show that small organic molecules coordinated to a metal oxide, an electron transport seed layer (ETSL), can profoundly modify the donor:acceptor molecular morphology of inverted organic photovoltaic (OPV) devices. Using grazing incidence wide angle X-ray scattering (GIWAXS), the authors show that a PTB7-Th:IEICO-4F BHJ active layer has a higher degree of face-on molecular alignment on ETSL-1 (biphenyl-4,4′-dicarboxylic acid, coordinated to ZnO), whilst for naphthalene-2,6-dicarboxylic acid coordinated to ZnO (ETSL-2), it is reduced. Devices of PTB7-Th:IEICO-4F BHJ prepared on ETSL-1 had a 19.91% increase in the average power conversion efficiency (PCE), a 1.56% increase in the fill factor (FF), and a 16.66 ± 0.2% enhancement in the short circuit current density. The observed improvements are believed to be due to significant modifications to the oxide-BHJ interfacial region of ETSL-1, namely the elimination of nano-ridges and defect centers, along with an enhanced wettability. These factors can be correlated with the enhanced device performances, leading to the conclusion that the modulation of the molecular morphology of donor:acceptor blends by ETSL-1 has a broad impact on improving OPV cell efficiencies. © 2022 The Authors. Solar RRL published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution Licence
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    Inelastic neutron scattering study of K3[Mn(CN)6] in an applied field
    (Australian Nuclear Science and Technology Organisation, 2021-11-26) Stride, JA; Sulway, S; Yu, DH; Mole, RA
    A polycrystalline sample of the Mn(III) complex K3[Mn(CN)6] was measured on the cold neutron time-of-flight spectrometer Pelican at ACNS in October 2020, under a range of applied magnetic fields of 0 ≤ B ≤ 7 T. The spectra obtained in zero-field clearly show a pair of magnetic excitations centered at ca. 9.5 meV, in accord with previous measurements on IN4 at ILL and MARS at PSI. In externally applied magnetic fields, these excitations were found to be significantly modified, consistent with a Zeeman split pair of spin doublets that move apart as a function of field. This behaviour is believed to be the result of crystal field and Jahn-teller distortions of the octahedral Mn centre. © 2021 The Authors
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    Inelastic neutron scattering study of Pr2Co12Fe5.
    (Institute of Physics, 2008-03-12) Magnani, N; Paoluzi, A; Pareti, L; Stride, JA
    Inelastic neutron scattering measurements have been performed on the intermetallic compounds Pr2Co12Fe5 (and Y2Co12Fe5) on the IN4 time-of-flight spectrometer at the Institut Laue-Langevin, Grenoble. The data on the yttrium-based compound have been used to estimate the phonon scattering. A broad peak is detected at 18 meV, whose deduced Q dependence (when only the magnetic contribution is considered) is consistent with the form factor of Pr3+ ions; in the high-Q region, the same peak displays a clear phononic character. The experimental results are analysed by a molecular field model including exchange and crystal-field contributions, and the derived value for the exchange parameter is consistent with the trend inferred by studying Pr2Co17 and Pr2Fe17. A possible mechanism for the generation of the large volume magnetostriction, to be checked by further experiments, is suggested. © 2008, Institute of Physics